JP4847786B2 - Speaker system - Google Patents

Description

The present invention relates to a speaker system using an acoustic transmission path, in particular, it relates to a speaker system using an acoustic transmission path enlarged reproduction band to the low frequency side by arranging the mass elements and elastic elements alternately and periodically.

  Conventionally, as a method of expanding the reproduction band to the low frequency side, a resonance tube method using a resonance tube, a method using Helmholtz resonance using a drone cone or a port tube, and a combination of both methods are known. Yes.

  The resonance tube type speaker system is based on the principle of so-called air column resonance. According to the principle of air column resonance, it is possible to obtain a sound pressure enhancement effect due to resonance at a resonance frequency at which a sound wave emitted from the driver unit into the resonance tube becomes a standing wave.

  For example, Patent Document 1 discloses an example in which a bass enhancing effect is obtained at a frequency of a standing wave generated along an extension direction by extending a length in one direction of a cabinet to form a closed resonance tube. Yes.

  However, since the resonance tube type speaker system can resonate at a plurality of frequencies corresponding to harmonics of the fundamental resonance frequency, for example, at the same time that the bass is enhanced at the fundamental resonance frequency, There is a problem that sound pressure enhancement that causes discomfort occurs.

  Further, in a resonance tube type speaker system for low-frequency reproduction, the overall length of the resonance tube is long. In order to resonate at a desired low frequency using a resonance tube as short as possible, for example, the entire length of the resonance tube is set to a length corresponding to a quarter wavelength of a sound wave at the resonance frequency. When the velocity of sound in the air is c and the resonance frequency is f, the total length Y of the resonance tube corresponding to a quarter wavelength is given by the following equation.

  An example of a speaker system in which a resonance tube is folded is disclosed in Patent Document 2 in order to avoid an increase in overall dimensions while ensuring the acoustic total length of the resonance tube. Similar prior art is also disclosed in Patent Document 3. However, in these prior arts, not only the cabinet structure is complicated, but also the difference in inner and outer circumferences occurs in the sound path at the bent part, so that the acoustic total length of the resonance tube becomes indefinite and the resonance is inevitably lowered. Yes.

  In particular, when utilizing air column resonance equivalent to ½ wavelength, the total length of the air column resonance tube needs to be twice as long as the length given by Equation (1), for example, a sound wave having a frequency of 60 Hz. The total length of an air column resonance tube equivalent to a half wavelength that resonates with 2.8 m is a major obstacle to making the overall size of the cabinet compact, even if it is folded. Become. Therefore, in a general small speaker system for home use, it has been virtually impossible to use an air column resonance tube equivalent to a half wavelength for the purpose of enhancing a low frequency of 100 Hz or less.

  On the other hand, as a method using Helmholtz resonance, a bass reflex method (phase inversion method) using a port tube and a drone cone method using a diaphragm generally called a drone cone are known.

  In the bass reflex type speaker system, Helmholtz resonance exists in which the air in the port tube is the mass element and the air in the cabinet is the elastic element. In a bass reflex type speaker system, it is possible to enhance an acoustic signal having a low frequency by setting the Helmholtz resonance frequency low.

  The drone cone type speaker system is obtained by replacing the port tube in the bass reflex type with a diaphragm-shaped mass element (generally called a drone cone). Existence of resonance in which the drone cone is a mass element and the air in the cabinet is an elastic element is exactly the same as in the bass reflex speaker system described above.

  Patent Document 4 discloses a double bass reflex system in which two cabinets of a bass reflex system and a drone cone system are connected. As described in Patent Document 4, the double bass reflex method is a method for aiming at a stronger bass enhancement effect by causing Helmholtz resonance to act doubly.

  In addition, the means to expand the reproduction band of the speaker system as a synthetic effect of three or more different resonance frequencies by further multiplexing the resonance elements in the bass reflex and drone cone methods is known as the bandpass method. For example, it is disclosed in Patent Document 5. Port tubes or drone cones are arranged in the individual sections of the multiplexed cabinet, and the individual sections are set to have different resonance frequencies. Similar prior art is also disclosed in US Pat. In the above-described speaker system in which the resonance elements are multiplexed, a band-pass acoustic filter having a flat frequency characteristic is configured by combining resonances of different frequencies. That is, by canceling out resonance peaks of different frequencies, the frequency characteristics in the pass band are flattened compared to the case of a single resonance peak, and the apparent reproduction band is expanded.

  In the speaker system using the Helmholtz resonance as described above, it is possible to enhance the bass by setting the Helmholtz resonance frequency low. However, if an attempt is made to reduce the size of the cabinet, the aeroelasticity in the cabinet increases, the Helmholtz resonance frequency increases, and it is difficult to enhance the bass.

In order to solve such a problem in the speaker system using Helmholtz resonance, an example in which the bass is augmented by adding a resonance tube to the speaker system using Helmholtz resonance is described in Patent Document 4 above. It is disclosed in FIG. Further, FIG. 1 of the above-mentioned Patent Document 1 discloses an example in which Helmholtz resonance and resonance tube operation are combined. However, even when a resonance tube is added to the speaker system using the Helmholtz resonance, the total length of the resonance tube increases according to the equation (1). As a result, there was no change in the overall dimensions.
JP-A-5-284586 US Pat. No. 5,373,564 JP-A-7-131879 JP-A-7-203576 Japanese Patent Laid-Open No. 5-14988 JP-T-2003-523673 Japanese Patent Laid-Open No. 5-199581

  The present invention has been made paying attention to the problems as described above, and the problem is to provide an acoustic transmission path with a shortened acoustic total length. It is to provide a speaker system that can expand the reproduction band to the low frequency side while keeping the overall size compact by using it.

  The present invention for solving the above-described problems and achieving the object has the following configuration.

(1) The speaker system of the present invention has a tubular body portion having an axial length larger than the inner diameter and at least one end opened, and a mass in the axial direction of the tubular body portion inside the tubular body portion. And an acoustic vibration part in which elements and elastic elements are alternately arranged, and the sound propagating through the acoustic vibration part inside the tubular body part due to the periodicity of the arrangement of the mass element and the elastic element An acoustic transmission path in which a vibration propagation speed is 1/3 or less of the sound speed in the atmosphere in a frequency range of 20 Hz to 200 Hz; and an electroacoustic exchanger acoustically coupled to the acoustic transmission path. It is characterized by.
(2) In the speaker system according to (1), the electroacoustic exchanger is acoustically coupled to the acoustic transmission path so as not to divide the inside of the tubular body portion in the axial direction of the tubular body portion. Is desirable.
(3) In the speaker system according to (2), the electroacoustic exchanger transmits the acoustic signal in the middle of the arrangement of the mass element and the elastic element so as not to divide the arrangement of the mass element and the elastic element. Desirably acoustically coupled to the road.
(4) In the speaker system according to (3), it is preferable that both ends of the tubular body portion are open, and the mass elements are disposed at both ends of the tubular body portion.
(5) In the speaker system according to (4), a standing wave of the acoustic vibration having an axial length substantially ½ wavelength is established in the tube body portion. Is desirable.
(6) In the speaker system of (4), the elastic element is an air chamber provided inside the tube body, and three or more partitioned air chambers are arranged in series. desirable.
(7) In the speaker system according to (6), an odd number of the air chambers are arranged in series, and the electroacoustic exchanger is disposed in an air chamber arranged in a central portion of the odd number of air chambers. It is desirable that they are combined.

  According to the speaker system of the present invention, due to the periodicity of the arrangement of the mass elements and the elastic elements, the propagation speed of the acoustic vibration propagating through the acoustic vibration section inside the tubular body section is 20 Hz or more and 200 Hz or less. Since it becomes 1/3 or less of the sound speed in the air in the frequency range, it is possible to expand the reproduction band to the low frequency side while keeping the overall size compact compared to the conventional speaker system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a sectional view of an acoustic transmission line according to the first embodiment of the present invention. The acoustic transmission path 10 according to the present embodiment includes a tube portion 1 and an acoustic vibration portion.

  The acoustic vibration part includes diaphragms 3 a, 3 b, 3 c, 3 d (hereinafter sometimes collectively referred to as “vibration plate 3”) provided so as to be vibrated inside the tube part 1, and the tube part 1. Air chambers 4a, 4b, and 4c (hereinafter sometimes collectively referred to as “air chamber 4”) that are partitioned from each other inside. Here, the diaphragm 3 functions as a mass element, and the air in the air chamber 4 functions as an elastic element. The diaphragm 3 and the air chamber 4 are alternately and periodically arranged along the axial direction of the tubular body portion 1. Therefore, acoustic vibration parts 3 and 4 are configured in which mass elements and elastic elements are alternately and periodically arranged along the axial direction of the tube body part 1.

  The acoustic vibration unit is configured to propagate a predetermined acoustic vibration wave (hereinafter referred to as “element vibration”) different from a normal sound wave propagating in the atmosphere. The acoustic vibration unit is configured to reduce the propagation speed of propagating acoustic vibration, that is, element vibration, to 1/3 or less of the sound velocity in the atmosphere in a frequency range of 20 Hz to 200 Hz. Details of the acoustic vibration unit will be described later.

  As described above, the acoustic transmission path 10 according to the present embodiment is roughly divided into elements such as the tube portion 1, the diaphragm 3, and the air chamber 4. Hereinafter, each element will be described.

  The tube part 1 is a cylindrical tube, for example. The tube part 1 is configured to have an axial length (hereinafter referred to as a full length) larger than the inner diameter.

  The tube part 1 of this embodiment is open at both ends, in other words, both ends are open ends 9. Specifically, end walls 5 a and 5 b having openings are provided at both ends of the tubular body portion 1. In addition, partition walls 6 a and 6 b are provided on the inner surface of the tube portion 1. In the present embodiment, the total length of the tubular body portion 1 is 3L, and the partition walls 6a and 6b are arranged at equal intervals from the end of the tubular body portion 1 at distances L and 2L, respectively.

  In addition, from the viewpoint of facilitating assembly of the acoustic transmission path 10, the tubular body portion 1 may be formed into a tubular shape by combining a plurality of modules divided along the axis, and is divided along the axis perpendicularly. Of course, the pipe shape may be formed by combining the modules.

  Next, the diaphragm 3 will be described. The diaphragm 3 is disposed on each end wall 5a, 5b and each partition wall 6a, 6b of the tube portion 1 via an edge member 7. Therefore, in this embodiment, since both ends of the tube part 1 are the open ends 9, the diaphragms 3a and 3d, which are mass elements, are arranged at both ends of the tube part 1. The edge member 7 that supports the diaphragm 3 supports the diaphragm 3 so as to vibrate, and is made of a flexible material such as rubber or urethane foam resin and can be easily deformed. As a result, each diaphragm 3 can vibrate in the axial direction of the tube portion 1 within the range of deformation of the edge member 7. Since each diaphragm 3 is arranged to swing in the axial direction of the tubular body portion, the element vibration propagates in the tubular body portion 1 as a plane wave. For example, when at least one diaphragm is attached to be inclined with respect to the axial direction of the tube portion 1, energy is distributed to propagation modes other than simple plane waves. Resonance due to the reciprocating wave is weakened.

  As the material of the diaphragm 3, for example, similarly to the diaphragm of a general driver unit (electroacoustic exchanger), a highly rigid and lightweight material such as a metal thin plate, a resin fiber woven fabric, and high density paper can be used. . The shape of each diaphragm 3 may be a non-planar shape such as a cone or a hemisphere to ensure strength, but energy is distributed to propagation modes other than simple plane waves generated by the amplitude of the diaphragm. The resonance due to the reciprocating wave in the full length direction of the body part 1 is weakened. Note that the diaphragm 3 has a shape having a length in the front-rear direction, such as a conical shape, and the front end of the diaphragm 3 is supported by the edge member 7 as in a normal speaker unit, while the rear end of the diaphragm 3 It is desirable to suppress unnecessary motion such as vibration of the vibration shaft and rotation by adding an elastic support means such as a damper in the vicinity.

  In addition, if the effective vibration area of each diaphragm 3 is extremely small compared to the cross-sectional area inside the tube portion 1, the wave generated by the vibration of each diaphragm 3 becomes close to a spherical wave. The effective vibration area is preferably 25% or more of the cross-sectional area inside the tubular body portion 1, more preferably 50% or more of the cross-sectional area inside the tubular body portion 1. On the other hand, as will be described later, from the standpoint of enhancing the effect of reducing the propagation speed of the acoustic vibration of the acoustic vibration part as compared with the speed of sound in the atmosphere, the effective vibration area of each diaphragm 3 is reduced within the tube part 1. It is desirable that it is 75% or less of the area.

  The mass of the plurality of mass elements, that is, the diaphragm 3 may all be the same, but the mass ratio between the diaphragms 3, that is, the ratio of the maximum mass to the minimum mass of the diaphragm 3 is 1 to 3. It can also be changed within the range. For example, at least one mass element can be configured to be lighter than other mass elements. For example, in order to correct the influence due to the finite number of diaphragms 3 and air chambers 4, diaphragms 3 a and 3 d which are mass elements arranged at one end or both ends of the tubular body portion 1 It can also comprise so that it may have the mass of 0.5-1 times the mass of the diaphragms 3b and 3c which are mass elements arrange | positioned inside the part 1. FIG.

  Next, the air chamber 4 will be described. The air chamber 4 is an air chamber inside the tubular body portion 1, and in this embodiment, the internal space of the tubular body portion 1 is partitioned into three air chambers 4a, 4b, and 4c by partition walls 6a and 6b. . Therefore, the air chambers 4 a, 4 b, 4 c are arranged in series along the axis of the tube part 1. As described above, the diaphragms 3 are disposed on both sides of each air chamber 4. As a result, the acoustic transmission path of the present embodiment is configured in which the diaphragm 3 as a mass element and the air chambers 4 containing air as an elastic element are alternately and periodically arranged.

  The operational effects of the acoustic transmission path of the present embodiment configured as described above will be described.

  The schematic diagram shown in the upper part of FIG. 2 shows the simplest mechanical model corresponding to the acoustic transmission path of the present embodiment, and the lower part of FIG. 2 shows elements that are waves that propagate through this mechanical model. This shows the state of vibration. Specifically, the diaphragm 3 in the acoustic transmission path of the present embodiment corresponds to the mass point, and the air in the air chamber 4 corresponds to the spring.

  The acoustic transmission path 1 according to the present embodiment propagates a wave having a reduced propagation speed due to the periodicity of the arrangement of the mass elements and the elastic elements based on the principle described below.

As shown in FIG. 2, the simplified mechanical model corresponding to the acoustic transmission line of the present embodiment has a constant vibration element in which the mass point of mass m is a mass element and the spring having a spring constant S is an elastic element. Is a series vibration element system arranged with a period L of. When a displacement amount from the n-th material point of equilibrium position and u _n, the equation of motion,

  Can be written. The mathematical formula (2) is

  It has a traveling wave type solution. Here, k is the wave number, x is the position coordinate along the arrangement direction of the mass point and the spring, and ω is the angular frequency.

  The wave propagating in the model of FIG. 2 as represented by the mathematical formula (3), that is, the element vibration shows a completely different behavior from a normal sound wave propagating in the air in a normal cabinet. Formula,

  And the dispersion relation obtained by substituting the mathematical formula (3) into the mathematical formula (2),

  To be understood through.

  In the equation (6), ω monotonously increases with respect to the wave number k,

  Takes the maximum value. The numerical formula (7) corresponds to the fundamental resonance frequency of each vibration element as a single unit, and the element vibration having a higher frequency cannot propagate. This is because each vibration element having a length L (consisting of a mass point and a spring in the region of L / 2 on both sides thereof) is the minimum vibration unit in the acoustic transmission path of FIG. This corresponds to the fact that the element vibration of the wavelength 2L (wave number π / L) in which the element moves in the reverse direction is the propagation mode of the shortest wavelength (that is, the maximum wave number), and the element vibration of a shorter wavelength cannot propagate. The graph shown in the lower part of FIG. 2 shows the displacement of each element vibration whose wave numbers are π / L, π / 2L, π / 3L, and π / 4L with respect to the positions of the mass points 1A, 1B, 1C, 1D, and 1E. It is plotted in correspondence, and it can be understood from this graph that the wavelength of the element vibration cannot take a value shorter than 2L.

  In addition, while the velocity of sound in the air is almost constant, the phase velocity Vp of the element vibration is

  As shown, it changes depending on the value of the mass m and the spring constant S. As a result, by appropriately setting the values of the mass m and the spring constant S, the phase velocity Vp can be set lower than the sound velocity in the atmosphere, for example.

  Further, the equation (8) indicates that the phase velocity Vp varies depending on the frequency, and the maximum value of the phase velocity Vp is

  It is shown that.

  According to the mechanical model corresponding to the acoustic transmission path of the present embodiment as described above, a wave having a wavelength shorter than 2L (twice the distance between adjacent mass points) does not substantially propagate, and the phase velocity Behaves completely different from ordinary sound waves propagating in the atmosphere in that Vp varies depending on the value of mass m and spring constant S, and that phase velocity Vp has frequency dependence. It can be said that element vibration is propagated.

  Based on the above mechanical model, the operation and effect of the acoustic transmission path 10 of the present embodiment will be described.

  In the acoustic transmission path 10 shown in FIG. 1, each diaphragm 3 is a mass element that can swing in the axial direction of the tubular body portion 1, and corresponds to the mass point in FIG. 2. Further, the air inside each air chamber 4 formed by being divided by each diaphragm 3 is an elastic element and corresponds to the spring in FIG.

  For example, when the outermost diaphragm 3a or 3d is excited by an external sound wave, the vibration of the diaphragm 3a or 3d propagates in the tube portion 1 as the element vibration described above. At this time, the element vibration having a wavelength with the open ends 9 on both sides of the tubular body portion 1 as an antinode becomes a standing wave in the tubular body portion 1 and resonates with an external sound wave having the same frequency. That is, the diaphragm 3a or 3d corresponds to an opening in the air column resonance tube, and the acoustic transmission path 10 of the embodiment of FIG. 1 is configured as a resonance tube open at both ends.

  As shown in FIG. 1, the tube portion 1 of the acoustic transmission path 10 of the present embodiment is set to have a sufficiently large total length of the tube portion 1 compared to the inner diameter (diameter) of the tube portion 1. Accordingly, the propagation mode of the element vibration in the tubular body portion 1 is dominated by plane waves propagating in the full length direction of the tubular body portion 1. It is important for obtaining strong resonance without dissipating energy to other propagation modes that the element vibration is like a plane wave in the tube portion 1. For example, unlike the present embodiment, when the total length of the tube body portion 1 is set smaller than the inner diameter of the tube body portion 1, energy is distributed to the cylindrical wave mode that propagates in the tube body portion 1 in the radial direction. Therefore, the resonance due to the reciprocating wave in the full length direction of the tube part 1 is weakened.

  Further, in the present embodiment, as shown in FIG. 1, each diaphragm 3 is perpendicular to the axis of the tube part 1, and each diaphragm 3 is arranged to swing in the axis direction of the tube part 1. Therefore, the element vibration propagates in the tube portion 1 as a plane wave. For example, unlike this embodiment, when at least one diaphragm is attached to be inclined with respect to the axis of the tube body portion 1, energy is distributed to propagation modes other than simple plane waves. The resonance due to the reciprocating wave in the full length direction of the body part 1 is weakened.

  Moreover, when the shape of the diaphragm 3 of the present embodiment is formed in a flat plate shape, the element vibration can propagate through the tube portion 1 as a plane wave without disturbing the flatness of the wavefront by the diaphragm shape. it can. In this regard, when at least one diaphragm 3 has a non-planar shape such as a cone or a hemisphere, energy is distributed to propagation modes other than simple plane waves generated by the amplitude of the diaphragm 3, and therefore the tube portion The resonance due to the reciprocating wave in the full length direction of 1 is weakened.

  If the effective vibration area of each diaphragm 3 is extremely small compared to the cross-sectional area of the tube portion 1, the wave generated by the amplitude of each diaphragm is close to a spherical wave. In order for the vibration to be a plane wave, the effective vibration area of each diaphragm is preferably 25% or more, more preferably 50% or more of the cross-sectional area inside the tube portion 1.

The acoustic transmission line of the present embodiment shown in FIG. 1 replaces the mass point m in the simplified model of FIG. 2 with the mass m ₀ of the diaphragm 3 and replaces the spring S with the elasticity S ₁ of the air in the air chamber 4. However, considering the spring constant S ₀ of the edge member 7 and the mass m ₁ of air in the air chamber 4 as parasitic elements, the dispersion relationship of the acoustic transmission path of the present embodiment is as follows. ,

  And the phase velocity Vp is

  It becomes. Here, A: cross-sectional area inside the tube part 1 κ: volumetric modulus of air ρ: density of air

  For example, the tube portion 1 is a cylindrical tube having an inner diameter of 0.12 m, and a drone cone comprising a vibration system of a driver unit having a typical nominal diameter of 0.08 m (effective diameter 0.064 m) is used as a vibration plate. When arranged at intervals of 15 m, each parameter value can be set as follows.

A: 0.0113 m ² L: 0.15 m m ₀ : 2 g S ₀ : 790 N / m κ: 141700 N / m ² ρ: 1.29 kg / m ³
If the effective vibration area of the diaphragm 3 is a, the elasticity of the air chamber 4 acting on the diaphragm 3 decreases in proportion to (a / A) ² . That is, setting the effective vibration area a of the diaphragm 3 to be smaller than the cross-sectional area A inside the tube body 1 substantially reduces the elasticity of the air chamber 4 acting on the diaphragm 3, and the tube section. 1 has the effect of reducing the propagation speed of element vibration propagating in the element 1. Therefore, for example, by making the effective vibration area a of the diaphragm 3 which is a mass element be 75% or less of the cross-sectional area A inside the tube portion 1, the element vibration propagating in the tube portion 1 is obtained. The effect of reducing the propagation speed of can be sufficiently exhibited.

Here, in consideration of the fact that the effective vibration area of a typical driver unit having a diameter of 0.08 m is 0.0032 m ² , and thus occupies 28.4% of the inner cross-sectional area A of the tube body portion 1, When corrections are made to 10) and (11), the frequency of element vibration at the shortest propagateable wavelength 2L (wave number π / L) is calculated as 241 Hz, and the phase velocity Vp is calculated as 72.3 m / s. Similarly, the frequency of element vibration at a wavelength of 6 L (wave number π / 3 L) is 120 Hz, and the phase velocity Vp is calculated to be 108.4 m / s, which is about 1/3 of the speed of sound in the atmosphere. The Thus, with the acoustic transmission line according to the present invention, it is possible to easily obtain a low propagation speed of 1/3 or less of the sound speed in the atmosphere.

  The mathematical formulas (10) and (11) are used to perform approximate prediction on the assumption of an infinitely simplified model of acoustic vibration element array, and an acoustic transmission path is actually defined by a finite number of acoustic vibration elements. In the case of configuring, it is necessary to appropriately correct the mathematical formulas (10) and (11) or the calculation result based on the mathematical expressions (10) and (11).

For example, in FIG. 1, the diaphragms 3b and 3c positioned in the middle of the transmission path have air chambers that are elastic elements on both sides of the diaphragm, whereas the open end of the transmission path, that is, the opening As for the diaphragms 3a and 3d located on the end walls 5a and 5b having the above, since the air chamber on one side is absent, the spring constant is almost halved. Therefore, in the vibration element located at the open end, the frequency of the element vibration is reduced to about ^{2-1 /} 2 in the minimum case as compared with the equations (6) and (7). As a result, for example, the element vibration having the frequency of the above formula (7) that can be propagated in the other vibration element located in the middle of the transmission line propagates in the vibration element located at the open end 9 where the resonance frequency is lowered. A mismatch occurs that does not satisfy the condition, that is, the wavelength is shorter than 2L.

  In order to reduce such mismatching, the mass of the diaphragms 3a and 3d located at the open end 9 may be reduced to cancel the decrease in the spring constant. That is, by reducing the mass of the diaphragms 3a and 3d located at the open end 9 and appropriately setting it within a range of 1 to 1/2 times the mass of the diaphragms 3b and 3c located in the middle of the transmission path. All the vibration elements belonging to the transmission line including the end portions can be adjusted to be tuned to substantially the same frequency.

  As described above, according to the acoustic transmission path of the present embodiment, the following effects can be obtained.

  An acoustic vibration unit is configured by alternately arranging the diaphragm 3 as a mass element and the air chamber 4 as an elastic element, and propagates through the acoustic vibration unit due to the periodicity of the arrangement of the mass element and the elastic element. It becomes easy to set the propagation velocity (phase velocity Vp) of the element vibration to be lower than the sound velocity in the atmosphere according to the equation (8). In particular, a low propagation speed of 1/3 or less of the speed of sound in the atmosphere can be easily obtained according to Equation (8). For this reason, even if it is a pipe part with a short physical full length, the low-pitched sound reinforcement effect equivalent to a long full length pipe part can be acquired.

  Further, since the internal space of the tubular body portion 1 is divided by the diaphragms 3b and 3c arranged along the axial direction of the tubular body portion 1, element vibration having a wavelength shorter than 2L does not substantially propagate. Therefore, it is possible to selectively transmit only low-frequency acoustic vibration while suppressing unnecessary medium-high frequency acoustic vibration.

  Since the tubular body portion 10 has a length in the axial direction larger than the inner diameter, the plane wave propagating in the axial direction of the tubular body portion 1 can be made to be in a dominant state as compared with the cylindrical wave. Therefore, it is possible to prevent energy from being dissipated to other propagation modes such as a cylindrical wave.

  By arranging each diaphragm 3 that is a mass element to vibrate in the axial direction of the tubular body portion 1, the element vibration can be propagated as a plane wave in the tubular body portion 1, and the axial direction of the tubular body portion 1 can be increased. It is possible to prevent the resonance caused by the reciprocating wave from weakening.

  In addition, when each diaphragm 3 which is a mass element is formed in a flat plate shape, the element vibration propagates in the tubular body portion 1 as a plane wave without disturbing the flatness of the wave front due to the diaphragm shape. It is possible to prevent energy from being distributed to a propagation mode other than a simple plane wave generated by the amplitude of the plate 3 and to prevent the resonance due to the reciprocating wave in the full length direction of the tube part 1 from being weakened.

  When the effective vibration area of each diaphragm 3 which is a mass element is 25% or more, preferably 50% or more, of the cross-sectional area inside the tube portion 1, waves generated by the vibration of each diaphragm 3 are generated. It can prevent becoming close to a spherical wave.

  By making the effective vibration area of each diaphragm 3 that is a mass element 75% or less of the cross-sectional area inside the tube portion 1, the effect of reducing the propagation speed of element vibration propagating in the tube portion 1 is obtained. Rise.

Diaphragms 3a and 3d, which are mass elements arranged at the open end of the tube part 1, have a mass 0.5 to 1 times that of the diaphragms 3b and 3c, which are mass elements arranged inside the pipe part 1. When the configuration is such that there is a finite number of diaphragms 3 and air chambers 4, the influence of the finite number of diaphragms 3 and air chambers 4 is corrected, and the diaphragm 3 and the air that are all vibration elements including the ends and belonging to the transmission path The air in the chamber 4 can be adjusted to tune to substantially the same frequency.
(Second Embodiment)
FIG. 3 is a cross-sectional view of an acoustic transmission path according to the second embodiment of the present invention. In addition, in the acoustic transmission path of this embodiment, the point that one end of the tube part is closed by the closed end wall surface, the length (full length) in the axial direction of the tube part is 2L, and the number of diaphragms The configuration is the same as that of the acoustic transmission path of the first embodiment shown in FIG. 1 except that the number is two and the number of air chambers is two. Therefore, the same reference numerals are used for similar configurations, and repeated description is omitted.

  One end of the tube portion 1 of the present embodiment is closed, in other words, one end is a closed end 8. Specifically, a closed end wall is provided at one end of the tube part 1. On the other hand, the other end of the tube part 1 is open, in other words, an open end.

  The diaphragm 3 a is provided at the other end of the tube body 1, that is, at the open end of the tube body 1. In the present embodiment, the entire length of the tubular body portion 1 is 2L, and the diaphragm 3b is provided at a distance L from the open end of the tubular body portion 1. In addition, the diaphragm 3a and the diaphragm 3b can be arrange | positioned through the edge member 7 in the edge part wall 5, the partition, etc. similarly to 1st Embodiment. As a result, the diaphragm 3a and the diaphragm 3b can vibrate in the axial direction of the tube portion 1 respectively.

  In addition, in order for the acoustic vibration propagating through the acoustic vibration portion to propagate in the tube portion 1 as a plane wave, the inner side surface of the closed end wall is a plane, and the shapes of the diaphragms 3a and 3b are flat. It is desirable to be. From the same point of view, the inner surface of the closed end wall and the diaphragms 3a and 3b are preferably configured to be orthogonal to the axial direction of the tube portion 1. This is the same as in the case of the first embodiment.

  Next, the air chambers 4a and 4b will be described. In the present embodiment, the internal space of the tube part 1 is partitioned into two air chambers 4a and 4b by the diaphragm 3b. Therefore, the air chambers 4 a and 4 b are arranged in series along the axis of the tube part 1. In the air chamber 4a, the diaphragms 3a and 3b are arranged on both sides. On the other hand, in the air chamber 4b, a diaphragm 3b is disposed on one side of the air chamber 4a, and a closed end wall is disposed on the other side.

  The operational effects of the acoustic transmission path of the present embodiment configured as described above will be described.

  In the acoustic transmission line of this embodiment, in the mechanical model shown in FIG. 2 described above, the diaphragms 3a and 3b are arranged at the positions of the adjacent mass points 1A and 1B, and the closed end wall is arranged at the position of 1C. Corresponds to the case. According to the graph of FIG. 2, the distance from 1A to 1C corresponds to ½ wavelength of the element vibration having a wave number of π / 2L. The element vibration with the wave number π / 2L becomes a node at the position 1A of the open end and also becomes a node at the position 1C of the closed end wall, so that the acoustic transmission path of the present embodiment has an element with the wave number π / 2L. Can resonate with vibration.

  On the other hand, as shown in the graph of FIG. 2, the element vibration of the wave number π / L can be a node only at the intermediate point (ie, the position of L / 2) of the arrangement interval L of the diaphragms 3a and 3b. . Therefore, in the acoustic transmission path of the present embodiment in which the closed end 8 is disposed at a position of 1C that matches the arrangement period of the diaphragm, the element vibration with the wave number π / L cannot be a standing wave.

  In general, when one end of an acoustic transmission path is an open end and the other end is a closed end, an element having a wave number π / L (wavelength 2L) when the total length of the acoustic transmission path is set to an integral multiple of L Vibration cannot be a standing wave. This is different from the case of the first embodiment in which both ends of the acoustic transmission path are open ends.

  Also in this embodiment, the same effect as the case of the first embodiment can be obtained.

  As described above, one of the important features of the acoustic transmission path according to the first and second embodiments is that the acoustic transmission path is configured in the form of an acoustic resonance tube, so that the element vibration of a specific wavelength can be prevented. It is possible to respond selectively.

Here, an element vibration having an angular frequency higher than the angular frequency given by the mathematical formula (7) cannot propagate, and an element vibration having a frequency higher than a predetermined frequency does not exist in principle. It is desirable that the acoustic transmission line according to the present invention does not respond to a high-frequency sound wave, but responds only to a low-frequency sound wave, such as a low-frequency resonance tube of a speaker system. Suitable for use. Furthermore, if the acoustic transmission path according to the present invention is used, it is possible to configure a small resonance tube type speaker having a reduced overall length based on a propagation velocity lower than the speed of sound in the atmosphere. Hereinafter, a speaker system will be described as an embodiment of the present invention.
(Third embodiment)
FIG. 4 is a cross-sectional view of the speaker system according to the third embodiment of the present invention. The speaker system of this embodiment has a configuration in which a driver unit is acoustically coupled to an acoustic transmission path similar to that of the first embodiment shown in FIG. Here, the basic configuration of the acoustic transmission path itself is the same as that of the acoustic transmission path of FIG. 1 except that a through hole for acoustically coupling the driver unit is provided in the side wall of the tube portion. . Therefore, in the following description, the same code | symbol is used about the same structure, and repeated description is abbreviate | omitted.

  As shown in FIG. 4, the speaker system 30 of the present embodiment includes a driver unit 20 that is acoustically coupled to the acoustic transmission path 10 so as not to divide the inside of the tube body portion 1 in the axial direction of the tube body portion. is doing. In particular, the driver unit 20 is acoustically coupled to the acoustic transmission path 10 in the middle of the arrangement of the mass element and the elastic element so as not to divide the arrangement of the diaphragm 3 as the mass element and the air chamber 4 as the elastic element. Has been.

  A through hole 11 for acoustically coupling the driver unit 20 to the acoustic transmission path is provided on the side wall of the tube portion 1 of the acoustic transmission path 10. In the present embodiment, an odd number of air chambers, specifically, three air chambers 4a, 4b, and 4c are arranged in series, and the through hole 11 is formed of the odd number of air chambers 4a, 4b, and 4c. Of these, the air chambers 4b arranged in the center are arranged to communicate with the outside world. In particular, it is desirable that the through hole 11 is disposed at the center portion along the axial direction of the tube body portion 1. As will be described later, the central portion along the axial direction of the tube portion 1 corresponds to the node position of the velocity amplitude of the standing wave in the tube portion 1, and the end portion of the tube portion 1 is stationary. Corresponds to the antinode position of the wave velocity amplitude.

  Further, in the acoustic transmission path 10, the movable range of each diaphragm 3 is desirably ± 1.0 mm or more in order to allow sufficient amplitude as an antinode of the velocity amplitude of the standing wave. However, a small movable range in comparison with the diaphragms 3a and 3d may be set for the inner diaphragms 3b and 3c that are not located at the antinode position of the velocity amplitude of the standing wave. Further, when the spring member of the edge member 7 or other elastic support means (not shown) for supporting each diaphragm 3 and the diaphragm 3 is converted into Vas (equivalent capacity), one of the adjacent air chambers 4 is provided. It is desirable that it is larger than the volume. That is, as the elastic element, the relatively high elasticity of the downsized air chamber 4 is dominant, and the effect of increasing the resonance frequency by the security sealing means such as the edge member 7 is suppressed to a small level. For proper operation as the resonance tube type speaker system 30, it is desirable that the Qms (mechanical Q value) of the vibration system including the diaphragm 3 and the hermetic sealing means is 3.0 or more.

  The driver unit 20 acoustically coupled to the acoustic transmission path 10 has an oscillating surface and is an electroacoustic exchanger that converts an input electrical signal into a corresponding acoustic output signal. That is, the driver unit 20 functions as a speaker driver. An output impedance of a drive amplifier (not shown) that drives the driver unit 20 is electrically connected to the driver unit 20. Specifically, the output impedance of the drive amplifier is connected to both ends of the driver coil. Note that the Qts (total Q value) of the driver unit 20 is desirably 0.5 or less.

  In the present embodiment, as shown in FIG. 4, the driver unit 20 is disposed on the side wall of the tubular body portion 1 so that the back surface thereof faces the through hole 11. As described above, the through hole 11 is disposed so as to communicate the air chamber 4b disposed in the center with the outside world. Therefore, the driver unit 20 facing the through hole 11 has an odd number of air chambers 4a, 4b. 4c is coupled to the air chamber 4b disposed at the center. In addition, the through hole 11 is arranged at the central portion along the axial direction of the tube portion 1, whereby the driver unit 20 can be coupled to the node position of the standing wave in the tube portion 1.

  In this embodiment, in order to arrange the driver unit 20 on the outside of the side wall of the tube body portion 1, for example, a support portion is provided on the tube body portion 1. The support part forms the driver container 12 by partitioning the space from the outside so as to cover the back side of the driver unit 20 while fixing the driver unit 20 to the outside of the side wall of the tube part 1.

  Moreover, the speaker system of this embodiment can be comprised so that it may have the sound-absorbing material 14 inside the tubular-body part 1 as shown in FIG. The sound absorbing material 14 is, for example, a fiber assembly such as natural fiber, chemical fiber, glass fiber, etc., and is held inside a cylindrically formed net body, while being supported by a support means (not shown), the central axis (hereinafter, (Referred to as “tube axis”).

  The effect of the speaker system 30 of this embodiment comprised as mentioned above is demonstrated.

  First, when an input electrical signal is input from the drive amplifier, the driver unit 20 is driven to emit an acoustic output signal, that is, a sound wave. The sound wave radiated from the back surface of the driver unit 20 is guided to the acoustic transmission path 10 through the through hole 11 and is enhanced by resonating as the element vibration described above.

  FIG. 6 is a diagram schematically showing the pressure amplitude of the standing wave in the tube portion 1 in the present embodiment shown in FIG. As shown by a solid line in FIG. 6, the pressure amplitude becomes an antinode near the center of the central air chamber 4 b and forms a standing wave at both ends of the tubular body portion 1. Here, the velocity amplitude of the standing wave becomes a node near the center of the central air chamber 4b and becomes an antinode at both ends of the tube portion 1 as shown by a dotted line in FIG. Therefore, the element vibration in the present embodiment corresponds to the element vibration of k = π / 3L shown in FIG. 2, and this also resonates with the sound wave having the full length of the air column at both ends. This is equivalent to In the embodiment of FIG. 4, a standing wave corresponding to the element vibration of k = π / L shown in FIG. 2 can also be established. This is because the air column at both ends has a total length of 3/2 wavelengths. This is equivalent to a state of resonating with a sound wave.

  However, in a general air column resonance tube, there is further resonance in harmonics such as 5/2 wavelength and 7/2 wavelength, which causes auditory discomfort. In the acoustic transmission path, a standing wave is not established at a frequency higher than the element vibration of k = π / L corresponding to Equation (7). Therefore, the speaker system 30 of the present embodiment shown in FIG. 4 has an advantage of not generating harsh resonance of higher order than resonance corresponding to 3/2 wavelength in the air column resonance tube.

  In the resonance tube type speaker system 30 according to the present embodiment, since the sound wave having a frequency higher than the element vibration of k = π / L does not have a propagation mode due to the element vibration, each air chamber 4 and each diaphragm The sound wave is transmitted at a normal speed while being attenuated. Therefore, the total acoustic length of the tube with respect to medium and high sounds radiated from the back surface of the driver unit 20 matches the mechanical total length of the tube. Therefore, in the resonance tube type speaker system 30 according to the present embodiment, the medium and high sounds radiated from the back surface of the driver unit 20 are emitted to the outside through an extremely short acoustic path, so that the conventional resonance tube type speaker system is used. The so-called “boom sound” due to repeated wall reflections in a long pipe as described above is not generated and is recognized as a pleasant indirect sound.

  Further, in the speaker system 30 of the present embodiment, as shown in FIG. 5, the mid-high sound emission is also reduced by arranging the sound absorbing material 14 near the tube axis. The medium and high sounds radiated from the back surface of the driver unit 20 are recognized and beneficial as pleasant indirect sounds when radiated from the end of the tubular body portion 1, while the tubular body portion is reflected by reflection on the inner wall of the tubular body portion 1. If a standing wave along the diameter direction of 1 is formed, it is recognized as harmful sound and harmful. In this respect, in the speaker system 30 of the present embodiment, the sound absorbing material 14 is concentratedly disposed at the axial position where the antinodes of the standing wave along the diameter direction of the tubular body portion 1 are located, thereby standing along the diameter direction. Effectively absorbs harmful medium and high tones that form waves, and is transparent to transmission along the axial direction of beneficial medium and high sounds by ensuring a large cross-sectional opening in the vicinity of the side wall of the tube portion 1. Can be secured.

  By the way, in the speaker system of this embodiment shown in FIG. 4, the driver unit 20 is acoustically coupled to the acoustic transmission path 10 so as not to divide the internal space of the tubular body 1 in the axial direction of the tubular body 1. Yes. This point will be described while comparing the speaker system of the present embodiment with the speaker system of the first comparative example shown in FIG.

  The speaker system of the first comparative example shown in FIG. 7 also has a driver unit 20 ′ acoustically coupled to the acoustic transmission line 10 shown in FIG. 1, but unlike the speaker system of this embodiment, the driver unit. The inside of the acoustic transmission path 10 is divided in the axial direction of the tube portion 1 by 20 ′.

  Specifically, the speaker system of the first comparative example shown in FIG. 7 is obtained by replacing the diaphragm 3b with a driver unit 20 ′ in the acoustic transmission path of FIG. The problem with the speaker system of the first comparative example is that acoustic vibrations with discontinuous amplitude or phase are radiated before and after the diaphragm of the driver unit 20 '(hereinafter referred to as "driver unit diaphragm"). It is.

  In general, the pressure of acoustic vibration radiated from the driver unit 20 'is opposite in phase between the front surface and the back surface of the driver unit diaphragm. That is, when one is positive, the other is negative. For this reason, the pressure distribution in the tube portion 1 of the acoustic vibration radiated from the driver unit 20 ′ is an antisymmetric distribution in which the polarity is reversed before and after the driver unit diaphragm as shown by the solid line in FIG. It becomes. Further, the speed distribution is a symmetric distribution that is not smoothly connected before and after the driver unit diaphragm as shown by the dotted line in FIG. On the other hand, the reflected wave that is reflected at both ends of the tubular body portion 1 and exists in the tubular body portion 1 has a continuous and smooth distribution over the entire length of the tubular body portion 1 as in the case shown in FIG. Become. Therefore, in the speaker system of the first comparative example, the radiated wave from the driver unit 20 ′ and the reflected wave in the tube part 1 cannot have a mutually reinforcing phase relationship. That is, unlike the speaker system of the present embodiment, the speaker system of the first comparative example in which the driver unit 20 'is arranged in the middle of the transmission path as shown in FIG. 7 is as shown in FIG. A standing wave whose resonance is the entire length of the tube cannot be established.

  The arrangement of the driver units similar to that of the first comparative example shown in FIG. 7 is an arrangement common to the band-pass speaker systems disclosed in Patent Documents 5, 6, and 7 described above. Therefore, the bandpass speaker systems disclosed in Patent Documents 5, 6 and 7 also only have Helmholtz resonance for each acoustic mass before and after the driver unit 20 ′, as shown in FIG. This is a technique different from the speaker system of the present embodiment shown in FIG. 4 in that a standing wave whose resonance target is the entire length of the tube portion 1 cannot be established.

  Further, in the speaker system of the present embodiment shown in FIG. 4, the driver unit is disposed outside the side wall of the tubular body portion 1. This point will be described while comparing the speaker system 30 of the present embodiment with the speaker system of the second comparative example shown in FIG.

  The speaker system of the second comparative example shown in FIG. 8 also has a driver unit 20 ′ acoustically coupled to the acoustic transmission line 10 shown in FIG. 1, but unlike the speaker system of this embodiment, the driver unit. Is not arranged outside the side wall of the tube part 1.

  Specifically, in the speaker system of the second comparative example, both ends of the tube portion 1 are open, a driver unit 20 ′ is provided at one end of the tube portion 1, and the other end of the tube portion 1. Is provided with a diaphragm 3d as a mass element.

  In other words, the speaker system of the second comparative example shown in FIG. 8 is obtained by replacing the diaphragm 3a with the driver unit 20 ′ in the acoustic transmission path of FIG. In the speaker system of the second comparative example, the driver unit 20 ′ is arranged at the end of the acoustic transmission path, so that the inside of the tube part 1 is not divided by the driver unit 20 ′, and the entire length of the tube part is resonated. The problem of the first comparative example that the target standing wave cannot be established can be avoided. However, the form of FIG. 8 has another problem that the termination condition of the tube part 1 changes depending on the characteristics of the driver unit, as compared with the present embodiment.

  For example, FIG. 8 shows the pressure amplitude of a standing wave that becomes an abdomen in the central air chamber 4b and becomes a node at both ends of the tubular body portion 1 as in the present embodiment shown in FIG. At this time, the velocity amplitude of the standing wave becomes a node in the central air chamber 4b and becomes an antinode at both ends of the tube portion 1 as in the case of the present embodiment. The resulting driver unit 20 'diaphragm must have a large amplitude as an antinode of velocity amplitude.

  However, since the driver unit 20 'is electrically connected to the output impedance of the amplifier that drives the driver unit 20', both ends of the voice coil of the driver unit 20 'are connected when the output impedance of the drive amplifier is low. Equivalently short-circuited and strong electromagnetic braking works, and the diaphragm of the driver unit 20 'cannot vibrate freely. That is, when the output impedance of the drive amplifier is low, the driver unit 20 ′ disposed at the end of the tube part 1 cannot be antinode of the speed amplitude, and therefore, the present embodiment shown in FIG. The standing wave which makes the full length of the tubular-body part 1 a half wavelength like in the case of (5) cannot be materialized. At this time, the driver unit 20 ′ arranged at the end of the tube body can be a node of velocity amplitude, so that the total length of the tube is ¼ wavelength as in the case of the air column resonance tube closed at one end. Waves can be established.

  On the other hand, when the output impedance of the drive amplifier is high, both ends of the voice coil of the driver unit 20 ′ are equivalently opened and electromagnetic braking does not work, and the diaphragm of the driver unit 20 ′ can vibrate freely. it can. That is, when the output impedance of the drive amplifier is high, the driver unit 20 ′ disposed at the end of the tubular body portion 1 can be an antinode of the speed amplitude. Therefore, a standing wave having a half wavelength of the entire length of the tubular body portion 1 as in the case of the present embodiment shown in FIG. 6 can be established. Further, when the output impedance of the drive amplifier is intermediate, the driver unit 20 ′ cannot be an antinode or node of the speed amplitude, and there is no clear resonance point. As described above, the operation and sound quality of the speaker system shown in FIG. 8 vary greatly depending on the type of drive amplifier to be combined.

  Therefore, in the case of the speaker system of the second comparative example shown in FIG. 8, the problem that a standing wave whose resonance target is the entire length of the tube body cannot be solved, but the types of drive amplifiers to be combined are limited. . Therefore, the speaker system of the present embodiment shown in FIG. 4 has the effect that the characteristics of the driver unit 20 do not affect the termination condition of the tube, and the quality as an acoustic product regardless of the type of drive amplifier to be combined. Is more preferable in that it can be maintained and guaranteed.

  Further, in the speaker system 30 of the present embodiment shown in FIG. 4, the driver unit 20 does not serve as one diaphragm in the acoustic transmission path 10. This point will be described while comparing the speaker system 30 of the present embodiment with the speaker systems of the first comparative example shown in FIG. 7 and the second comparative example shown in FIG.

  When the driver unit 20 ′ also serves as one diaphragm in the acoustic transmission path 10 as in the first comparative example and the second comparative example, in order to resonate the acoustic transmission path with low sound, the driver unit It is necessary to set a large 20 ′ diaphragm mass, and therefore the response characteristics on the high-pitched side of the driver unit are likely to deteriorate. On the other hand, in this embodiment, since the driver unit 20 does not serve as one diaphragm in the acoustic transmission path 10, the response characteristic on the high sound side of the driver unit 20 does not deteriorate.

For example, in the acoustic transmission line 10 shown in FIG. 1, the tube part 1 is a cylindrical tube having an inner diameter of 0.10 m, and diaphragms having an effective diameter of 0.064 m are arranged at intervals of 0.10 m, and Set each parameter value as follows. A: 0.00785 m ² L: 0.10 m S ₀ : 790 N / m κ: 141700 N / m ² ρ: 1.29 kg / m ³ . Note that here, a correction calculation value different from the above equations (10) and (11) is used.

At this time, in order to set the resonance frequency of the element vibration of the wavelength 6L (wave number π / 3L), which makes the overall length of the tube 0.30 m substantially ½ wavelength, to 80 Hz, for example, the mass m ₀ of the diaphragm is 5 g In order to obtain 60 Hz, 10 g is required as the mass m ₀ of the diaphragm. This is an extremely large mass compared to the case where the mass m ₀ of the driver plate having a typical nominal diameter of 0.08 m (effective diameter 0.064 m) capable of responding to a high frequency of 10 kHz or higher is about 2 g. It is extremely difficult for such a large mass diaphragm to respond well to a high frequency of 10 kHz or higher.

  Therefore, in the speaker system of this embodiment, the driver unit 20 does not serve as the diaphragm 3 of the acoustic transmission path 10 and the vibration system mass of the driver unit 20 can be set independently of the design of the acoustic transmission path 10. Is extremely advantageous in order to ensure good response characteristics of the driver unit over a wide frequency band.

As described above, in the speaker system 30 of the present embodiment, as described above, a plurality of diaphragms 3 having a relatively large mass m ₀ may vibrate simultaneously, so that the reaction may be large. is there. When the tube part 1 itself vibrates in the opposite direction to the diaphragm 3 due to the reaction of the movement of the diaphragm 3, energy is consumed for the movement that does not contribute to the acoustic radiation, so that the acoustic radiation efficiency decreases. .

  In this regard, in the speaker system 30 of the present embodiment shown in FIG. 4, the driver unit 20 is coupled to the air chamber 4b disposed in the center portion among the odd number of air chambers 4a, 4b, and 4c. The acoustic radiation efficiency is prevented from decreasing.

  That is, by connecting the driver unit 20 to the air chamber 4b disposed in the center among the odd number of air chambers, the acoustic transmission path 10 is configured symmetrically about the driver unit 20 as shown in FIG. Is done. 6 is utilized, the pair of diaphragms 3a and 3c at left and right symmetrical positions always move in opposite directions. Therefore, no reaction is induced in the tube part 1 itself, and a decrease in acoustic radiation efficiency can be prevented.

  Unlike the present embodiment, even if the driver unit 20 is not coupled to the air chamber 4b disposed in the center portion among the odd number of air chambers, the mass of the tube body portion 1 is increased. The tube part 1 can be made not to respond to the movement of the diaphragm 3. However, from the viewpoint of configuring a lightweight speaker system, it is desirable to employ a configuration in which the driver unit 20 is coupled to the air chamber 4b disposed in the center, as in the speaker system 30 of the present embodiment.

  In the speaker system 30 of the present embodiment shown in FIG. 4, three or more air chambers 4a to 4c are arranged in series. Therefore, since the air chamber 4b including the velocity amplitude node is separated from the other air chambers 4a and 4b, the position of the node becomes unclear beyond the separation wall composed of the partition walls 6a and 6b and the diaphragms 3b and 3c. There is nothing. Further, since the wave front of the backside radiated wave of the driver unit 20 is adjusted by the diaphragms 3b and 3c, the flatness of the standing wave is maintained well. Therefore, the speaker system 30 of the present embodiment shown in FIG. 4 is a more advantageous form in that the decrease in the resonance of the transmission path due to the backside radiation wave of the driver unit 20 is small.

  Further, as shown in FIG. 4, by coupling the driver unit 20 to the node position of the velocity amplitude, the driver unit 20 is used in a state where the amplitude is small and distortion is small, and strong sound is generated from the tube end that is the antinode of the velocity amplitude. A resonance amplification effect that obtains radiation can be obtained.

  Note that, as described above, in the acoustic transmission line 10 used in the present embodiment, a low propagation speed that is 1/3 or less of the sound speed in the atmosphere can be easily obtained. Can be easily constructed. For example, in the present embodiment, a 1/2 wavelength resonance tube having a total length of only 0.3 m and a resonance frequency of 60 Hz or 80 Hz can be configured. Since the total length of the air column resonance tube corresponding to a half wavelength resonating with a sound wave having a frequency of 60 Hz is 2.8 m, the total length of the speaker system 30 of the present embodiment is larger than that of a speaker system using a normal air column resonance tube. Has been greatly shortened.

  Here, the Example performed in order to confirm the effect of the speaker system 30 of this embodiment is shown. The tube portion 1 is a cylindrical tube having an inner diameter of 0.09 m, and the lengths of the air chambers 4a, 4b, and 4c are all 0.11 m. The effective diameter of each diaphragm was 0.064 m. The masses of the diaphragms 3a and 3d arranged at the end of the tube part 1 were 16 g, and the masses of the diaphragms 3b and 3c arranged inside the tube part 1 were 20 g. The spring constant of the edge member 7 was S0 = 790 N / m in common for all the diaphragms 3a, 3b, 3c. When this spring constant is converted to Vas (equivalent capacity), it is about 1.9 liters, which is larger than the volume of the adjacent air chamber 4 being about 0.7 liters. Therefore, the relatively high elasticity of the downsized air chamber 4 is dominant as the elastic element, and as a result, the effect of increasing the resonance frequency by the edge member 7 and the like is suppressed to a small level.

  In this embodiment, the movable range of all the diaphragms 3a, 3b, and 3c was ± 2.5 mm, and a large value was secured as a diaphragm having an effective diameter of 0.064 m. This has the effect that the diaphragms 3a and 3d arranged at the end portions can be amplified with a margin as antinodes of standing waves. The inner diaphragms 3b and 3c may have a small movable range in comparison with the diaphragms 3a and 3d.

  The Qms of the vibration system composed of the diaphragm 3 and the edge member 7 was set to 5.2. If Qms is too small, the transmission loss of element vibration in the tube increases and the resonance decreases. For proper operation as a resonance tube type speaker system, it is desirable that Qms is 3.0 or more. This is not the case when configuring a transmission line type speaker system to be described later that does not actively use resonance.

  The driver unit 20 has an effective diameter of 0.064 m, fs = 110 Hz, and Qts = 0.33. When the volume of the air chamber 4 is as small as 1 liter or less as in this embodiment, it is important to select a driver unit 20 having a small Qts. Desirably, by using a driver unit having a Qts of 0.5 or less, a flat frequency response that suppresses the sharpness of resonance and has a flat frequency response at a frequency near the resonance point formed by the vibration system of the driver unit 20 and the air chamber 4 behind. Characteristics can be obtained. In addition, since the driver unit 20 having a small Qts maintains responsiveness to a frequency region lower than the resonance point, it forms a relatively strong coupling with the resonance of the acoustic transmission line 10 set to a frequency lower than the resonance point. It has the advantage of being possible.

  When correction is made in consideration of the fact that the effective vibration area of each diaphragm 3 is 51% of the cross-sectional area in the tube, the above equations (10) and (11) assuming an infinite system are the shortest wavelength 2L ( The frequency of element vibration at a wave number π / L is calculated to be 120 Hz, and the phase velocity Vp is calculated to be 26 m / s, which is reduced to about 8% of the speed of sound in the air. Similarly, at a wavelength of 6 L (wave number π / 3 L), the frequency of element vibration is calculated as 60 Hz, and the phase velocity Vp is calculated as 40 m / s. In contrast, in an actual system composed of a finite number of mass elements, resonance was observed at 107 Hz and 46 Hz from impedance measurement. At the same time, antiresonance was observed at 120 Hz.

  In the present embodiment, it is possible to configure an acoustic transmission path corresponding to a half wavelength at a frequency of 46 Hz with a total length of only 0.33 m. Since the total length of the air column resonance tube corresponding to ½ wavelength that resonates with a sound wave having a frequency of 46 Hz is about 3.6 m, it can be significantly shortened. In addition, an ordinary air column resonance tube resonates at a plurality of frequencies corresponding to the fundamental resonance frequency and its harmonics, whereas in this embodiment, only a harmonic resonance of 107 Hz exists. Yes.

(Fourth embodiment)
FIG. 9 is a cross-sectional view of a speaker system according to a fourth embodiment of the present invention. The present embodiment is the same as the structure of the speaker system of the third embodiment shown in FIG. 4 except that the diaphragm 3 is configured to transmit medium and high tones more effectively. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  The diaphragm 3a of the present embodiment includes the diaphragm 15 and an annular reinforcing frame 16 that reinforces the peripheral edge of the diaphragm 15. The vibration film 15 is a thin paper thin film, and its peripheral portion, that is, the outer periphery is reinforced by an annular reinforcing frame 16. The reinforcing frame 16 is elastically supported on the inner surface of the tube portion 1 by an edge member 7 which is an airtight sealing means. The vibration film 15 may be a film, a resin, a metal foil, or a composite thereof formed at least partially thinner than a paper film. The reinforcement frame 16 can be made of a light metal such as aluminum or a high-strength resin material such as a fiber reinforced resin. The reinforcing frame 16 may have a lattice-shaped or radial reinforcing bar (not shown) added to the inside thereof. Further, a plate spring-like elastic support means may be added to the rear end of the reinforcing frame 16 to elastically support the axial motion while restraining the radial motion. Although the diaphragm 3a has been described as described above, the other diaphragms 3b, 3c, and 3d have the same configuration.

  The speaker system 30 configured as described above has the following operational effects in addition to the operational effects similar to those of the speaker system of the third embodiment.

  Since the mass necessary for the operation of the acoustic transmission path 10 is concentrated on the reinforcing frame 16 and the outer periphery of the vibrating membrane 15 is reinforced by the reinforcing frame 16, the vibrating membrane 10 is maintained while maintaining the strength necessary for large amplitude operation. It is possible to set the thickness of the thin film. For this reason, medium and high tones of small amplitude are efficiently transmitted by deformation vibration (curvature deformation, split vibration) of the diaphragm 15 having a small mass, and low sound of large amplitude is transmitted from the diaphragm that is the entire mass element including the reinforcing frame 16. It can be transmitted by reciprocating motion.

(Fifth embodiment)
The speaker system of this embodiment is a speaker system of the third embodiment shown in FIG. 4 in which parameters including the distance between diaphragms giving the length of the air chamber and the mass of the diaphragm are changed. In the speaker system according to the third embodiment, a large peak and dip may occur in the frequency characteristics due to strong resonance and anti-resonance. Therefore, in the present embodiment, the parameters are changed for the purpose of weakening too strong resonance and anti-resonance. The basic configuration of the speaker system of this embodiment is the same as that of the speaker system of the third embodiment shown in FIG. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  In the speaker system of the present embodiment, among the air chambers 4a, 4b, and 4c arranged in series, the length of the air chamber 4b disposed at the center is the length of the air chambers 4a and 4c disposed at the end. It is longer than that. Here, in order to expand the reproduction band in the low frequency direction and weaken strong resonance and anti-resonance to suppress the peak and dip, the center along the axis of the tube portion 1, that is, the air chamber 4b is used as a reference. It is desirable that the lengths of the air chamber 4a and the air chamber 4c at the symmetric positions are equal, and the change in the air chamber length is symmetrical. In other words, the air chambers 4a and 4c that are in a symmetrical position with respect to the air chambers 4b arranged in the center of the tube body portion 1 are arranged on the end side of the tube body portion 1 with the same capacity. Therefore, the volume of the air chamber is changed symmetrically so that the volume of the air chamber is reduced.

  However, also in this case, from the viewpoint of maintaining the propagation mode of the element vibration as shown in the schematic diagram shown in FIG. 2, for example, the length in an arbitrary air chamber length (interval between adjacent diaphragms) It is desirable that the thickness ratio does not exceed 1.5.

  Moreover, at least one mass element 3c among the diaphragms 3 which are a plurality of mass elements is lighter than the other diaphragms 3a, 3c and 3d. In the present embodiment, the masses of the diaphragms at symmetrical positions with the driver unit 20 as the center are different. Specifically, the masses are different between the diaphragms 3a and 3d at the symmetrical positions, and the mass is different between the diaphragms 3b and 3c at the target positions. In particular, in the present embodiment, in order to keep the strength of the standing wave whose resonance target is the entire length of the tubular body 1 while flattening the frequency characteristics, it is more than the average mass of all the diaphragms 3a, 3b, 3c, 3d. The diaphragms 3a and 3c having a small mass and the diaphragms 3b and 3d having a mass larger than the average mass of all the diaphragms 3a, 3b, 3c and 3d are alternately arranged. However, also in this case, from the standpoint of maintaining the propagation of the element vibration as shown in the schematic diagram shown in FIG. 2, that is, the resonance, the diaphragm 3a, which is an arbitrary mass element excluding the element vibration driver unit 20, It is desirable for the mass ratio between 3b, 3c, 3d not to exceed 3, more advantageously not to exceed 2.

  Even when the S / m (S is a spring constant, m is mass) and the distance L between adjacent mass points are non-uniform in the acoustic transmission path 10 as described above, By using the average value of each S / m and the average value of each L, the speaker system of the present invention can be designed within a practically adjustable range although there is an error.

  Also, when using the formula (11) that takes into account parasitic elements, the speaker system of the present invention can be designed within a practically adjustable range by replacing the contents of the square root and L with their respective average values. it can.

  According to the speaker system of the present embodiment configured as described above, even when the tubular body portion 1 has a short physical total length, it is strong while maintaining the same bass enhancement effect as the long full-length tubular body portion. By weakening the resonance and anti-resonance, significant peaks and dips can be suppressed, and the flatness in frequency characteristics can be improved.

  Here, the Example performed in order to confirm the effect of the speaker system 30 of this embodiment is shown. The length of the air chambers 4a and 4c is shortened to 0.1 m while the total length of the tube part 1 is kept the same as in the case of the example in the third embodiment, and the length of the air chamber 4b is 0.13 m. Extended. Thus, by changing the length of the air chamber 4 and shifting the resonance point corresponding to the wave number π / L in each air chamber 4, the resonance corresponding to the wave number π / L of the entire tube portion 1 can be weakened. it can. A standing wave equivalent to a wave number π / 3L having a full length of the tube portion 1 of ½ wavelength is insensitive to changes on a short distance scale, and in this embodiment, the change in the air chamber length is symmetric. Therefore, the influence on the standing wave corresponding to the wave number π / 3L is small. In the present embodiment, the resonance point formed by the driver unit and the air chamber 4b is slightly moved to the lower frequency side by extending the length of the air chamber 4b while maintaining the entire length of the tube portion 1. Yes. This acts in the direction of strengthening the coupling between the tube resonance and the driver unit existing in the frequency range lower than the reproduction band of the driver unit and expanding the reproduction band to the low frequency side.

  In this example, the masses of the diaphragms 3a and 3b are maintained at 16 g and 20 g, respectively, as in the example of the third embodiment, while the mass of the diaphragm 3c is 10 g and the mass of the diaphragm 3d is the same. Changed to 20 g, respectively. As a result, the masses of the diaphragms 3a, 3b, 3c, and 3d are 16 g, 20 g, 10 g, and 20 g, respectively, and the diaphragm having a mass smaller than the average mass of 16.5 g and the average mass of 16.5 g are larger. The diaphragm having the mass is alternately arranged. As a result, since the resonance frequency of the vibration element including the diaphragms 3a and 3c is shifted to the high frequency side, it cancels out the anti-resonance observed in the first embodiment, and the dip of the frequency characteristic near the anti-resonance point can be reduced. it can. Further, the asymmetry of the mass distribution of the entire system is increased, and the peak of the frequency characteristic due to the standing wave corresponding to the wave number π / 3L is reduced, so that the frequency characteristic is flattened as a whole together with the reduction of the dip. The light mass diaphragms 3a and 3c and the heavy mass diaphragms 3b and 3d are alternately arranged to prevent the standing wave whose resonance target is the entire length of the tubular body 1 from being extremely suppressed. Therefore, the frequency characteristic is flattened without reducing the reproduction band on the low frequency side. On the other hand, a light-mass diaphragm is concentrated on one side (for example, the air chamber 4a side) of the tube portion 1, and a heavy-mass diaphragm is disposed on the other side (for example, the air chamber 4c side) of the tube portion 1. Is concentrated, the tube part 1 is substantially divided into two parts due to the uneven distribution of the mass, and the strength of the standing wave whose resonance target is the entire length of the tube part 1 is significantly weakened, so the reproduction band on the low frequency side is reduced. .

  The Qms of the vibration system composed of the diaphragm 3 and the edge member 7 was 3.7.

  By changing the parameters as described above, in this embodiment, the reproduction band is expanded in the low frequency direction, peaks and dips are suppressed, and the flatness in frequency characteristics is improved.

  As described above, in the fifth embodiment, the case where the resonance is suppressed by changing the parameter has been described. However, the resonance can be suppressed for the purpose of adjusting the sound quality also by other modes. The following sixth and seventh embodiments show other examples of suppressing resonance for the purpose of sound quality adjustment.

(Sixth embodiment)
FIG. 10 is a cross-sectional view of a speaker system according to a sixth embodiment of the present invention. The speaker system of the present embodiment is configured such that the tube axis of the tube portion 1 is shifted in the middle thereof. In other words, the tube part 1 has a plurality of portions whose axes are shifted from each other. In FIG. 10, the tube axis is shifted between the portion of the tubular body portion 1 forming the air chamber 4a and the portion of the tubular body portion 1 forming the air chamber 4c. In accordance with such displacement of the tube axis, the first group of diaphragms composed of diaphragms 3a and 3b and the second group of diaphragms composed of diaphragms 3c and 3d are mutually radial (perpendicular to the vibration direction). Direction) deviation.

  Resonance can be suppressed for the purpose of sound quality adjustment by shifting the tube axis of the tube portion 1 instead of the parameter change as described in the fifth embodiment or together with the parameter change.

(Seventh embodiment)
FIG. 11 is a cross-sectional view of a speaker system according to a seventh embodiment of the present invention. The speaker system of the present embodiment is configured such that the tube axis of the tube portion 1 is bent in the middle thereof. That is, the tube part 1 is bent at at least one place. In FIG. 11, the tube axis is bent between the portion of the tube portion 1 forming the air chamber 4a and the portion of the tube portion 1 forming the air chamber 4c. According to such bending of the tube axis, the first group of diaphragms composed of the diaphragms 3a and 3b and the second group of diaphragms composed of the diaphragms 3c and 3d are not parallel to each other, and have a predetermined angle. Have.

  As described in the fifth embodiment, the resonance can be suppressed for the purpose of adjusting the sound quality by bending the tube axis of the tube body portion 1 instead of or together with the parameter change.

(Eighth embodiment)
In said 1st-7th embodiment, the case where a diaphragm was used as a mass element was demonstrated. From the viewpoint of miniaturization of the speaker system and from the viewpoint of preventing reduction in radiation efficiency and generation of unnecessary noise, it is desirable to use a diaphragm as a mass element, but as in this embodiment, as a mass element, A port tube communicating between the air chambers can also be used.

  FIG. 12 is a cross-sectional view of a speaker system according to an eighth embodiment of the present invention.

  The speaker system of this embodiment is the same as the speaker system of the third embodiment shown in FIG. 4 except that a port tube is used instead of a diaphragm as a mass element that partitions adjacent air chambers. It is the same. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  The speaker system 30 of this embodiment also includes the acoustic transmission path 10 and the driver unit 20. As shown in FIG. 12, in the acoustic transmission path 10 of the speaker system 30 of the present embodiment, a port tube 13a is used as a mass element that partitions between the adjacent air chambers 4a and 4b, instead of the diaphragm 3b. The port pipe 13b is used instead of the diaphragm 3c as a mass element that partitions between the adjacent air chamber 4b and the air chamber 4c. On the other hand, diaphragms 3a and 3b are provided at both ends of the tube portion 1 as mass elements, as in the case of the third embodiment.

  Partition walls 6 a and 6 b are provided on the inner surface of the tube portion 1. The internal space of the tube part 1 is partitioned into air chambers 4a, 4b, and 4c by the partition walls 6a and 6b. The partition walls 6a and 6b partition the air chambers 4a, 4b, and 4c and support the port pipes 13a and 13b, respectively. The port pipe 13a communicates between the adjacent air chambers 4a and 4b, and the port pipe 13b communicates between the adjacent air chambers 4b and 4c.

  The diaphragms 3a and 3b not only function as mass elements, but the air in the port tubes 13a and 13b also functions as mass elements. Arranged in the order of the diaphragm 3a, the air chamber 4a, the port tube 13a, the air chamber 4b, the port tube 13b, the air chamber 4b, and the diaphragm 3b along the axial direction of the tube body inside the tube body 1. Therefore, also in the acoustic transmission path 10 of the present embodiment, the mass elements and the elastic elements are alternately and periodically arranged along the axial direction of the tube portion 1. The axis lines of the port pipes 13 a and 13 b are parallel to the axis line of the tube body portion 1. In other words, the air in the port pipes 13a and 13b, which are mass elements, vibrates along the shaft boat of the pipe body section 1.

  The driver unit 20 is acoustically coupled to the acoustic transmission path 10 configured as described above. As in the case of the third embodiment, the driver unit 20 is acoustically coupled to the acoustic transmission path 10 so as not to divide the interior of the acoustic transmission path 10 in the axial direction of the tubular body portion 1. Specifically, the through hole 11 is arranged on the side wall of the tube portion 1 so that the air chamber 4b arranged at the center of the odd number of air chambers 4a, 4b, and 4c communicates with the outside. The driver unit 20 is arranged outside the side wall of the tubular body portion 1 in accordance with the position of the through hole 11. As in the case of the third embodiment, the through-hole 11 is arranged at the central portion along the axial direction of the tube portion 1, so that the driver unit 20 is fixed in the tube portion 1. It is desirable to couple to the wave node position.

  The speaker system 30 configured as described above has substantially the same operational effects as the speaker system of the third embodiment.

  Note that the speaker system 30 of the present embodiment uses the port tubes 13a and 13b as mass elements, but the port tubes 13a and 13b occupy a larger volume than the diaphragm, so that the speaker system 30 can be downsized. From the viewpoint, it can be said that the speaker system of the third embodiment is more advantageous. Further, if the diameters of the port tubes 13a and 13b are set small in order to reduce the volume of the port tubes 13a and 13b while maintaining the resonance frequency of the mass element, the acoustic radiation efficiency is lowered and the port tubes 13a and 13b are reduced. Wind noise generated by the air flow passing through the air may become prominent. Further, the port tubes 13a and 13b resonate as independent air column resonance tubes, particularly in the middle and high sound range that is unpleasant in hearing. These points are also disadvantageous compared to the diaphragm. The reduction in radiation efficiency and the generation of unnecessary noise are particularly serious auditory problems when the port tube is arranged exposed at the end of the tube portion 1. Therefore, even when the port tubes 13a and 13b are used, it is desirable that the mass elements arranged at the end portions of the tube portion 1 are the diaphragms 3a and 3b as in the present embodiment.

  As described above, it is desirable to use a diaphragm as a mass element from the viewpoint of miniaturization of the speaker system and prevention of reduction of radiation efficiency and generation of unnecessary noise. As in the embodiment, by adopting the simple structure of the port tubes 13a and 13b as mass elements, a low propagation speed of 1/3 or less of the sound speed in the atmosphere can be obtained, and the resonance frequency is 100Hz or less. Since the half-wavelength resonance tube having a tube total length of 0.5 m or less can be easily configured, the overall length of the speaker system of this embodiment is significantly larger than that of a speaker system using a normal air column resonance tube. Shortened.

(Ninth embodiment)
In said 1st-8th embodiment, the case where the several air chamber was arranged in series was demonstrated. Certainly, from the viewpoint of preventing mass concentration per diaphragm functioning as a mass element, it is desirable that a plurality of air chambers be arranged in series, but as in this embodiment, Even when there is only one air chamber, it is possible to configure a speaker system using resonance of element vibration in which the total length of the tube portion is ½ wavelength.

  FIG. 13 is a cross-sectional view of the speaker system according to the ninth embodiment of the present invention. In the speaker system according to the present embodiment, the number of diaphragms is reduced to two by removing two diaphragms located at the center of the four diaphragms in the speaker system according to the third embodiment. Corresponding to things. Therefore, the entire internal space of the tube part 1 is a single air chamber. Except for these points, the speaker system of this embodiment is the same as that of the speaker system of the third embodiment shown in FIG. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  The speaker system 30 of this embodiment includes an acoustic transmission path 10 and a driver unit 20. As shown in FIG. 13, the acoustic transmission path 10 of the present embodiment also has a tube portion 1 whose both ends are open ends, as in the case of the third embodiment.

  At both ends of the tube part 1, diaphragms 3a and 3b are provided as mass elements, respectively. Further, the internal space of the tubular body portion 1 is partitioned from the outside by the diaphragms 3 a and 3 b to form one air chamber 4. Since the diaphragms 3a and 3b each function as a mass element and the air chamber 4 functions as an elastic element, the acoustic vibration unit 10 of the present embodiment is also in the axial direction of the tube unit 1 inside the tube unit 1. It can be said that the mass elements and the elastic elements are arranged alternately and periodically along.

  A through hole 11 for acoustically coupling the driver unit 20 to the acoustic transmission path 10 is provided in the central portion of the side wall of the tubular body portion 1. The driver unit 20 is disposed outside the side wall of the tubular body portion 1 so that the back surface thereof faces the through hole 11, and is acoustically connected to the acoustic transmission path 10 at the center of the air chamber 4 through the through hole 11. Is bound to.

  Here, it is desirable that the diameter of the through hole 11 is 1/3 or less of the entire length of the tubular body portion 1. In particular, as in the present embodiment, the central portion of the tube portion 1 that becomes a node of the velocity amplitude of the standing wave and the end portion of the tube portion 1 that becomes the antinode of the velocity amplitude of the standing wave are diaphragms or the like. In the structure that is not separated by the above, the node position of the standing wave becomes unclear due to the superposition of the back radiation and the standing wave of the driver unit 20, and at the same time the planarity of the standing wave is lowered. Therefore, it is desirable to make the node position of the standing wave clear and improve the planarity of the standing wave by making the diameter of the through hole 11 equal to or less than 1/3 of the total length of the tube part 1. As in the case of the third embodiment, the through-hole 11 is arranged at the central portion along the axial direction of the tube portion 1, so that the driver unit 20 is fixed in the tube portion 1. It is desirable to couple to the wave node position.

  Further, as shown in FIG. 13, the sound absorption in the case of the third embodiment is provided in the vicinity of the central portion along the axial direction of the tubular body portion 1 that is the installation position of the driver unit 20 and is also the node position of the velocity amplitude. The sound absorbing material made of the same material as the material 14 is intensively arranged. The sound absorbing material 14 is, for example, a fiber aggregate such as natural fiber, chemical fiber, glass fiber, etc., and is disposed in the vicinity of the tube axis by a supporting means (not shown) while being held inside a cylindrically formed net. .

  The speaker system 30 configured as described above has substantially the same operational effects as the speaker system of the third embodiment.

  In addition, when the diameter of the through hole 11 is 1/3 or less of the entire length of the tubular body portion 1, the node position of the standing wave can be clarified and the planarity of the standing wave can be improved.

  Further, the sound absorbing material 14 intensively arranged in the vicinity of the node position has substantially no sound absorbing effect on low-frequency sound waves having a small velocity amplitude in the vicinity of the node position, while radiating from the back surface of the driver unit 20. The generated mid-high sound wave efficiently absorbs sound. In FIG. 13, this selective sound absorption effect can reduce the emission of medium and high sounds from the back surface of the driver unit 20 without hindering the resonance of the transmission path in the low sound.

  As described above, the mid-high sound radiated from the back surface of the driver unit 20 is recognized and beneficial as a pleasant indirect sound when radiated from the end portion of the tubular body portion 1, while it is beneficial in the tubular wall of the tubular body portion 1. If a standing wave along the diameter direction of the tube part 1 is formed by reflection, it is recognized as harmful sound and harmful. In this regard, also in the speaker system of the present embodiment, the standing wave along the diameter direction is formed by intensively arranging the sound absorbing material 14 at the axial position where the antinode of the standing wave along the diameter direction of the tube portion 1 is located. By effectively absorbing the harmful mid-high sounds that form the sound, while ensuring a large cross-sectional opening in the vicinity of the side wall of the tubular body portion 1, it is possible to transmit the transmission along the axial direction of beneficial mid-high sounds. Can be secured.

  In the speaker system 30 of the present embodiment, an air chamber including a velocity amplitude node is not separated from other air chambers, but includes a velocity amplitude node as compared with the speaker system 30 of the present embodiment. The speaker system of the third embodiment in which the air chamber is separated from other air chambers is advantageous in that the decrease in resonance of the transmission path due to the backside radiation wave of the driver unit 20 is small. That is, when an air chamber including a velocity amplitude node is separated from other air chambers as in the speaker system of the third embodiment, the node position does not become unclear. Further, since the wave front of the backside radiated wave of the driver unit 20 is flattened by the diaphragm inside the tubular body portion 1, the planarity of the standing wave is maintained well.

  Furthermore, in the present embodiment consisting of a single air chamber 4, the region corresponding to the antinode of the standing wave and the region corresponding to the node coexist in the vicinity of the same air chamber. It is difficult to maintain a clear amplitude difference from the region corresponding to the node, and therefore the resonance intensity is relatively weak. On the other hand, when the air chamber including the velocity amplitude node is separated from the other air chambers as in the speaker system of the third embodiment, the amplitude difference between the belly and the node is ensured and strong resonance is established. It is more advantageous in that it is possible.

Note that resonance of element vibration in which the total length of the tube portion 1 is ½ wavelength can also be used in the speaker system 30 of this embodiment in which the number of diaphragms is reduced to two. For example, in FIG. 13, the tube portion 1 is a cylindrical tube having an inner diameter of 0.10 m, and diaphragms having an effective diameter of 0.064 m are arranged at intervals of 0.10 m, and each parameter value is set as follows: Set as follows. A: 0.00785 m ² L: 0.30 m S ₀ : 790 N / m κ: 141700 N / m ² ρ: 1.29 kg / m ³ . Note that here, a correction calculation value different from the above formulas (10) and (11) is used, and L is the distance between the diaphragms, that is, the total length of the tube portion 1.

At this time, 10 g is required as the mass m ₀ of the diaphragm in order to set the resonance frequency of the element vibration of the wavelength 2L (wave number π / 3L) having a half wavelength of 0.30 m of the entire length of the tube to, for example, 80 Hz. In order to obtain 60 Hz, 18 g is required as the mass m ₀ of the diaphragm.

On the other hand, in the case of the speaker system according to the third embodiment in which four diaphragms are arranged on the entire length of the same 0.30 m tubular body portion 1 and element vibration with a wavelength of 6L (wave number π / 3L) is used, As described in the first embodiment, in order to set the resonance frequency to 80 Hz, 5 g is required as the mass m ₀ of the diaphragm, and in order to set the resonance frequency to 60 Hz, 10 g is required as the mass m ₀ of the diaphragm. . Note that L is a distance between the diaphragms, that is, 1/3 of the total length of the tubular body portion 1.

  Comparing this result, even with the speaker system of this embodiment, it is possible to easily construct a 1/2 wavelength resonance tube having a resonance frequency of 100 Hz or less and a total length of the tube portion 1 of 0.5 m or less. Although the overall length of the speaker system of the present embodiment can be significantly shortened compared to a speaker system using a normal air column resonance tube, the mass of each diaphragm 3 can be increased by reducing the number of diaphragms 3. Can be seen to concentrate. As described above, if the mass of the diaphragm 3 is excessive, the transient response characteristic is deteriorated. In particular, the form of FIG. 13 in which the mass concentrates on the diaphragms 3a and 3b provided at the ends of the tube part 1 where the acceleration is maximum is disadvantageous compared to the case of the third embodiment. If the mass of the diaphragm 3 is excessive, the life of the vibration support system such as the edge member 7 or the damper is reduced.

  Therefore, it is clear that the speaker system according to the third embodiment is more desirable than the speaker system according to the present embodiment from the viewpoint of deterioration of the transient response characteristics and deterioration of the life of the vibration support system. Depending on conditions such as durability required for a product, a structure in which the number of mass elements and air chambers is reduced may be employed as in this embodiment.

(Tenth embodiment)
FIG. 14 is a cross-sectional view of the speaker system according to the tenth embodiment of the present invention. In the speaker systems of the third to ninth embodiments described above, the driver unit is disposed outside the side wall of the tube body portion, and the driver unit and the acoustic transmission path 10 are directly connected via the through hole. Explained the case of linking.

  On the other hand, the speaker system of the present embodiment has a port tube that connects the driver unit and the inside of the tube body, and the acoustic coupling method between the driver unit and the acoustic transmission path is different. Except for this point, the speaker system of this embodiment has the same configuration as the speaker system of the third embodiment shown in FIG. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  As shown in FIG. 14, in the speaker system 30 of the present embodiment, the driver unit 20 is acoustically coupled to the acoustic transmission path 10 via the port pipe 18. Specifically, the port pipe 18 functions as a coupling pipe that couples the driver unit 20 and the inside of the tubular body portion 1. The port tube 18 may be formed of a flexible material that can be bent.

  In the example shown in FIG. 14, the driver container 12 is provided so as to cover the back side of the driver unit 20, and the driver container 12 is a cabinet independent of the acoustic transmission path 10. One end of the port pipe 18 communicates with the driver container 12. The other end of the port pipe 18 communicates with the air chamber 4b located at the center of the three air chambers 4a, 4b, 4c arranged in series. As a result, also in the speaker system 30 of the present embodiment, the driver unit 20 is coupled to the air chamber 4b where the node of the velocity amplitude of the standing wave is located.

  The speaker system 30 of the present embodiment configured as described above has not only the same operational effects as the speaker system of the third embodiment, but also the following operational effects. The port tube 18 performs Helmholtz resonance at a predetermined frequency, and an acoustic signal enhanced at this frequency is injected into the acoustoelectric transmission line 10. In the speaker system 30 of the present embodiment, the driver unit 20 can be arranged independently of the tube body portion 1, so that the driver unit 20 is not restricted by the shape and dimensions of the tube body portion 1. Therefore, the driver container 12 having a relatively large capacity can be used, and there is an advantage that a driver unit having a relatively high Qts can be selected.

  Here, the Example performed in order to confirm the effect of the speaker system 30 of this embodiment is shown.

  A driver vessel 12 having an inner volume of 4.0 liters is coupled to a transmission line having the same configuration as that of the above-described example in the third embodiment via a bendable port pipe 18 having an inner diameter of 2 cm and a total length of 70 cm. The port tube 18 resonates at Helmholtz at 46 Hz and injects an acoustic signal enhanced at this frequency into the transmission line. In the present embodiment, it is possible to use a large-capacity driver container 12 without being restricted by the shape and size of the tube state 1, and thus a driver unit having a relatively high Qts can be selected. In the present embodiment, the peak of the frequency characteristic in the vicinity of the resonance point by the driver unit 20 and the driver container 12 is suppressed while using a driver unit with an effective diameter of 0.064 m, fs = 100 Hz, and Qts = 0.6. Yes.

(Eleventh embodiment)
FIG. 15 is a cross-sectional view of the speaker system of the eleventh embodiment. In the speaker system according to the third embodiment, the case where an odd number of air chambers are arranged in series has been described.

  On the other hand, in the speaker system of the present embodiment, an even number of air chambers are arranged in series, and a driver is provided in at least one of the two air chambers arranged in the center of the even number of air chambers. Units are acoustically coupled. Except for this point, the speaker system of this embodiment has the same configuration as the speaker system of the third embodiment shown in FIG. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  As shown in FIG. 15, in the speaker system 30 of the present embodiment, an even number of air chambers, specifically, four air chambers 4a, 4b, 4c, and 4d are arranged in series. The through hole 11 is provided in at least one of the plurality of air chambers 4a, 4b, 4c, and 4d arranged in the center (the air chamber 4b in FIG. 15). It has been. Therefore, the driver unit 20 is acoustically coupled to the two air chambers 4b, 4c arranged in the center of the plurality of air chambers 4a, 4b, 4c, 4d. In other words, the driver unit 20 is acoustically connected to at least one of the air chambers 4b and 4c adjacent to the diaphragm 3c disposed in the center among the plurality of diaphragms 3a, 3b, 3c, 3d, and 3e that are mass elements. It can be said that they are combined.

  The speaker system 30 of the present embodiment configured as described above has substantially the same operational effects as the speaker system of the third embodiment.

  As described in the third embodiment, the driver unit 20 is coupled to the node position of the velocity amplitude, so that the driver unit 20 can be used in a state where the amplitude is small and distortion is small. A resonance amplification effect that obtains strong acoustic radiation from a certain tube end can be obtained. In this case, in the tubular body portion 1 divided into an even number of air chambers 4a, 4b, 4c, and 4d as in the present embodiment, when using the resonance of element vibration with the full length of the tube being ½ wavelength, The node position of the velocity amplitude of the standing wave corresponds to the central diaphragm 3 c and does not correspond to the air chamber 4. However, like the speaker system 30 of the present embodiment, the driver unit 20 is coupled to the air chamber 3b adjacent to the diaphragm 3c, thereby obtaining a resonance amplification effect similar to that of the speaker system of the third embodiment. be able to.

(Twelfth embodiment)
FIG. 16 is a sectional view of a speaker system according to a twelfth embodiment of the present invention. In the speaker systems according to the third to eleventh embodiments, the case where both ends of the tube body are open has been described.

  On the other hand, in the speaker system of the present embodiment, one end of the tube body part is closed by the closed end wall surface. The driver unit 20 is not acoustically coupled to the central air chamber, but is acoustically coupled to the air chamber adjacent to the closed end wall surface. Except for these points, the speaker system of this embodiment has the same configuration as the speaker system of the third embodiment shown in FIG. Therefore, the same reference numerals are used for the same configurations as those of the speaker system of the third embodiment, and repeated description is omitted.

  As shown in FIG. 16, in the speaker system 30 of the present embodiment, one end of the tube part 1 is closed. In other words, one end is a closed end. Therefore, a closed end wall 8 is provided at one end of the tubular body portion 1. On the other hand, the other end of the tube part 1 is open, in other words, an open end. A diaphragm 3a is disposed at the other end of the tubular body 1.

  In addition, in order for the acoustic vibration propagating through the acoustic vibration portion to propagate through the tubular body portion 1 as a plane wave, the inner side surface of the closed end wall 8 is preferably a flat surface. From the same point of view, it is desirable that the inner side surface of the closed end wall 8 is configured to be orthogonal to the axial direction of the tube portion 1.

  The internal space of the tube part 1 is divided into three air chambers 4a, 4b, and 4c by diaphragms 3b and 3c. Therefore, the three air chambers 4 are arranged in series along the axis of the tube part 1. Among these three air chambers 4, in the air chamber 4c disposed at the end, the diaphragm 3c is disposed on one side, and the closed end wall 8 is disposed on the other side.

  A through hole 11 is provided in the side wall of the tube portion 1 of the acoustic transmission path 10 for the driver unit 20 to be acoustically coupled to the acoustic transmission path. The through hole 11 is disposed so as to communicate the air chamber 4 c adjacent to the closed end wall 8 and the outside world. Therefore, the driver unit 20 is coupled to the air chamber C adjacent to the closed end wall 8.

  The speaker system 30 of the present embodiment configured as described above has the following operational effects.

  The acoustic transmission path 10 in the speaker system 30 of the present embodiment has the diaphragms 3a, 3b, 3c arranged at the positions of the adjacent mass points 1A, 1B, 1C in the dynamic model shown in FIG. This corresponds to the case where the closed end wall 8 is disposed at the position. According to the graph of FIG. 2, when the wave number is π / 2L, a standing wave having a total tube length of 3/4 wavelength can be established at a distance from 1A to 1C. Although not shown in the graph of FIG. 2, when the wave number is π / 6L, a standing wave can be established in which the entire tube has a quarter wavelength.

  Also in the acoustic transmission line 10 in the present embodiment, a low propagation speed of 1/3 or less of the sound speed in the atmosphere can be easily obtained, so that the resonance frequency is 100 Hz or less and the total length of the tubular body 1 is 0.25 mm. The following 1/4 wavelength resonance tube can be easily configured.

  Here, the Example performed in order to confirm the effect of the speaker system 30 of this embodiment is shown. The tube portion 1 is a cylindrical tube having an inner diameter of 0.09 m, and the lengths L of the air chambers 4a, 4b, and 4c are all 0.11 m. The effective diameter of each diaphragm 3a, 3b, 3c was 0.064 m. The mass of the diaphragm 3a arranged at the end was 16 g, and the mass of the diaphragms 3b and 3c arranged inside the tube body 1 was 20 g. The spring constant of the edge member 7 was set to So = 790 N / m for all the diaphragms 3a, 3b, and 3c. When this spring constant is converted to Vas (equivalent capacity), it is about 1.9 liters, which is larger than the capacity of the adjacent air chambers 4a, 4b, 4c is about 0.7 liters. Therefore, the relatively high elasticity of the downsized air chamber 4 is dominant as the elastic element, and the effect of increasing the resonance frequency by the edge member 7 added thereto is relatively small.

  In the present embodiment, the movable range of all the diaphragms 3a, 3b, and 3c was ± 2.5 mm, and a large value was secured for the diaphragms 3a, 3b, and 3c having an effective diameter of 0.064 m. This has the effect that the diaphragm 3a arranged at the end can be oscillated with a margin as an antinode of a standing wave. Note that a small movable range may be set for the inner diaphragms 3b and 3c in comparison with the diaphragm 3a.

  The Qms of the vibration system including the diaphragms 3a, 3b, 3c and the edge member 7 was set to 5.2. The driver unit 20 has an effective diameter of 0.064 m, fs = 110 Hz, and Qts = 0.33.

  When correction is applied to the equations (10) and (11) assuming an infinite system in consideration that the effective vibration area of each of the diaphragms 3a, 3b, and 3c is 51% of the cross-sectional area in the tube, the wavelength 4L ( At a wave number of π / 2L), the frequency of element vibration is calculated as 85 Hz and the phase velocity Vp as 37 m / s. At a wavelength of 12 L (wave number π / 6 L), the frequency of element vibration is calculated as 31 Hz, and the phase velocity Vp is calculated as 41 m / s. In contrast, in an actual system composed of a finite number of mass elements, resonance was observed at 65 Hz and 24 Hz from impedance measurement.

  In the present embodiment, it is possible to configure an acoustic transmission path corresponding to a quarter wavelength at a frequency of 24 Hz with a total length of only 0.33 m. Since the total length of the air column resonance tube corresponding to a quarter wavelength that resonates with a sound wave having a frequency of 24 Hz is about 3.5 m, it can be significantly shortened. In addition, an ordinary air column resonance tube resonates at a plurality of frequencies corresponding to the fundamental resonance frequency and its harmonics, whereas in this embodiment, only a harmonic resonance of 65 Hz exists. Yes. In addition, since the driver unit 20 has substantially no sound output at 24 Hz, it was possible to obtain an increase in sound pressure due to resonance amplification only at 65 Hz.

(13th Embodiment)
In the configuration of the speaker system of the twelfth embodiment shown in FIG. 16, the thirteenth embodiment is a so-called transmission line type speaker by actively increasing the transmission loss in the tube and absorbing and removing the backside radiation. It is a system configuration. In order to positively increase the transmission loss, the speaker system of the twelfth embodiment shown in FIG. 16 is used except that the Qms of the vibration system including the diaphragms 3a, 3b, 3c and the edge member 7 is reduced. Same as the case. Therefore, the same reference numerals are used for similar configurations, and repeated description is omitted.

  In the speaker system of this embodiment, in order to reduce the Qms of the vibration system composed of the diaphragms 3a, 3b, 3c and the edge member 7, a damping material (not shown) such as silicone rubber is used for the diaphragms 3a, 3b, 3c. And applied to the surface of the vibration system composed of edge members.

  The purpose of the transmission line system as in the present embodiment is to adjust the sound quality, and the main purpose is to obtain bass suppression by braking rather than resonance bass enhancement. In the normal transmission line system, a relatively long full-length pipe body part is required in order to increase the transmission loss in the pipe by filling the pipe with a sound absorbing material while having the basic structure of the resonance pipe system.

  On the other hand, if the resonance tube type speaker system of this embodiment is used as a basis, not only the overall length of the tube body 1 can be greatly shortened, but also by reducing the Qms of the vibration system composed of the diaphragm and the edge. Transmission loss in the pipe can be easily increased.

(Fourteenth embodiment)
FIG. 17 is a cross-sectional view of a speaker system according to a fourteenth embodiment of the present invention. The speaker system of this embodiment is an example of a closed resonance tube in which one end of a transmission path is a driver unit 20 and the other end is a closed end. That is, in the speaker system of the present embodiment, the driver unit 20 is disposed at one end of the tube body portion 1, and the closed end wall surface is provided at the other end of the tube body portion 1.

  The speaker system 30 of the present embodiment configured as described above has the following operational effects.

  In the acoustic transmission path 10 in the speaker system 30 of the present embodiment, in the dynamic model shown in FIG. 2 described above, the driver unit 20 is disposed at the position of the adjacent mass point 1A, and each diaphragm 3b, This corresponds to the case where 3c is arranged and the closed end wall 8 is arranged at the 1D position. According to the graph of FIG. 2, when the wave number is π / 2L, a standing wave having a total tube length of 3/4 wavelength can be established at a distance from 1A to 1C. Although not shown in the graph of FIG. 2, when the wave number is π / 6L, it is possible to establish a standing wave that substantially makes the entire tube a quarter wavelength.

  Here, the Example performed in order to confirm the effect of the speaker system 30 of this embodiment is shown. The tube portion 1 is a cylindrical tube having an inner diameter of 0.09 m, and the lengths L of the air chambers 4a, 4b, and 4c are all 0.11 m. The effective diameter of each diaphragm was 0.064 m. The mass of the diaphragm 3a of the driver unit 20 disposed at the end of the tubular body 1 was 8 g, and the mass of the diaphragms 3b and 3c disposed inside the tubular body 1 was 10 g. The spring constant of the edge member 7 was S0 = 790 N / m in common for all the diaphragms 3a, 3b, 3c. Here, in this example, the movable range of all the diaphragms 3a, 3b, and 3c was ± 5.0 mm, and a large value was secured for the diaphragm having an effective diameter of 0.064 m. This has the effect that the diaphragm 3a arranged at the end can be amplified with a margin as an antinode of a standing wave. A small movable range may be set for the inner diaphragms 3b and 3c in comparison with the diaphragm 3a.

  The Qms of the vibration system including the diaphragms 3a, 3b, 3c and the edge member 7 was set to 5.2. The driver unit 20 used was fs = 50 Hz and Qts = 0.28.

  When correction is applied to the equations (10) and (11) assuming an infinite system in consideration that the effective vibration area of each of the diaphragms 3a, 3b, and 3c is 51% of the cross-sectional area in the tube, the wavelength 4L ( At a wave number of π / 2L), the frequency of element vibration is calculated to be 119 Hz, and the phase velocity Vp is calculated to be 52 m / s. At a wavelength of 12 L (wave number π / 6 L), the frequency of element vibration is calculated as 43 Hz, and the phase velocity Vp is calculated as 57 m / s. In contrast, in an actual system composed of a finite number of mass elements, resonance was observed at 90 Hz and 33 Hz from impedance measurement. A strong antiresonance was observed at 64 Hz.

  In the present embodiment, it is possible to configure an acoustic transmission path corresponding to a quarter wavelength at a frequency of 33 Hz with a total length of only 0.33 m. Since the total length of the air column resonance tube corresponding to a quarter wavelength that resonates with a sound wave having a frequency of 33 Hz is about 2.5 m, it can be significantly shortened. In addition, an ordinary air column resonance tube resonates at a plurality of frequencies corresponding to the fundamental resonance frequency and its harmonics, whereas in this embodiment, only a harmonic resonance of 90 Hz exists. Yes.

  In the above first to fourteenth embodiments, the case where one acoustic transmission path and one driver unit are provided has been described. However, the acoustic transmission path and the speaker system of the present invention include a plurality of acoustic transmission paths and a plurality of acoustic transmission paths. You may have a some driver unit. In the fifteenth to seventeenth embodiments below, a case where a plurality of acoustic transmission paths are provided will be described.

(Fifteenth embodiment)
FIG. 18 is a cross-sectional view of the speaker system of the fifteenth embodiment of the present invention. In this embodiment, in the speaker system of the third embodiment, a second driver unit 20b is added to the front surface of the first driver unit 20 via a second driver container 12b. Here, the speaker system itself of the present embodiment is the same as the speaker system of the third embodiment, except that the second driver unit 20b is added via the second driver container 12b. Therefore, in the following description, the same code | symbol is used about the same structure, and repeated description is abbreviate | omitted.

  The second driver container 12 b is formed on the front side of the first driver unit 20. A first driver unit 20 is provided on the proximal end side (side closer to the acoustic transmission path 10) of the second driver container 12b, and a second driver unit 20b is provided on the distal end side of the second driver container 12b. ing.

  In the case shown in FIG. 18, the wall portion that forms the second driver container 12 b extends from the installation position of the first driver unit 20, that is, from the central portion along the axial direction of the tube portion 1. It extends while being bent to the vicinity of the diaphragm 3a arranged at the end of the. Therefore, in the example shown in FIG. 18, the second driver unit 20 b is disposed in proximity to the diaphragm 3 a at one end of the acoustic transmission path 10. The second driver unit 20b is not limited to the case where the second driver unit 20b is disposed close to the diaphragm 3a, but may be disposed close to the diaphragm 3d, or the reproduced sound wave from both the diaphragms 3a and 3d. You may arrange | position within the distance small enough compared with a wavelength. Further, the second driver unit 20 b arranged in this way is driven by an electric signal in phase with the first driver unit 20.

  The effect of the speaker system 30 of this embodiment comprised as mentioned above is demonstrated.

  According to the speaker system 30 of the present embodiment, the back pressure generated in the second driver container 12b by the second driver unit 20b is removed by the movement of the first driver unit 20 that swings in phase. At this time, the back pressure of the second driver unit 20b is transmitted to the first driver unit 20 through the movement of air in the second driver container 12b, and is transferred to the back pressure of the first driver unit 20. The The back pressure of the first driver unit 20 is transmitted to the acoustic transmission path 10 through the through hole 11 and then released to the outside from the diaphragms 3 a and 3 d provided at the end of the tube body 1.

  Therefore, the speaker system 30 of the present embodiment is equivalent to the case where an infinitely large cabinet is connected behind the second driver unit 20b, so the second driver unit 20b having a small aperture and vibration system mass is used. However, there is an effect that efficient bass reproduction is possible.

  Moreover, in the speaker system 30 of this embodiment, at least a part of the acoustic transmission path 10 is used as a phase shifter. That is, the back pressure of the first driver unit 20 generated as a result of removing the back pressure of the second driver unit 20b is a process in which the back pressure of the first driver unit 20 propagates in the acoustic transmission path 10 having a slow propagation speed compared to the sound speed in the atmosphere. There is a delay in the phase. Therefore, a phase relationship is set in which the sound waves emitted to the outside from the diaphragms 3a and 3d provided at the end of the tubular body portion 1 and the sound waves emitted from the front surface of the second driver unit 20b are intensified. It is possible.

  For example, in the second driver unit 20b, a back-surface radiated sound wave having a phase difference of 180 degrees with respect to the front-surface radiated sound wave is delayed by 90 degrees in the acoustic transmission path 10 and then provided at the end of the tubular body portion 1. When emitted from the diaphragms 3a and 3d to the outside, the sound wave emitted from the front surface of the second driver unit 20b has a total phase difference of 270 degrees. Therefore, the sound pressure can be increased compared to the case where either the second driver unit 20b or the diaphragm 3a (or 3d) at the end radiates sound waves alone.

  For example, when the acoustic transmission path 10 having a full length corresponding to a half wavelength at a frequency of 46 Hz is configured, in the example shown in FIG. 18, the acoustic length of the path from the second driver unit 20b to the diaphragm 3a is small. Since it corresponds to a quarter wavelength at a frequency of 46 Hz, it acts as a 90-degree phase shifter, and the above-described sound pressure enhancement effect can be obtained. Further, the sound pressure enhancement effect can be obtained even at each frequency where the phase shift amount is 60 degrees or more.

  As described above, the speaker system according to the present embodiment has been described. However, various modifications are possible, and the second driver unit 20b is mounted on the front surface of the first driver unit 20 with the second driver container 12b interposed. As long as they are added, various speaker systems can be configured.

(Sixteenth embodiment)
FIG. 19 is a cross-sectional view of the speaker system of the sixteenth embodiment. The speaker system of this embodiment is obtained by adding a second acoustic transmission path 10b in addition to the first acoustic transmission path 10 to the speaker system of the third embodiment. Specifically, openings 19 and 19b are respectively provided on the side wall of the tube portion 1 of the first acoustic transmission path 10 and the side wall of the tube portion 1b of the second acoustic transmission path 10b. A diaphragm 3J and a diaphragm 3K are provided in the opening as mass elements, respectively. The openings provided with the diaphragm 3J and the diaphragm 3K are communicated with each other through the connecting pipe 1c. Except for the above points, the configuration of the speaker system 30 of the thirteenth embodiment is the same as that of the speaker system 30 of the third embodiment and the acoustic transmission path 1 of the first embodiment. Therefore, in the following description, the same code | symbol is used about the same structure, and repeated description is abbreviate | omitted.

  As shown in FIG. 19, the speaker system 30 of the present embodiment includes a first acoustic transmission unit 10 and a second acoustic transmission unit 10 b. The first acoustic transmission path 10 includes diaphragms 3a, 3b, 3c, and 3d, and includes three air chambers 4a, 4b, and 4c defined by the diaphragms 3a, 3b, 3c, and 3d. Of these air chambers 4a, 4b, 4c, the air chamber 4b arranged in the center is provided with a through hole 11, and the driver unit 20 has a tube portion 1 so that its back surface faces the through hole 11. It is arranged on the outside of the side wall.

  Further, the opening 19 is provided on the side wall of the tubular body 1 at a position facing the through hole 11, that is, the driver unit 20, and the opening 3 is provided with a diaphragm 3 j. That is, the diaphragm 3j is provided in the opening 19 of the air chamber 4b arranged in the center.

  On the other hand, the tube portion 1b of the second acoustic transmission unit 10b includes diaphragms 3e, 3f, 3g, and 3h, and three air chambers 4e and 4f that are partitioned by the diaphragms 3e, 3f, 3g, and 3h. 4g. Of these air chambers 4e, 4f, and 4g, the air chamber 4f disposed in the central portion is provided with an opening 19b at a position facing the opening 19 of the first acoustic transmission unit 10, and the opening 19b has an opening 19b. Is provided with a diaphragm 3k. That is, the diaphragm 3k is provided in the opening 19b of the air chamber 4f disposed in the center.

  A communication pipe 1c is provided between the tube part 1 and the tube part 1b so as to communicate the opening 19 and the opening 19b. A space defined by the communication pipe 1c and the diaphragms 3j and 3k forms a new air chamber 4j and forms a third acoustic transmission path including the diaphragms 3J and 3K. Therefore, the first acoustic transmission path 10 and the second acoustic transmission path 10b are coupled via the third acoustic transmission path. Here, the diaphragms 3 j and 3 k have the same area and mass as the diaphragms 3 b and 3 c in the tubular body portion 1, and the air chamber 4 j is also the same as the air chamber 4 of the first acoustic transmission path 10. Equivalent cross-sectional area and air chamber length. That is, the speaker system 30 of the present embodiment includes first, second, and third acoustic transmission paths as acoustic transmission paths, and the tube portions 1 of the first and second acoustic transmission paths 10, 10b, It can be said that 1b is connected via the tube part 1c of the third acoustic transmission path.

  In the present embodiment, both the first acoustic transmission path 10 and the second acoustic transmission path 10b are configured as ½ wavelength resonance tubes having the same resonance frequency, for example, 46 Hz.

  The effect of the speaker system 30 of this embodiment comprised as mentioned above is demonstrated.

  A third acoustic transmission path, that is, a path from the back surface of the driver unit 20 through the diaphragm 3j to the diaphragm 3k acts as a phase shifter of 90 degrees at a resonance frequency, for example, 46 Hz.

  In the driver unit 20, backside sound waves having a phase difference of 180 degrees with respect to the front surface sound waves cause a phase delay of 90 degrees in the third acoustic transmission path, and further a phase delay of 90 degrees in the second acoustic transmission path. After it has occurred, it is discharged to the outside from the diaphragms 3e and 3h provided at the end of the tube portion 1b in the second acoustic transmission path. Therefore, the sound wave emitted from the entire surface of the driver unit 5 and the sound wave emitted outside from the diaphragms 3e and 3h have a total phase difference of 360 degrees, that is, the same phase, so that a strong sound pressure enhancing effect is obtained. be able to.

  Thus, in the speaker system of the present embodiment, the first to third acoustic transmission paths are provided, and the second acoustic transmission path that is one of the plurality of acoustic transmission paths is provided. It can be said that the first to third acoustic transmission paths are coupled to each other so that the sound waves emitted from the end diaphragms 3e and 3H and the sound waves emitted from the front surface of the driver unit 20 are in phase. .

  In the present embodiment, the linear acoustic transmission paths 10 and 10b are employed for the purpose of maximizing the resonance efficiency and minimizing the acoustic reaction, but it is allowed to reduce the resonance efficiency. In some cases, the acoustic transmission paths 10 and 10b may be bent at least partially for the purpose of further miniaturization. For example, the first acoustic transmission path 10 is bent 90 to 120 degrees in the central air chamber 4b, and the second acoustic transmission path is bent 90 to 120 degrees in the central air chamber 4f, thereby reducing the installation area. Is possible.

(Seventeenth embodiment)
FIG. 20 is a cross-sectional view of the speaker system of the seventeenth embodiment. The speaker system of this embodiment is the same as that of the speaker system of the third embodiment, the second driver unit 20b coupled to the same air chamber 4b as the first driver unit 20, and the back surface of the second driver unit 20b. And a second acoustic transmission line coupled to the. Except for the above points, the configuration of the speaker system 30 of the thirteenth embodiment is the same as that of the speaker system 30 of the third embodiment and the acoustic transmission path 1 of the first embodiment. Therefore, in the following description, the same code | symbol is used about the same structure, and repeated description is abbreviate | omitted.

  As shown in FIG. 20, the speaker system 30 of the present embodiment includes a first acoustic transmission unit 10 and a second acoustic transmission unit 10b. The first acoustic transmission path 10 includes diaphragms 3a, 3b, 3c, and 3d, and includes three air chambers 4a, 4b, and 4c defined by the diaphragms 3a, 3b, 3c, and 3d. Of these air chambers 4 a, 4 b, 4 c, the air chamber 4 b disposed in the center is provided with a through hole 11, and the first driver unit 20 has a tubular body with its back surface facing the through hole 11. It is arranged outside the side wall of the part 1. Similarly to the first acoustic transmission path 10, the second acoustic transmission path 10b includes diaphragms 3e, 3f, 3g, and 3h, and three airs partitioned by the diaphragms 3e, 3f, 3g, and 3h. It has chambers 4e, 4f, 4g. Of these air chambers 4e, 4f, and 4g, the air chamber 4f disposed in the center is provided with a through hole 11, and the second driver unit 20b has a tubular body so that the back surface thereof faces the through hole 11b. It arrange | positions on the outer side of the side wall of the part 1b.

  The air chamber 4b, which is the same as the first driver unit 20, is provided with a through hole 18 for the second driver unit 20b. For example, the through hole 18 for the second driver unit 20b can be provided at a position facing the through hole 11 for the first driver unit 20 on the side wall of the tubular body portion 1. Then, the second driver unit 20b is arranged so that the front surface of the second driver unit 20b faces the new through hole 18 provided in the air chamber 4b. Are connected. That is, the speaker system 30 of the present embodiment includes the first and second acoustic transmission paths 10 and 10b as the acoustic transmission paths, and the first and second driver units 20 and 20b as the electroacoustic transducers. The tubular body portion 1 of the first acoustic transmission path 10 to which the first driver unit 20 is coupled and the tubular body section 1b of the second acoustic transmission path 10b are connected via the second driver unit 20b. It can be said that.

  Note that a second driver container 12b is formed on the front surface of the second driver unit 20b, and the wall surface forming the second driver container 12b surrounds the second driver unit 20b, and the first and second driver containers 20b. The tube parts 1, 1b of the acoustic transmission parts 10, 10b are connected.

  Here, the first acoustic transmission unit 10 and the second acoustic transmission unit 10b are set to have different resonance frequencies. Further, the first driver unit 20 and the second driver unit 20b are driven by electric signals having opposite phases.

  The effect of the speaker system 30 of this embodiment comprised as mentioned above is demonstrated.

  According to the speaker system 30 of the present embodiment, by having the first acoustic transmission path 10 and the second acoustic transmission path 10b which are a plurality of acoustic transmission paths set to have different resonance frequencies, As compared with a single acoustic transmission line, the sound pressure enhancement effect due to resonance can be obtained in a wider frequency range.

(Eighteenth embodiment)
FIG. 21 is a cross-sectional view of the speaker system of the eighteenth embodiment. This embodiment is another example in which a second acoustic transmission path is added to the speaker system of the third embodiment. In the present embodiment, the first acoustic transmission path 10 including the diaphragms 3a, 3b, 3c and 3d and the second acoustic transmission path 10b including the diaphragms 3e, 3f, 3g and 3h share the air chamber 4b. And are driven by a common driver unit 20.

  Of the three air chambers 4a, 4b, 4c of the first acoustic transmission path 10, a through hole 11 is provided in the air chamber 4b disposed in the center, and the back surface of the driver unit 20 is a through hole. 11 is disposed on the outside of the side wall of the tubular body 1 so as to face 11. The air chamber 4b is provided with a pair of openings 19 and 19b facing each other on the side wall of the tube portion 1. The opening 19 is provided with a diaphragm 3f, and the opening 19b is provided with a diaphragm 3g.

  A new air chamber 4e is provided adjacent to the diaphragm 3f, and the tube portion 1b extends from the tube portion side wall of the first acoustic transmission path 10 so as to partition the air chamber 4e from the outside. A diaphragm 3e is provided on the distal end side of the tubular body 1b so as to face the diaphragm 3f. Similarly, a new air chamber 4g is provided adjacent to the diaphragm 3f, and the tube portion 1c extends from the tube portion side wall of the first acoustic transmission path 10 so as to partition the air chamber 4g from the outside. ing. A diaphragm 3h is provided on the distal end side of the tubular body portion 1c so as to face the diaphragm 3g.

  According to such a configuration, the diaphragms 3e, 3f, 3g, and 3h serving as mass elements and the air chambers 4e, 4b, and 4g defined by the diaphragms 3e, 3f, 3g, and 3h are provided with the second acoustic wave. A transmission line 10b is formed. The second acoustic transmission path 10b shares the air chamber 4b disposed at the center among the three air chambers 4e, 4b, and 4g with the first acoustic transmission path 10, and the shared air chamber 4b. The driver unit 20 is coupled to the above.

That is, the speaker system of the present embodiment includes first and second acoustic transmission paths as the acoustic transmission path, and each tubular body portion of the first and second acoustic transmission paths has one air chamber. The electroacoustic exchanger is coupled to an air chamber shared by each tubular body portion of the first and second acoustic transmission paths, and is arranged so as to cross over in common. Here, the first acoustic transmission path 10 and the second acoustic transmission path 10b are set to have different resonance frequencies. That is, in the speaker system 30 of the present embodiment, the first acoustic transmission path 10 and the second acoustic transmission path 10b set so as to have different resonance frequencies share one air chamber 4b and cross over each other. The driver unit is coupled to one air chamber 4b shared by the first acoustic transmission path 10 and the second acoustic transmission path 10b.

  According to the speaker system 30 of the present embodiment configured as described above, the first acoustic transmission path 10 and the second acoustic transmission path resonate at different frequencies, so that compared to a single acoustic transmission path. A sound pressure enhancement effect by resonance can be obtained in a wide frequency range.

(Nineteenth embodiment)
This embodiment relates to a tube module for an assembly kit of an acoustic transmission path 10 as shown in FIG. The tubular body module is provided at the tubular part, at least one diaphragm 3a provided so as to vibrate in the axial direction of the tubular part inside the tubular part, and at one end and the other end of the tubular part. And first and second joint portions. Here, the first joint is a male joint, and the second joint is a female joint that is paired with the male joint.

  For example, by preparing a plurality of tube modules each provided with the diaphragm 3 at least one by one, and connecting the first and second joint portions of the plurality of tube modules detachably, An acoustic vibration unit 10 in which the air chambers 4a, 4b, and 4c partitioned by the diaphragm 3 are alternately arranged is configured. Also in this case, as described in the first embodiment, due to the periodicity of the arrangement of the diaphragm 3 and the air chambers 4a, 4b, and 4c, the propagation speed of the acoustic vibration propagating through the acoustic vibration unit 10 is 20 Hz. In the frequency range of 200 Hz or less, it becomes 1/3 or less of the sound speed in the atmosphere. The user can enjoy the desired sound quality by changing the number of tube modules to be connected.

  Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these cases, and various modifications, omissions, and additions are possible.

It is sectional drawing of the acoustic transmission path of the 1st Embodiment of this invention. It is a figure which shows the mode of the mechanical model corresponding to the acoustic transmission path of FIG. 1, and the element vibration which propagates this mechanical model. It is sectional drawing of the acoustic transmission path of the 2nd Embodiment of this invention. It is sectional drawing of the speaker system of the 3rd Embodiment of this invention. It is sectional drawing which shows the example which provided the sound-absorbing material in the speaker system of FIG. It is the figure which showed typically the pressure amplitude of the standing wave in the tube part in the speaker system of FIG. It is sectional drawing of the speaker system of a 1st comparative example. It is sectional drawing of the speaker system of a 2nd comparative example. It is sectional drawing of the speaker system of the 4th Embodiment of this invention. Sectional drawing of the speaker system of the 6th Embodiment of this invention. It is sectional drawing of the speaker system of the 7th Embodiment of this invention. It is sectional drawing of the speaker system of the 8th Embodiment of this invention. It is sectional drawing of the speaker system of the 9th Embodiment of this invention. It is sectional drawing of the speaker system of the 10th Embodiment of this invention. It is sectional drawing of the speaker system of the 11th Embodiment of this invention. It is sectional drawing of the speaker system of 12th Embodiment of this invention. It is sectional drawing of the speaker system of 14th Embodiment of this invention. It is sectional drawing of the speaker system of 15th Embodiment of this invention. It is sectional drawing of the speaker system of the 16th Embodiment of this invention. It is sectional drawing of the speaker system of the 17th Embodiment of this invention. It is sectional drawing of the speaker system of the 18th Embodiment of this invention.

Explanation of symbols

1 tube part,
3a, 3b, 3c, 3d diaphragm,
4a, 4b, 4c air chamber,
5a, 5b end walls,
6a, 6b Bulkhead,
7 Edge member,
8 closed end wall,
9 Open end,
10 acoustic transmission path,
11 through holes,
12 Driver container,
13a, 13b Port pipe 14 Sound absorbing material,
15 Vibration membrane 16 Reinforcement frame 18 Port pipe,
19, 19b opening,
20 driver unit,
30 Speaker system.

Claims (7)

A tubular body portion having an axial length larger than the inner diameter and having at least one open end, and mass elements and elastic elements are alternately arranged in the axial direction of the tubular body portion within the tubular body portion. A frequency of propagation of acoustic vibrations propagating through the acoustic vibration part inside the tubular part due to the periodicity of the arrangement of the mass elements and the elastic elements. An acoustic transmission line that is 1/3 or less of the speed of sound in the atmosphere in the range;
And an electroacoustic exchanger acoustically coupled to the acoustic transmission path. The electro-acoustic exchanger speaker system according to claim 1, characterized in that it is acoustically coupled to the interior of the tube body portion in the acoustic transmission path so as not to divide the axial direction of the tube body portion . The electroacoustic exchanger is acoustically coupled to the acoustic transmission path in the middle of the arrangement of the mass element and the elastic element so as not to divide the arrangement of the mass element and the elastic element. The speaker system according to claim 2 . The tube part is one that is open at both ends,
The speaker system according to claim 3 , wherein the mass elements are arranged at both ends of the tubular body portion. 5. The speaker system according to claim 4 , wherein a standing wave of the acoustic vibration having an axial length of the tube portion substantially ½ wavelength is established in the tube portion. . The elastic element is an air chamber provided inside the tubular body part,
The speaker system according to claim 4 , wherein three or more partitioned air chambers are arranged in series. An odd number of the air chambers are arranged in series,
The speaker system according to claim 6 , wherein the electroacoustic exchanger is coupled to an air chamber arranged in the center of the odd number of air chambers.