JPH0711758B2 - Portable electric instruments - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable electric musical instrument, and more particularly to a portable electric musical instrument capable of generating heavy bass while having a size and shape suitable for carrying and standing.

[Prior Art] Conventionally, as a portable electric musical instrument, in a musical instrument such as a guitar or a drum, which has a resonator in its main body and can directly generate a musical sound, the musical sound is By converting the signal into a signal, electrically amplifying it, re-converting it into sound with an audio device, and then pronouncing it, a musical sound can be pronounced louder than that directly generated, or a special effect can be added. It is known that it can be processed and pronounced.

[Problems to be Solved by the Invention] By the way, in such a portable electric musical instrument, the main body is required to be small in size to some extent in view of the ease of carrying and standing, and the small main body is small. Since the speaker unit having the caliber is provided, there is a disadvantage that only a poor sound without low sound can be generated. In addition, there is also known a portable electric musical instrument of a type that has a resonator dedicated to an acoustic device or used for the acoustic device and a resonance commonly used for the musical instrument to produce a low tone inside the main body. However, in such a type of instrument, if an attempt is made to obtain sufficient sound quality, the body becomes large like an acoustic guitar and is not always suitable for standing, but on the other hand, if the size is suitable for standing, sufficient sound quality is achieved. There was an inconvenience that I could not get.

In view of the drawbacks of the conventional example, an object of the present invention is to realize a portable electric musical instrument which has a size suitable for being carried and produces a heavy bass.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, a resonance frequency originally provided in a portable electric musical instrument main body is provided as it is, or if necessary, an acoustic mass means is provided to reduce a resonance frequency. A vibrating body that is modified and shared for use in an acoustic device, and this resonator constitutes a part of this resonator to drive this resonator on one side and emit sound directly from the other side to the outside of the instrument body. A vibrator provided with, and further provided with a vibrator driving means for driving the vibrator so as to cancel a reaction from the resonator to the diaphragm of the vibrator when the resonator is driven, thereby, The resonance of the resonator is used more positively.

[Operation] A sound device for a conventional portable electric musical instrument includes a speaker system and a power amplifier that drives the speaker system in a so-called constant voltage and has an output impedance of substantially zero. Therefore, in these musical instruments, the output sound pressure characteristic is affected by the volume of the cavity behind the diaphragm of the speaker unit, and if the volume of the cavity is reduced in order to downsize the resonator and the instrument body, the bass characteristic is impaired. was there.

In the present invention, the drive means drives the vibrator so as to cancel the action of the vibrator from the resonator side. That is, the vibrator is driven in a so-called dead state in which it is sufficiently damped without being affected by the action from the resonator side. Therefore, the frequency characteristics of the direct radiated sound are not affected by the volume of the space behind the direct radiation surface of the vibrator, and this volume of space is not inconvenient for the cavity of the resonator and the container of the vibrator. , Can be made smaller. When viewed from the resonator side, driving the oscillator so as to cancel the atmospheric reaction from the resonator side when driving the resonator means that the diaphragm of the oscillator cannot be driven from the resonator side. It means that it has become a wall. Therefore, the Q value of the resonator is not affected by the characteristics (f _O , Q _O ) of the vibrator, and a sufficiently high Q value can be secured even if the resonance frequency is lowered. As a result, even if the size of the resonator, and hence the body of the musical instrument, is reduced, it is possible to generate a sufficient low-pitched sound (resonance sound) from the resonator.

[Effect] As described above, according to the present invention, the resonance of the resonator in the main body is positively used while the small-sized instrument main body having the resonator inside the main body is provided with the small-diameter speaker unit. By doing so, it is possible to obtain a sound quality with a sufficient bass characteristic. Further, if the present invention is applied to a large-sized portable electric instrument such as an acoustic guitar, the resonator can be downsized and the instrument body can be downsized to a level suitable for standing without impairing the sound quality. You can

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic construction of a portable electric musical instrument according to an embodiment of the present invention. In the electric musical instrument of the same figure, a duct 6a having an opening port 9a is provided on the upper surface of the musical instrument housing 1, and a cavity 5 and a duct 6a in the musical instrument housing 1 constitute a Helmholtz resonator, and the vicinity of the opening port 9a. A drum membrane for driving the Helmholtz resonator, a sounding device 2 such as a string or a lead of a guitar, etc. is provided in the left side of the musical instrument casing 1 and a vibrating plate 3 is provided on the left side of the musical instrument casing (dynamic type). Speaker unit) 4
And a sounding circuit 7 such as a pickup for converting mechanical or acoustic vibration of the sounding device 2 into an electric signal, and a vibrator for driving the vibrator 4 based on the electric signal supplied from the sounding circuit 7. The drive circuit 8 is provided.

In the Helmholtz resonator, a closed cavity 5
An air resonance phenomenon occurs due to the air spring inside and the air mass inside the duct 6. And this resonance frequency f _OP is Can be asked as Here, V ₁ is the volume of the cavity 5, S ₁ is the cross-sectional area of the duct 6a, l ₁ is the length of the duct 6a, and c is the speed of sound.

The Helmholtz resonator and the vibrator 4 constitute a speaker system (hereinafter referred to as a speaker system with a resonance port) which is similar in shape to a conventional phase inversion (bass reflex) speaker system.

The vibrator drive circuit 8 drives the vibrator 4 so as to cancel the atmospheric action from the Helmholtz resonator, that is, the cavity 5 side when the Helmholtz resonator is driven. Such drive devices, equivalently detect and enter some way a motional signal corresponding to the movement of the negative impedance generator or vibrator for generating a negative impedance component (-Z _O) in the output impedance A known circuit such as a motional feedback (MFB) circuit that negatively feeds back to the side can be applied.

Next, the operation of the portable electric musical instrument shown in FIG. 1 will be described.

When the sounding device 2 is operated during the performance of this electric musical instrument, mechanical vibration is generated in the sounding device 2. This mechanical vibration activates the Helmholtz resonator through the opening port 9a and is converted into an electric signal by the sounding circuit 7. The vibrator driving circuit 8 drives the vibrator 4 based on the electric signal supplied from the sounding circuit 7. As a result, the resonance sound of the mechanical vibration of the sounding device 2 is directly emitted from the Helmholtz resonator, and the musical sound of the volume amplified via the speaker system with the resonance port including the vibrator 4 and the Helmholtz resonator is generated. Is pronounced.

It should be noted that the Helmholtz resonator has a volume that is sufficient to tune the musical instrument by the resonance cavity 5 of the musical instrument itself even when the sounding circuit 7 and the vibrator driving circuit 8 are turned off, or to allow the performer to confirm the performance content himself. Can occur.

When a drive signal is applied from the vibrator drive circuit 8 to the vibrator 4, the vibrator 4 electromechanically converts the drive signal to drive the diaphragm 3 back and forth (left and right in the figure). The diaphragm 3 converts this reciprocating motion into mechanical sound. Here, the front side of the diaphragm 3 (the left side in the figure) forms a direct radiator for directly radiating sound to the outside, and the rear side of the diaphragm 3 (the right side in the figure).
Represents a resonator driving unit for driving the Helmholtz resonator composed of the cavity 5 and the duct 6a. Then, on the rear surface side of the vibration plate 3, the vibration plate 3 from the air in the cavity 5 is removed.
Although an atmospheric reaction is added to the action of, the vibrator driving circuit 8 drives the vibrator 4 so as to cancel this atmospheric reaction.

Thus, when the vibrator 4 is driven so as to cancel the atmospheric reaction from the resonator when the Helmholtz resonator is driven, the diaphragm 3 cannot be driven from the resonator side, and when viewed from the resonator side, Acts as a rigid body or wall. Therefore, the resonance frequency and Q as the Helmholtz resonator are independent of the resonance frequency and Q as the direct radiation portion by the diaphragm 3 and the vibrator 4, and the resonator driving energy from the vibrator 4 is also directly radiated as described above. It will be given independently of the department. Further, since the oscillator 4 is driven in a so-called dead state that is not affected by the atmospheric reaction from the resonator, that is, the cavity 5, the frequency characteristic of the direct radiation sound is not affected by the volume of the cavity 5. Therefore, according to the configuration of this embodiment, the volume of the cavity 5 which is the cavity of the Helmholtz resonator is made smaller than that of the portable electric musical instrument such as the conventional acoustic guitar, and the resonance frequency f _OP is set to be lower than that of the conventional musical instrument. Also, the Q value can be set to a sufficiently large value. As a result, in the portable electric musical instrument of FIG. 1, even if the cavity 5 is made much smaller than the conventional portable electric musical instrument, it is possible to reproduce even lower frequencies.

In FIG. 1, a vibrator 4 drives a diaphragm 3 in response to a drive signal from a vibrator drive circuit 8 and independently drives energy to a Helmholtz resonator composed of a cavity 5 and a duct 6a. give. As a result, sound is directly radiated from the diaphragm 3 as indicated by the arrow a in FIG. 1, and the air in the cavity 5 is caused to resonate, resulting in resonance as indicated by the arrow b in FIG. Sound of sufficient sound pressure is resonantly radiated from the radiating portion (opening port 9a). Then, by adjusting the air equivalent mass in the duct 6a in the Helmholtz resonator, this resonance frequency f _OP is set lower than the reproduction frequency band of the vibrator 4, and the appropriate level of the Q value is adjusted by adjusting the equivalent resistance of the duct 6a. By setting the above, it is possible to obtain the frequency characteristic of the sound pressure as shown in FIG. 2, for example, provided that the sound pressure of an appropriate level is obtained from the opening port 9a. In the figure, a shows the frequency characteristic of the direct radiated acoustic sound pressure from the vibrator 4, and b shows the frequency characteristic of the resonant radiated acoustic sound pressure from the opening port 9a.

As described above, in contrast to the conventional musical instrument having the resonator inside the instrument body, the resonator is attached with the vibrator, and the vibrator is driven so as to cancel the atmospheric reaction from the resonator side. However, by making some changes, it is possible to generate a large-volume musical sound of heavy bass from the conventional instrument body.

FIG. 3 shows a specific example of the portable electric musical instrument of FIG. 4 is a sectional view taken along line II-II of the electric musical instrument shown in FIG. This electric musical instrument uses a small-diameter speaker unit in a so-called semi-acoustic guitar, which is thinner than a conventional acoustic guitar, and is provided with a first duct 6a having a first opening port (sound hole) 9a. No. 2 on the front plate 11 of the guitar sound body (instrument housing) 1
The second duct 6b having the opening port 9b is provided, and the front plate 11 is perforated to attach the speaker unit (vibrator) 4, and the vibration of the guitar string (sound generator) 2 is converted into an electric signal. A pickup (sound generation circuit) 7 and a negative impedance generation circuit (vibrator drive device) 8 for driving the speaker unit 4 are provided.

In the figure, 13 is a tail piece, 14 is a neck, and 15 is a piece.

As described above, by using a part of the reverberation drum 1 of the conventional semi-acoustic guitar as a resonator of the speaker system and driving this speaker system with negative impedance, the bass characteristics of the speaker unit 4 are irrelevant regardless of the characteristics of the speaker unit 4. Extended frequency characteristics can be obtained.

In the portable electric musical instrument shown in FIGS. 3 and 4, the second opening port 9b and the second duct 6b are more suitable for the resonance frequency of the original instrument resonator as the resonator of the acoustic device. It is for changing and setting to a different resonance frequency, and is not necessarily provided when the characteristics of the acoustic device can be sufficiently compensated by setting the characteristics of the vibrator driving device 8. Also, the first duct 6a may have only the opening port 9a, that is, the length l ₁ of the first duct 6a = (thickness of the front plate 11), as in a normal guitar.

Next, the operation of the acoustic device that drives the speaker system using the Helmholtz resonator by the negative impedance generation circuit will be described.

FIG. 5 shows an electrical equivalent circuit of a portion including the vibrator drive circuit 8 shown in FIG. 3 and a speaker system with a resonance port composed of the vibrator 4, the cavity 5 and the ducts 6a and 6b. Here, E _O represents a voltage source that is a drive signal source. The parallel resonance circuit Z ₁ is based on the equivalent motional impedance of the vibrator 4, r _O is the equivalent resistance of the vibration system,
S _O is the equivalent stiffness of the vibration system, and m _O is the equivalent mass of the vibration system. The series resonant circuit Z ₂ is based on the equivalent motional impedance of the Helmholtz resonator constituted by the ducts 6a and 6b and the cavity 5, r _C is the equivalent resistance of the cavity 5, S _C is the equivalent stiffness of the cavity 5, r _P is duct 6a, 6b
Is the combined equivalent resistance of, and m _P is the combined equivalent mass of the ducts 6a and 6b. A is a force factor, when the vibrator 4 is dynamic conductivity type direct radiation speaker, the A = Bl _V a B magnetic flux density in the magnetic gap, when a conductor the entire length of the l _V voice coil. Further, Z _V in the figure is the internal impedance (non-motional impedance) of the vibrator 4, and when the vibrator 4 is an electrodynamic direct radiation speaker unit, it mainly serves as the resistance R _{V of the} voice coil, and a slight inductance. Is included.

FIG. 6 is an electrical equivalent circuit when Z _V −Z _O = 0 in FIG. 5, that is, the internal impedance (non-motional impedance) of the vibrator 4 is equivalently completely nullified. Here, the coefficient attached to the value of each element is omitted.

The following is clear from this equivalent circuit.

First, the parallel resonance circuit Z ₁ having the equivalent motional impedance of the vibrator 4 is AC short-circuited with zero impedance at both ends. Therefore, this parallel resonant circuit Z ₁
Has a Q value of 0 and is virtually no longer a resonant circuit. That is, in this vibrator 4,
The concept of the lowest resonance frequency, which simply had a Helmholtz resonator with the oscillator 4 attached, is no longer present. Hereinafter, when the amount equivalent to the minimum resonance frequency f _O of the vibrator 4 is referred to, the above concept that has been substantially invalidated is merely called. As described above, as a result of the unit resonance system (parallel resonance circuit) Z ₁ being substantially not a resonance circuit, the Helmholtz resonance system (series resonance circuit) Z _{2 is the} only resonance system in this acoustic device.

Further, as a result of the vibration system being substantially a resonance circuit, the vibrator 4 linearly responds in real time to the drive signal input, and does not make a transient response at all. Signal E _O ) is faithfully electromechanically converted,
The diaphragm 3 will be displaced. That is, it is a complete braking state (so-called speaker dead state). In this state, the direct radiation output sound pressure frequency characteristic near the minimum resonance frequency f _O equivalent value of this speaker unit is 6 dB / oct. On the other hand, the characteristic of the normal voltage drive state is 12 dB.
It becomes / oct.

On the other hand, since the series resonance circuit Z ₂ based on the equivalent motional impedance of the Helmholtz resonator is connected to the drive signal source E _O with zero impedance, there is no mutual dependence relationship with the parallel resonance circuit Z _1. , Parallel resonant circuit
Z ₁ and the series resonant circuit Z ₂ will coexist independently and independently. Therefore, the volume of cavity 5 (inversely proportional to S _C )
The shapes and dimensions of the ducts 6a and 6b (proportional to m _P ) do not affect the direct radiation characteristics of the oscillator 4, and the resonance frequency f _CP and the Q value Q _CP of the Helmholtz resonator are equal to those of the oscillator 4. Not affected by equivalent motional impedance. That is, the characteristic value of the Helmholtz resonator and the characteristic value of the vibrator 4 can be set independently. Further, since the series resistance of the series resonance circuit Z ₂ is only r _C + r _P , and these are usually sufficiently small values, the Q value of the series resonance circuit Z ₂ , that is, the Helmholtz resonator is set to be sufficiently high. can do.

From another point of view, the unit vibration system is not actually a resonance system, so it is displaced according to the drive signal input,
It is virtually unaffected by external forces, especially atmospheric reaction due to the equivalent stiffness S _C of the cavity 5. Therefore, the diaphragm 3 of the vibrator 4 is equivalently a wall when viewed from the cavity 5 side, and the existence of the vibrator 4 when viewed from the Helmholtz resonator is nullified. Therefore, the resonance frequency and the Q value as the Helmholtz resonator do not depend on the non-motional impedance of the vibrator 4, and the resonance frequency is set to a frequency at which the Q value of the resonance becomes very small in the usual driving method. Also in the case of performing, the Q value can be maintained at a sufficiently large value. Further, the Helmholtz resonance system is also a virtual speaker that emits sound independently of the unit vibration system. Even though this virtual speaker is realized with a small diameter corresponding to the port diameter, it is equivalent to an extremely large diameter speaker unit as an actual speaker unit in view of its bass reproduction capability.

Comparing the above with a conventional system in which a speaker system with a bass reflex type or a resonator as used in the acoustic guitar is driven by a normal power amplifier, in the conventional system, as is well known, the unit vibration system Z ₁ And a Helmholtz resonance system Z ₂ exist, and the resonance frequency and Q value of each resonance system are closely dependent on each other. For example, if the ducts 6a and 6b are made longer or thinner (m _P becomes larger) in order to lower the resonance frequency of the Helmholtz resonance system Z ₂ , the unit vibration system Z ₁ has a higher Q value and the Helmholtz resonance system Z 2 becomes smaller. it becomes ₂ in low to reduce the volume of the cavity 5 (S _C becomes larger), the duct 6a, or long 6b, even kept constant resonance frequency of the Helmholtz resonance system Z ₂ and thin, The unit vibration system Z ₁ had a higher Q value and the resonance frequency, and the Helmholtz resonance system Z ₂ had a lower Q value. That is, since the output sound pressure frequency characteristics of the speaker system are closely related to the characteristics of the speaker unit 4, the volume of the cavity 5 and the dimensions of the ducts 6a and 6b, an advanced design technique is required to match them. Was needed. Further, even if they are perfectly matched, the reduction limit of uniform reproduction is at most the resonance frequency f _{OC when} the speaker unit 4 is mounted in the cavity 5. After matching, the cavity 5 can be miniaturized without losing output sound pressure characteristics, especially reduction characteristics, and the sound reproduction band of existing systems can be easily expanded without impairing characteristics such as sound quality. It is generally considered impossible to do. Also, the above Helmholtz resonance system Z ₂
The relationship between the frequency in the band lower than the resonance frequency f _OP and the resonant acoustic radiation ability is, when viewed from the sound pressure level, decreased at a rate of about 12 dB / oct with respect to the decrease in the frequency, and the resonance frequency is the bass reflex type. Alternatively, if it is set extremely low with respect to the basic idea of the speaker system with a resonator, it becomes extremely difficult to correct it by increasing or decreasing the input signal level.

As described above, the driving device of this embodiment is designed to drive the speaker system using Helmholtz resonance by negative impedance, so that the unit vibration system and the Helmholtz resonance system characteristics and dimensions can be independently set.
Moreover, even if the resonance frequency of the Helmholtz resonance system is set low, the Q value and bass reproduction ability can be kept high, and the unit drive system has a strong resonator drive ability (6d
B / oct), it is possible to obtain a characteristic that the waviness of the frequency characteristic can be corrected by increasing / decreasing the input signal level, for example, increasing / decreasing the normal sound quality adjustment degree. Further, as a result of the unit vibration system being substantially no resonance system, there is no abrupt phase change in the vicinity of the frequency f _OC , and the phase characteristics are good.
For this reason, the cavity 5 can be miniaturized without deteriorating the frequency characteristics and the sound quality, and the speaker system can be made compact, and the sound quality can be improved as compared with the conventional speaker system driven by a constant voltage, or the sound quality can be improved. It is possible to easily expand and drive the reproduction band, particularly the low-pitched sound side.

In the above description, only the case where Z _V −Z _O = 0 is described, but when Z _V −Z _O > 0, the characteristic values of the unit vibration system and the Helmholtz resonance system are
Depending on the value of Z _V -Z _O becomes a value between the case of the Z _V -Z _O = 0 if the conventional constant voltage drive system. Therefore, instead of positively utilizing this property, for example, the Q value of the Helmholtz resonance system is adjusted by adjusting the port diameter or inserting a mechanical Q damper such as glass wool or felt in the cavity 5. , it is possible to carry out by adjusting the negative impedance -Z _O.

FIG. 7 shows a basic configuration of a negative impedance generating circuit 8 for driving the vibrator (speaker unit) 4 with a negative impedance.

The circuit shown in the figure applies the output of the amplifier 81 having a gain A to the load Z _L by the vibrator 4. Then, the current flowing through the load Z _L I _L
Of the transmission gain β and the amplification circuit 81
Give positive feedback to. In this way, the output impedance Z _{O of the} circuit is obtained as Z _O = Z _S (1−Aβ) ... (2). If Aβ> 1 from this equation (2),
Z _O becomes the negative impedance of open stability. here,
Z _S is the impedance of the sensor that detects the current.

Therefore, in the circuit of FIG. 7, a desired negative impedance component can be included in the output impedance by appropriately selecting the type of impedance Z _S. For example, in the case of detecting the current I _L by the voltage across the impedance Z _S is the impedance Z _S is the resistance R _S
Then, the negative impedance component becomes a negative resistance component, the inductance L _S becomes a negative inductance component, and the capacitance C _S becomes a negative capacitance. Further, the integrator used in the feedback circuit 83, the impedance Z _S negative impedance component by detecting and integrating the voltage across the inductance L _S of the can is referred to as negative resistance component, further in the feedback circuit 83 using differentiator, negative impedance component be detected by differentiating the voltage across the capacitance C _S as the impedance Z _S becomes a negative resistance component. As the current detection sensor, it is possible to use a current probe such as a CT or a Hall element in addition to the impedance elements R _S , L _S , and C _S.

A concrete example corresponding to such a circuit is, for example, Japanese Patent Publication No. 59-
No. 51771 is shown.

It is also possible to detect the current on the non-grounded side of the vibrator 4. A concrete example of such a circuit is, for example, Japanese Patent Publication No.
-83704 and the like. FIG. 8 shows an example of BTL connection, but it is easy to apply it to the circuit of FIG. 8th
Reference numeral 84 in the figure is an inverting circuit.

FIG. 9 shows a specific circuit example of an amplifier including a negative resistance component in the output impedance.

The output impedance Z _O in the amplifier of FIG. 9 is Z _O = R _S (1-Rb / Ra) = 0.22 (1-30 / 1.6) = -3.9 (Ω).

[Other Embodiments] The present invention is not limited to the above embodiments,
It can be appropriately modified and implemented. For example, in the above-mentioned embodiment, the duct having the opening port is used as the acoustic mass means for constructing the resonator, but this may be a passive vibrating body such as a simple opening or a drone cone.

Further, in the above-described embodiment, the case where the negative impedance generating circuit is mainly used as the driving means has been described, but this driving means drives the vibrating body of the vibrator so as to cancel the reaction from the surroundings. As long as it is a so-called MFB as disclosed in JP-B-58-81156.
It may be a circuit.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a portable electric musical instrument according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of output sound pressure frequency characteristics of an audio device of the musical instrument of FIG. 1, and FIG. A front view showing a concrete application example of the portable electric musical instrument of FIG. 1, FIG. 4 is a sectional view taken along line II-II of the portable electric musical instrument of FIG. 3, and FIG. 5 is a sound of the musical instrument of FIG. An electrical equivalent circuit diagram of the device portion, FIG. 6 is an equivalent circuit diagram when Z _V −Z _O = 0 in FIG. 5, and FIG. 7 is a basic circuit diagram of a circuit that generates negative impedance, FIG. 8 is a circuit diagram showing a modified example of the circuit of FIG. 7, and FIG. 9 is a circuit diagram showing a specific example of the circuit of FIG. 1: Instrument housing 2: Sound generator (guitar strings) 3: Vibration plate 4: Vibrator (speaker unit) 5: Cavities 6a, 6b: Duct 7: Sound circuit (pickup) 8: Vibrator drive device 9a, 9b: Opening port

Claims (1)

[Claims] 1. A musical instrument main body having a resonator inside which is suitable for carrying, a sounding device for driving the resonator by generating mechanical vibration in response to a performance operation, and the mechanical vibration as an electric signal. In a portable electric musical instrument comprising a sounding circuit for converting and an acoustic device for converting the electric signal into sound and producing the sound, the acoustic device comprises the resonator or acoustic mass means arranged in the resonator. A resonator in which the resonance frequency is changed, and a vibrating body that forms a part of this resonator and drives this resonator on one surface while radiating sound from the other surface directly to the external region of the instrument body. A portable electric musical instrument comprising: a vibrating device having the vibrating device; and vibrating device driving means for driving the vibrating device so as to cancel the action of the vibrating body from the resonating device when the resonating device is driven.