JP4826775B2 - Speaker cabinet and speaker system design method - Google Patents

Description

The present invention relates to a speaker cabinet and a speaker system, and more particularly to a phase inversion cabinet for enhancing low sound that achieves both expansion of a low-frequency reproduction limit and flattening of frequency characteristics and a design method of a speaker system having the same.

  The speaker system includes a speaker unit and a cabinet (enclosure). As a cabinet to which the speaker unit is attached, a sealed type and a phase inversion type (bass reflex type) are known depending on the form and the like.

  In the phase inversion type, an opening (port) is mainly provided on a part of the unit mounting surface (baffle plate), and a pipe-shaped duct that forms a sound path is connected to the opening, or a duct is connected to the unit mounting surface. Molded integrally, reverses the phase of the sound wave radiated from the back of the unit through its duct, leads it to the front of the cabinet, and combines it with the sound wave radiated from the front of the unit to increase the efficiency of the low range Compared to the sealed type, there is an advantage that the sound pressure level in the low frequency band can be increased.

  As described above, the phase inversion type (bass reflex type) is used to improve the low frequency reproduction limit of the speaker system. However, if the resonance frequency of the duct is lowered to lower the reproduction limit, the sound pressure at the resonance point is reduced. When the volume of the cabinet is increased to reduce the sound pressure, the peak at the resonance point increases, and there is a problem that the expansion of the low frequency reproduction limit and the flattening of the frequency characteristics cannot be achieved simultaneously (see FIG. 14).

  On the other hand, as a phase inversion type modification, as shown in FIG. 15, the inside of the cabinet is divided into two chambers (air chambers 1C and 2C) communicated by a duct D1, and a unit SP is attached to one of the chambers and the other is a duct. There is known what is communicated with the outside by D2 (called double bass reflex). According to such a double bass reflex system, by setting the resonance point of the two ducts appropriately, the peak generated at the low frequency reproduction limit is controlled while using a large volume cabinet, and the frequency characteristic is relatively flat. However, a large dip occurs in the middle region as a price (see FIG. 16). This is essential for a double bass reflex that inevitably occurs regardless of cabinet volume or duct tuning.

  As another example, as shown in FIG. 17, speaker cabinets are composed of three air chambers 1C, 2C, and 3C that are stacked in a row. Of these, the speaker unit SP is placed in the uppermost air chamber 1C having the largest volume. The adjacent air chambers 1C, 2C and 2C, 3C communicate with each other through ducts D1, D2 (venting ports), and the uppermost and lowermost air chambers 1C, 3C communicate with the outside respectively. A bass reproduction speaker device having a configuration in which D4 (bass reflex port) is provided is known (for example, Patent Document 1).

JP 2003-169386 A

  However, according to Patent Document 1, since the first air chamber to which the speaker unit is attached communicates with the outside through the bass reflex port, it is difficult to expand the reproduction band (low frequency side).

  Further, Patent Document 1 only describes that the volume of the air chamber to which the speaker unit is attached is the maximum and the intermediate air chamber is the minimum, and the volume ratio and the resonance frequency of each duct (port) are described. There is no mention of the appropriate values related to sound, and the specific design method and optimization method are not clear, so that it is impossible to achieve both expansion of the low frequency range and flattening of the sound pressure frequency characteristics. there were.

  The present invention has been made in view of the circumstances as described above, and its purpose is to provide a phase inversion speaker cabinet and a cabinet for enhancing bass that achieve both expansion of the low frequency reproduction limit and flattening of frequency characteristics. It is providing the speaker system which has.

In order to achieve the above object, the present invention
The cabinet body 3A, the air chambers 31 to 3n (where n is an integer of 3 or more) formed by dividing the interior of the cabinet body 3A, and the ducts D1 to Dn− that sequentially connect the air chambers 31 to 3n. 1 and a duct Dn that communicates the air chamber n with the outside of the cabinet body 3A, and a speaker cabinet design method comprising :
When the resonance sharpness and the minimum resonance frequency of the speaker unit 2 attached to the air chamber 31 are Q ₀ and f ₀ , respectively, the sound pressure frequency characteristic obtained by driving the speaker unit 2 by the circuit simulator is −6 dB. and determining the cut-off frequency fc from the ratio of the cutoff frequency fc lowest resonance frequency f _0,
A step of both the resonant frequency of the duct 31~3n set in the range of 1.4Fc～4.2Fc,
Setting at least the actual volume Vcn of the air chamber 3n to at least twice the actual volume V _C1 of the air chamber 31;
From the gas chamber 31, to the gas chamber located on the most air chamber 31 side in the communication order of the air chamber having a 2-fold or more real volume of the actual volume V _C1, step of setting so that the actual volume is increased successively And
It is characterized by having .

The present invention also provides
The cabinet body 3A, the air chambers 31 to 3n (where n is an integer of 3 or more) formed by dividing the interior of the cabinet body 3A, and the ducts D1 to Dn− that sequentially connect the air chambers 31 to 3n. a duct Dn of the 1 and air chamber n communicates with the outside of the cabinet main body 3A, a speaker unit 2 mounted on the air chamber 31, a loudspeaker system design method with a
When the resonance sharpness and the minimum resonance frequency of the speaker unit 2 are Q ₀ and f ₀ , respectively, the cut-off frequency fc that is −6 dB in the sound pressure frequency characteristic obtained by driving the speaker unit 2 by the circuit simulator and the above-mentioned Obtaining the cut-off frequency fc from the ratio to the lowest resonance frequency f ₀ ;
The compliance equivalent volume of the speaker unit 2 is Vas, and the actual volume V _C1 of the air chamber 31 is in the range of 0.04 × Vas / (fc / f ₀ ) ^{2 to} 0.3 × Vas / (fc / f ₀ ) ² . Steps to set ,
A step of both the resonant frequency of the duct D1~Dn set in the range of 1.4Fc～4.2Fc,
Setting at least the actual volume Vcn of the air chamber 3n to at least twice the actual volume V _C1 of the air chamber 31;
From the gas chamber 31, to the gas chamber located on the most air chamber 31 side in the communication order of the air chamber having a 2-fold or more real volume of the actual volume V _C1, step of setting so that the actual volume is increased successively And
It is characterized by having .

The cabinet 3 includes a speaker unit 2 and a cabinet 3. The cabinet 3 has an air chamber 31 to which the speaker unit 2 is attached, an air chamber 32 communicated with the air chamber 31 via a duct D1, and the air chamber 32. A speaker system having a structure in which the air chamber 33 is provided with a duct D3 that communicates with the outside.
The compliance equivalent volume of the speaker unit 2 is Vas, the resonance sharpness of the speaker unit 2 is Q ₀ , the lowest resonance frequency of the speaker unit 2 is f ₀ , and the sound pressure frequency characteristic obtained by driving the speaker unit 2 is −6 dB cut-off frequency As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.3 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.3
Obtaining fc that satisfies the following condition :
By the following equation [Expression 1] including the fc as an operation section, the actual volume _{V C1} of the air chamber 31, the actual volume _{V C2} of the air chamber 32, the actual volume _{V C3} air chamber 33, the resonance frequency _f 1 of the duct D1, a step of calculating a resonant frequency _{f 3} of the resonance frequency _{f 2,} and the duct D3 ducts D2,
A method for designing a speaker system , comprising:
[Equation 1]
V _C1 = (0.15 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.20 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 = (0.075 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 2.5 × k ₄ × fc
f ₂ = 2.0 × k ₅ × fc
f ₃ = 1.9 × k ₆ × fc
[However, in the above formula, k _{1 to} k ₃ are real numbers of 0.5 to 2, and k _{4 to} k ₆ are real numbers of 0.7 to 1.4]
Furthermore, the speaker unit 2 and the cabinet 3 are comprised, and the interior of the cabinet 3 is an air chamber 31 to which the speaker unit 2 is attached, an air chamber 32 communicated with the air chamber 31 via a duct D1, and the air chamber 32. The air chamber 33 is connected to the air chamber 33 via the duct D2, and the air chamber 34 is connected to the air chamber 33 via the duct D3. The air chamber 34 is provided with a duct D4 that communicates with the outside. A speaker system design method comprising :
The compliance equivalent volume of the speaker unit 2 is Vas, the resonance sharpness of the speaker unit 2 is Q ₀ , the lowest resonance frequency of the speaker unit 2 is f ₀ , and the sound pressure frequency characteristic obtained by driving the speaker unit 2 is −6 dB cut-off frequency As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.25 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.25
Obtaining fc that satisfies the following condition :
By the following equation [Expression 2] including the fc as an operation section, the actual volume _{V C1} of the air chamber 31, the actual volume _{V C2} of the air chamber 32, the actual volume _{V C3} air chamber 33, the actual volume of the air chamber 34 _{V C4} a step of calculating the resonance frequency _{f 1,} the resonance frequency _{f 2} of the duct D2, the resonance frequency _{f 3} of the duct D3, and the resonance frequency _{f 4} of the duct D4 of the duct D1,
It is characterized by having .
[Equation 2]
V _C1 = (0.12 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.12 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 = (0.036 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C4 = (0.06 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
f ₁ = 2.8 × k ₅ × fc
f ₂ = 2.8 × k ₆ × fc
f ₃ = 2.8 × k ₇ × fc
f ₄ = 2.0 × k ₈ × fc
[However, in the above formula, k _{1 to} k ₄ are real numbers of 0.5 to 2, and k _{5 to} k ₈ are real numbers of 0.7 to 1.4]
The cabinet 3 includes a speaker unit 2 and a cabinet 3. The cabinet 3 has an air chamber 31 to which the speaker unit 2 is attached, an air chamber 32 communicated with the air chamber 31 via a duct D1, and the air chamber 32. An air chamber 33 communicated with the air chamber 33 via the duct D2, an air chamber 34 communicated with the air chamber 33 via the duct D3, and an air chamber 35 communicated with the air chamber 34 via the duct D4. A speaker system design method having a configuration in which a duct D5 that is divided and communicated to the outside is provided in the air chamber 35,
The compliance equivalent volume of the speaker unit 2 is Vas, the resonance sharpness of the speaker unit 2 is Q ₀ , the lowest resonance frequency of the speaker unit 2 is f ₀ , and the sound pressure frequency characteristic obtained by driving the speaker unit 2 is −6 dB cut-off frequency As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.2 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.2
Obtaining fc that satisfies the following condition :
By the following equation [Expression 3] containing the fc as an operation section, the actual volume _{V C1} of the air chamber 31, the actual volume _{V C2} of the air chamber 32, the actual volume _{V C3} air chamber 33, the actual volume of the air chamber 34 _{V C4} , the actual volume _{V C5} air chamber 35, the resonance frequency _{f 1} of the duct D1, the resonance frequency _{f 2} of the duct D2, the resonance frequency _{f 3} of the duct D3, the resonance frequency _{f 5} of the resonance frequency _{f 4,} and the duct D5 duct D4 A step of calculating
It is characterized by having .
[Equation 3]
V _C1 = (0.08 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.035 × k ₂ × Vas) / (fc / f ₀ ) ³ × Q ₀ ^0.5 )
V _C3 = (0.22 × k ₃ × Vas) / (fc / f ₀ ) ³
V _C4 = (0.045 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C5 = (0.055 × k ₅ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 3.0 × k ₆ × fc
f ₂ = 3.0 × k ₇ × fc
f ₃ = 2.5 × k ₈ × fc
f ₄ = 3.0 × k ₉ × fc
f ₅ = 2.3 × k ₁₀ × fc
[However, in the above formula, k _{1 to} k ₅ are real numbers of 0.5 to 2, and k _{6 to} k ₁₀ are real numbers of 0.7 to 1.4]

According to the present invention, the interior of the cabinet is divided into three or more air chambers, and each air chamber is connected to the series by a duct so that the resonance frequency of each duct is (1.4 to 4.2) At fc, the actual volume Vn of at least the most downstream air chamber is at least twice the actual volume V1 of the most upstream first air chamber, and the actual volume from the first air chamber Designed to increase the actual volume sequentially to the air chamber located closest to the first air chamber in the order of communication among the air chambers having an actual volume more than twice as large as V1, so that a normal bass reflex type etc. In comparison, a flat sound pressure frequency characteristic can be obtained while expanding the low frequency reproduction limit.

In particular, it is possible to resonance sharpness Q ₀ of the speaker unit to be _used, the lowest resonance frequency f _0, Hazuki group compliance equivalent volume Vas, and the actual volume of the air chambers, to obtain an appropriate value easily in the resonant frequency of each duct .

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 shows a configuration example of a speaker system according to the present invention. In FIG. 1, the speaker system 1 includes a speaker unit 2 and a cabinet 3 (enclosure). In particular, the cabinet 3 is divided into three chambers (air chambers 31, 32, 33) inside the cabinet body 3A forming the exterior. Among these, the speaker unit 2 is attached to the front surface of the air chamber 31, and the air chamber 31 and the air chamber 32 are communicated with each other by a duct D1 penetrating the partition wall therebetween. Further, the air chamber 32 and the air chamber 33 are communicated with each other by a duct D2 penetrating both partition walls, and the air chamber 33 is communicated to the outside by a duct D3 provided on the front surface thereof (hereinafter, such a mode is referred to as a triple bass reflex). ). In addition, the structure arrange | positioned outside the cabinet 3 may be sufficient as each duct D1-D3.

  Here, the concept itself of dividing the cabinet 3 into three air chambers 31 to 33 to form a triple bass reflex can be easily analogized as an extension of a bass reflex or a double bass reflex. Since the number of variables increases to six with the combination of the volume of 33 and the resonance frequency (duct tuning) of each of the ducts D1 to D3, it is difficult to obtain the optimum condition. It is not known at all whether the effect) can be obtained.

  Therefore, the present invention clarifies the design optimization conditions mainly for triple bass reflex through numerical simulation, and expands the low-frequency reproduction limit, flattens the sound pressure frequency characteristics, and further radiates bass sound through appropriate design. It is intended to improve efficiency.

Here, the minimum resonance frequency of the speaker unit 2 to be used is f ₀ [Hz], the compliance equivalent volume (vibration system equivalent conversion volume) is Vas [liter],
Actual volume of the air chamber 31 (V _C1 ) / Vas = V1
Actual volume of the air chamber 32 (V _C2 ) / Vas = V2
Actual volume of air chamber 33 (V _C3 ) / Vas = V3
Resonance frequency (f ₁ ) / f ₀ = fb1 of the duct D1
Resonance frequency (f ₂ ) / f ₀ = fb2 of the duct D2
Resonance frequency (f ₃ ) / f ₀ = fb3 of the duct D3
(The air chambers 32 and 33 have a plurality of ducts, so the actually observed resonance frequency is different from that of a single duct. The duct dimensions are set so that the resonance frequencies are f ₂ and f ₃ ).

FIG. 2 shows an acoustic equivalent circuit of a triple bass reflex speaker system. In FIG.
C1 is the compliance of the speaker unit,
L1 is the equivalent mass of the speaker unit,
R1 is a braking resistance of the speaker unit (R1 = 1 / Q ₀ ),
C2 is the compliance of the first air chamber 31 (C2 = V1),
L2 is an equivalent mass of the first duct D1 (L2 = 1 / (C2 × fb1 ² )),
C3 is the compliance of the second air chamber 32 (C3 = V2),
L3 is an equivalent mass of the second duct D2 (L3 = 1 / (C3 × fb2 ² )),
C4 is the compliance of the third air chamber 33 (C4 = V3),
L4 is an equivalent mass of the third duct D3 (L4 = 1 / C4 × fb3 ² )),
L5 is a sound pressure detection amount element (L5 = L1 / 1000).

Here, by normalizing the frequency axis at ω ₀ = 2πf ₀ , the actual volumes V _{C1 to} V _{C3 of the} air chambers to be changed according to the type of the speaker unit by the circuit simulator and the resonance frequencies f _{1 to} f _{3 of the} respective ducts. the Vas, can be calculated by generalizing the ratio of the f _0. When evaluating with a circuit simulator, the L5 is inserted into an equivalent circuit for sound pressure detection, and the frequency characteristic of the sound pressure is obtained from the voltage at both ends thereof.

  Note that what is obtained from the equivalent circuit shown in FIG. 2 is a theoretical value when the speaker unit and the duct are regarded as point sound sources and attached to an infinite plane baffle (2π space). In the characteristics, the characteristics change slightly due to the phase rotation due to the drop in the low frequency due to the diffusion of sound waves and the time lag due to the product of the length of the sound path and the speed of sound.

  In order to search for an optimum condition using a simulator including a circuit as shown in FIG. 2, the variables V1 to V3 and fb1 to fb3 defined as described above are individually changed, and a target sound pressure frequency characteristic is obtained by numerical simulation. If the deviation from the curve is evaluated and fine adjustment of each variable V1 to V3 and fb1 to fb3 is repeated little by little in the direction in which the deviation becomes smaller, the optimum value under the specified condition can be obtained. In order to compare the quality of the sound pressure frequency characteristic, the deviation from the target sound pressure frequency characteristic curve is obtained from the following equation.

Deviation (dB) = 10 × Log (Σ _{f = fmin to fmax} (Pt−P ₀ ) ² / N)
Here, Pt is the sound pressure level at the target frequency characteristic, P ₀ is the calculated output voltage (represented by a bold solid line in FIG. 3), N is the number of frequency sampling points, and f _min is the lowest value to be evaluated. The frequency, f _max, is the highest frequency to be evaluated.

FIG. 3 shows an evaluation example of the sound pressure frequency characteristic by the simulation as described above. As can be seen from FIG. 3, when the target sound pressure frequency characteristic is 0 dB flat, Pt is always 1, and f _min = 0.5 f ₀ , f _max = 8.0 f ₀ (evaluation width: 4 octaves). A _value of Q ₀ (resonance sharpness of the speaker unit, R1 = 1 / Q _{0 in} the circuit of FIG. 2) is set under each condition, and the variables V1 to V3 and fb1 to fb3 are automatically changed by a circuit simulator. Then, when searching for the condition that minimizes the deviation amount, the variables V1 to V3 and fb1 to fb3 converge to a certain value, and the optimum design value for the given Q ₀ and f _min and the minimum deviation amount under the condition. In addition, a ratio fr = fc / f ₀ of the −6 dB cutoff frequency fc and f ₀ of the sound pressure frequency characteristic is obtained. In FIG. 3, the hatched portion is the error amount, and its RMS (root mean square) is the deviation amount, which is about 1 dB.

In this way, as a result of evaluating the −6 dB cutoff frequency and the deviation amount when the values of Q ₀ and f _min are variously changed, the unit Q ₀ and the sound pressure frequency characteristic −6 dB cutoff frequency f It has been found that there is a close correlation between the ₀ ratio (fr = fc / f ₀ ) and the width of the frequency characteristic undulation (ripple) = deviation amount.

FIG. 4 shows the correlation between the unit Q ₀ value in the triple bass reflex method, the −6 dB cut-off frequency (f ₀ ratio), and the deviation amount, and FIG. 5 shows the case where the same simulation is performed with a normal bass reflex. The results are shown. As is clear from these figures, the deviation amount (ripple of frequency characteristics) is minimized when the resultant -6 dB cutoff frequency becomes a certain value with respect to Q _{0 of} the speaker unit, and the low frequency reproduction limit is reduced. Below this value, the deviation increases linearly. This tendency is almost the same for both a normal bass reflex and a triple bass reflex.

The amount of deviation depends on the -6 dB cut-off frequency and Q ₀ , but comparing the changes, the triple bass reflex has the same deviation amount 0.6 to 0.7 times on the frequency axis compared to the normal bass reflex. I understand that. From this, it can be said that the triple bass reflex can extend the low frequency reproduction limit to a frequency approximately 0.65 times that of a normal bass reflex while maintaining the same ripple amount (flatness) of the sound pressure frequency characteristics. Further, when the cutoff frequency is set to the same value, the flatness can be greatly improved. Note that the above 0.6 to 0.7 times, can be read by comparing each _{Q 0} curve of FIG. 4 and FIG. 5 shown in the following table 1.

図６に実際の設計例とその特性（Ｑ_０＝０．５のスピーカユニットを使用した数値シミュレーション結果）を示す。

FIG. 6 shows an actual design example and its characteristics (numerical simulation results using a speaker unit with Q ₀ = 0.5).

  In FIG. 6, the triple bass reflex is V1 = 0.79, V2 = 3.5, V3 = 3.9, fb1 = 1.23, fb2 = 0.91, fb3 = 0.89, and sealed. The type is V1 = 1.0, normal bass reflex V1 = 2.1, fb1 = 0.75, double bass reflex V1 = 1.1, V2 = 3.9, fb1 = 1.07, fb2 = 0.68 It is.

As apparent from FIG. 6, but the sound pressure frequency characteristic in the normal bass reflex becomes flat (as -3dB range) to 0.65 _{f 0} ratio, flat frequency characteristics up to approximately 0.45F ₀ is a triple bass reflex Can be maintained. Furthermore, sound waves in the double bass reflex but produce a large dip DP mid range when extending the low frequency reproduction limit to 0.5f _0, which is generated from the last duct communicating with the outside for the number of ducts is even (2) This is because the phase of the phase becomes opposite to that of the speaker unit near the high frequency limit and cancels each other. Incidentally, such a problem does not occur in a triple bass reflex with an odd number of ducts (three).

  Thus, in the triple bass reflex provided with three air chambers and three ducts communicating them in series, there is an effect that the low range can be expanded without causing a large dip in the mid range unlike the double bass reflex.

FIG. 7 shows the amplitude of the diaphragm in each system (normal bass reflex, double bass reflex, triple bass reflex 1) under the conditions shown in FIG. According to this, the amplitude of the triple bass reflex is slightly increased in the vicinity of 0.7 f ₀ , but it is suppressed to a level close to that of a normal bass reflex until 0.5 f _0, and can be handled with the same design as a normal bass reflex. I can say that.

  FIG. 8 shows the generated sound pressure per amplitude of the diaphragm. According to this, the efficiency improvement of 10 dB or more is observed in the triple bass reflex over a wide band as compared with the sealed type. This means that the diaphragm of the speaker unit needs only a small amplitude to generate the same sound pressure, and it can be said that the input resistance can be improved due to the amplitude limit. In addition, the efficiency improvement is particularly remarkable in a low frequency even when compared with a normal bass reflex, and it can be said that this is a system excellent in low-band radiation efficiency over a wide band.

As a specific example, actual measurement data in the case of using a full range unit with f ₀ = 90 Hz, Q ₀ = 0.47, and a diameter of 8 cm are shown in FIGS.

  As shown in FIG. 9, in the normal bass reflex, the low frequency range is lowered to lower the low frequency reproduction limit. However, the limit is still 65 Hz, whereas in the triple bass reflex, the low frequency sound pressure as shown in FIG. The low frequency reproduction limit is expanded to 50 Hz without lowering the level. Despite being a small speaker unit, the triple bass reflex has low distortion to the low range because the amplitude of the diaphragm is suppressed as described above, and when the low frequency is boosted and corrected by the amplifier. Such a sharp increase in distortion at low frequencies is not observed.

In parallel with the above analysis, the cabinet design values (V1, V2, V3, fb1, fb2, and fb3) with the smallest deviation from the flat characteristic are analyzed as correlations with the simulation conditions Q ₀ and f _min. As a result, it has been found that the optimum value of each variable can be described as a function of the -6 dB cutoff frequency ratio (fr = fc / f ₀ ) obtained instead of f _min .

The fact that the cabinet design value can be described by the cut-off frequency obtained after the design means that the cabinet can be designed by substituting the target low frequency reproduction limit frequency as fc. The obtained relational expression is shown below.
V1 = 0.15 / fr ²
V2 = (V1 × 4.0) / (3.0 × fr × Q 0 0.5) = 0.2 / (fr 3 × Q 0 0.5)
V3 = {(V1 × 0.5) / fr ² } / Q ₀ = 0.075 / (fr ⁴ × Q ₀ )
fb1 = 2.5 × fr
fb2 = 2.0 × fr
fb3 = 1.9 × fr
As apparent from the above equation, the value of V1 is inversely proportional to the square of the value of fr (fc / f ₀ ) regardless of Q _0, and the values of fb1 to fb3 have a constant ratio with fr (fc / f ₀ ). As a result, the values of V2 and V3 are several times the value of V1.

Note that fr is a ratio (fc / f ₀ ) between f _{0 of} the speaker unit to be used and a target low frequency reproduction limit frequency (−6 dB cut-off frequency fc of the sound pressure frequency characteristic), and fr = 0.2. can be set to 1.0, for the deviation between the flat characteristic enough to lower the relationship between Q ₀ (ripple frequency characteristic) is increased, the value of fr in consideration of the deviation amount allowed is set Should be. As described above, this value can be reduced to 0.6 to 0.7 times the normal bass reflex.

The actual volume (effective inner volume) V _{C1 to} V _C3 and the resonance frequencies f _{1 to} f ₃ of the air chambers and the resonance frequencies f _{1 to} f ₃ that are actually required when manufacturing the triple bass reflex speaker system are defined above. each was as Vas, given by the ratio of _{f 0.} In addition, each value can be adjusted within a certain range from the value given by the relational expression due to the required characteristics and total volume restrictions, etc. As a cabinet design condition, the triple bass reflex method is described by the following expression .
V _C1 [liter] = (0.15 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 [liter] = (0.20 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 [liter] = (0.075 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 2.5 × k ₄ × fc
f ₂ = 2.0 × k ₅ × fc
f ₃ = 1.9 × k ₆ × fc
[However, in the above formula, (fc / f ₀ ) = fr is (fc / f ₀ ) ≦ 0.3 / (Q ₀ +0.05), Q ₀ > 1 when Q ₀ ≦ 1.0. When _0.0 , (fc / f ₀ ) ≦ 0.3].

Note that k _{1 to} k ₃ are real numbers of 0.5 to 2, k _{4 to} k ₆ are real numbers of 0.7 to 1.4, and 1.0 is the most flat characteristic. Thus, it can be changed within a real number range of 0.5 to 2 and 0.7 to 1.4 according to required characteristics.

Then, according to the present invention, when fabricating a loudspeaker system 1 triple bass reflex, Vas, to f _0, the compliance equivalent volume of the loudspeaker unit to be used [l], and the lowest resonance frequency [Hz] were respectively substituted, fr = if fc / _{f 0} to assign a target value that the upper limit is determined by the _{Q 0,} the three real volume of the air chamber 31 to 33 constituting the cabinet [l], three resonance frequencies of the duct D1 to D3 [ Hz], and a speaker system manufactured based on this can obtain sound pressure frequency characteristics commensurate with the target fr.

  As described above, with the triple bass reflex method, it is possible to eliminate the mid-range dip that occurs in the double bass reflex, and to obtain the effect of expanding the low-frequency reproduction limit while obtaining a flat sound pressure frequency characteristic. As a result of performing the above analysis on a method in which the number of air chambers and ducts is increased from 3 to 4, 5, the low frequency reproduction limit (−6 dB cut-off frequency fc of the sound pressure frequency characteristic) is increased every time the number is increased. It has been found that the ripple of the frequency characteristic can be lowered while keeping substantially the same (see FIG. 11). In addition, it was found that the same rule as that of the triple bass reflex holds for the actual volume of the uppermost air chamber to which the speaker unit is attached and the resonance frequency of each duct.

In particular, the inside of the cabinet body 3A is divided into n (where n is an integer of 3 or more) air chambers 31 to 3n, and the air chambers 31 to 3n are sequentially connected by ducts D1 to Dn-1, and the communication is performed. When the air chamber 3n at one end side in the direction is communicated to the outside by the final duct Dn, and the speaker unit 2 is attached to the air chamber D1 at the other end side in the communicating direction, the speaker unit 2 attached to the air chamber 31 The resonance frequency of each of the ducts D1 to Dn is (1.4 to 4.2) × fc, and the actual volume of the most upstream air chamber 31 with the -6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving as fc. V _C1 is (0.04 to 0.3) × Vas / (fc / f ₀ ) ² , the most downstream air chamber has an actual volume Vcn that is at least twice that of V _C1 , and the actual air volume of each air chamber It is common that the volume increases sequentially from V _C1 Turned out to be a requirement.
However, if the actual volume upstream of the most downstream air chamber 3n are present twice or more air chambers V _C1, is more than twice the actual volume Vcn the most downstream air chamber is V _C1 at the downstream side As a prerequisite, the actual volume may be reduced, and it has been found that the desired acoustic characteristics can be obtained even in this case.

  Therefore, the present invention is not limited to the triple bass reflex type speaker system, and the inside of the cabinet 3 is divided into four air chambers 31 to 34 as shown in FIG. 12, and these are communicated in series with the four ducts D1 to D4. It is good also as a speaker system.

  Further, as shown in FIG. 13, the cabinet 3 may be divided into five air chambers 31 to 35, and the speaker system may be configured to communicate with the series through five ducts D1 to D5.

  In this way, by increasing the number of duct stages, the low frequency reproduction limit can be lowered more than triple bass reflex, and with 5 stages, the cut-off frequency is maintained while maintaining the same deviation up to about 0.5 times the normal bass reflex ratio. However, the effect is gradually reduced with increasing complexity of the cabinet structure. Theoretically, the number of stages can be increased as much as possible, and realistic effectiveness is well recognized up to about 5 stages.

In the speaker system having the structure shown in FIG. 12, the actual volumes V _{C1 to} V _{C4 of} the air chambers and the resonance frequencies f _{1 to} f ₄ of the ducts are set as follows by the same simulation as described above. The
V _C1 = (0.12 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.12 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 = (0.036 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C4 = (0.06 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
f ₁ = 2.8 × k ₅ × fc
f ₂ = 2.8 × k ₆ × fc
f ₃ = 2.8 × k ₇ × fc
f ₄ = 2.0 × k ₈ × fc
[Where, k _{1 to} k ₄ are real numbers of 0.5 to 2, k _{5 to} k ₈ are real numbers of 0.7 to 1.4, Vas is a compliance equivalent volume of the speaker unit, and Q ₀ is a speaker. The resonance sharpness of the unit, f ₀ is the lowest resonance frequency of the speaker unit, fc is the −6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving the speaker unit,
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.25 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.25].

In the speaker system having the structure shown in FIG. 13, the actual volumes V _{C1 to} V _{C5 of} the air chambers and the resonance frequencies f _{1 to} f ₅ of the ducts are set as follows by the same simulation as described above. The
V _C1 = (0.08 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.035 × k ₂ × Vas) / (fc / f ₀ ) ³ × Q ₀ ^0.5 )
V _C3 = (0.22 × k ₃ × Vas) / (fc / f ₀ ) ³
V _C4 = (0.045 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C5 = (0.055 × k ₅ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 3.0 × k ₆ × fc
f ₂ = 3.0 × k ₇ × fc
f ₃ = 2.5 × k ₈ × fc
f ₄ = 3.0 × k ₉ × fc
f ₅ = 2.3 × k ₁₀ × fc
[In the above equation, k _{1 to} k ₅ are real numbers of 0.5 to 2, k _{6 to} k ₁₀ are real numbers of 0.7 to 1.4, Vas is a compliance equivalent volume of the speaker unit, and Q ₀ is a speaker. The resonance sharpness of the unit, f ₀ is the lowest resonance frequency of the speaker unit, fc is the −6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving the speaker unit,
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.2 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.2].

  Although the present invention has been described above, the speaker system has a configuration in which the front of the unit is sealed with a cabinet and only the output of the final duct communicating with the outside is used (a system called a “Kelton type” for a normal bass reflex) However, as a result of the simulation, it was found that both the expansion of the low-frequency reproduction limit and the flattening of the sound pressure frequency characteristics can be achieved even with the multistage bass reflex speaker system of the same form.

Explanatory drawing which showed the example of a structure of the speaker system (triple bass reflex) which concerns on this invention Equivalent circuit diagram of triple bass reflex speaker Graph showing sound pressure frequency characteristics related to triple bass reflex speakers Correlation diagram of frequency and ripple amount in triple bass reflex speaker Correlation diagram of frequency and ripple amount in bass reflex speaker Comparison diagram showing sound pressure frequency characteristics of each type of speaker Comparison diagram showing the relationship between frequency and diaphragm amplitude for each type of speaker Comparison diagram showing the relationship between frequency and sound pressure level generated by diaphragm amplitude in each type of speaker Graph showing the sound pressure-distortion characteristics of bass reflex speakers Graph showing the sound pressure-distortion characteristics of a triple bass reflex speaker Comparison chart showing sound pressure frequency characteristics depending on the number of air chambers Explanatory drawing which shows the example of a change of the speaker system based on this invention Explanatory drawing which shows the example of a change of the speaker system based on this invention Graph showing frequency characteristics of bass reflex speaker Explanatory drawing showing a configuration example of a double bass reflex speaker Graph showing frequency characteristics of double bass reflex speaker Explanatory drawing which shows the other structural example of the conventional speaker.

DESCRIPTION OF SYMBOLS 1 Speaker system 2 Speaker unit 3 Cabinet 31 1st air chamber 32 2nd air chamber 33 3rd air chamber 34 4th air chamber 35 5th air chamber D1 1st duct D2 2nd duct D3 3rd duct D4 4th duct D5 Fifth duct V _C1 Actual volume of the first air chamber V _C2 Actual volume of the second air chamber V _C3 Actual volume of the third air chamber V _C4 Actual volume of the fourth air chamber V _C5 Actual volume of the fifth air chamber f ₁ Resonance frequency of the first duct f ₂ resonance frequency of the second duct f ₃ resonance frequency of the third duct f ₄ resonance frequency of the fourth duct f ₅ resonance frequency of the fifth duct Q ₀ resonance sharpness of the speaker unit f ₀ speaker unit Minimum resonance frequency of Vas Compliance equivalent volume of speaker unit fc -6 dB cutoff frequency of sound pressure frequency characteristic fr fc / f ₀

Claims (5)

A cabinet main body, a first air chamber to an nth air chamber (where n is an integer of 3 or more) formed by dividing the interior of the cabinet main body, and a first duct to an nth air passage that sequentially communicates each air chamber. A speaker cabinet having a -1 duct and an nth duct communicating with the outside of the cabinet body,
When the resonance sharpness and the minimum resonance frequency of the speaker unit attached to the first air chamber are Q ₀ and f ₀ , respectively, the sound pressure frequency characteristic obtained by driving the speaker unit by the circuit simulator is −6 dB. Obtaining the cut-off frequency fc from the ratio of the cut-off frequency fc to the lowest resonance frequency f ₀ ,
And setting the range of 1.4fc~4.2fc both the resonance frequency of the first to n duct,
Setting a real volume Vcn of at least the first n air chamber more than twice the first air chamber of the real volume V _C1,
From the first gas chamber until air chamber located closest to the first air chamber side communicating the order of the air chamber having a 2-fold or more real volume of the actual volume V _C1, so that the actual volume is increased successively Steps to set ,
Speaker cabinet design method characterized in that it comprises a. A cabinet main body, a first air chamber to an nth air chamber (where n is an integer of 3 or more) formed by dividing the interior of the cabinet main body, and a first duct to an nth air passage that sequentially communicates each air chamber. A speaker system design method comprising: an nth duct that communicates a duct and an nth air chamber with the outside of the cabinet body; and a speaker unit attached to the first air chamber,
When the resonance sharpness and the minimum resonance frequency of the speaker unit are Q ₀ and f ₀ , respectively , a cutoff frequency fc that is −6 dB in the sound pressure frequency characteristic obtained by driving the speaker unit by the circuit simulator, and the Obtaining the cut-off frequency fc from the ratio to the lowest resonance frequency f ₀ ;
The compliance equivalent volume of the speaker unit is Vas, and the actual volume V _C1 of the first air chamber is 0.04 × Vas / (fc / f ₀ ) ^{2 to} 0.3 × Vas / (fc / f ₀ ) ² . A step to set the range;
And setting the range of 1.4fc~4.2fc both the resonance frequency of the first to n duct,
Setting a real volume Vcn of at least the first n air chamber more than twice the first air chamber of the real volume V _C1,
From the first gas chamber until air chamber located closest to the first air chamber side communicating the order of the air chamber having a 2-fold or more real volume of the actual volume V _C1, so that the actual volume is increased successively Steps to set ,
Speaker cabinet design method characterized in that it comprises a. The cabinet comprises a speaker unit and a cabinet, and the cabinet has a first air chamber to which the speaker unit is attached, a second air chamber communicated with the first air chamber via a first duct, and the second air chamber. A design method of a speaker system configured to be divided into a third air chamber communicated with a chamber through a second duct, and to be provided with a third duct that communicates with the third air chamber;
The compliance equivalent volume of the speaker unit is Vas, the resonance sharpness of the speaker unit is Q ₀ , the lowest resonance frequency of the speaker unit is f ₀ , and the −6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving the speaker unit As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.3 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.3
Obtaining fc that satisfies the following condition :
Wherein the following equation [Expression 1] including fc as calculation term, said first air chamber of the real volume V _C1, the second real volume of the air chamber V _C2, the third air chamber of the real volume V _C3, the first the resonance frequency f ₁ of the first _duct, and a step of calculating a resonant frequency f _2, and the resonance frequency f ₃ of the third duct of said second duct,
A method for designing a speaker system , comprising:
[Equation 1]
V _C1 = (0.15 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.20 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 = (0.075 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 2.5 × k ₄ × fc
f ₂ = 2.0 × k ₅ × fc
f ₃ = 1.9 × k ₆ × fc
[However, in the above formula, k _{1 to} k ₃ are real numbers of 0.5 to 2, and k _{4 to} k ₆ are real numbers of 0.7 to 1.4] The cabinet comprises a speaker unit and a cabinet, and the cabinet has a first air chamber to which the speaker unit is attached, a second air chamber communicated with the first air chamber via a first duct, and the second air chamber. A third air chamber communicated with the chamber via the second duct and a fourth air chamber communicated with the third air chamber via the third duct are separated into the fourth air chamber and communicated to the outside. A speaker system design method having a configuration in which a fourth duct is provided,
The compliance equivalent volume of the speaker unit is Vas, the resonance sharpness of the speaker unit is Q ₀ , the lowest resonance frequency of the speaker unit is f ₀ , and the −6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving the speaker unit As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.25 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.25
Obtaining fc that satisfies the following condition :
According to the following formula [Equation 2] including the fc as an operation term, the actual volume V _C1 of the first air chamber, the actual volume V _{C2 of} the second air chamber, the actual volume V _{C3 of} the third air chamber, Calculating an actual volume V _C4 , a resonance frequency f ₁ of the first duct, a resonance frequency f _{2 of} the second duct, a resonance frequency f ₃ of the third duct , and a resonance frequency f ₄ of the fourth duct ;
A method for designing a speaker system , comprising:
[Equation 2]
V _C1 = (0.12 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.12 × k ₂ × Vas) / {(fc / f ₀ ) ³ × Q ₀ ^0.5 }
V _C3 = (0.036 × k ₃ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C4 = (0.06 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
f ₁ = 2.8 × k ₅ × fc
f ₂ = 2.8 × k ₆ × fc
f ₃ = 2.8 × k ₇ × fc
f ₄ = 2.0 × k ₈ × fc
[However, in the above formula, k _{1 to} k ₄ are real numbers of 0.5 to 2, and k _{5 to} k ₈ are real numbers of 0.7 to 1.4] The cabinet comprises a speaker unit and a cabinet, and the cabinet has a first air chamber to which the speaker unit is attached, a second air chamber communicated with the first air chamber via a first duct, and the second air chamber. A third air chamber communicated with the chamber via the second duct, a fourth air chamber communicated with the third air chamber via the third duct, and a fourth duct connected to the fourth air chamber via the fourth duct. A method for designing a speaker system that is divided into a fifth air chamber that communicates with the fifth air chamber and that includes a fifth duct that communicates with the fifth air chamber.
The compliance equivalent volume of the speaker unit is Vas, the resonance sharpness of the speaker unit is Q ₀ , the lowest resonance frequency of the speaker unit is f ₀ , and the −6 dB cutoff frequency of the sound pressure frequency characteristic obtained by driving the speaker unit As fc
When Q ₀ ≦ 1.0, (fc / f ₀ ) ≦ 0.2 / (Q ₀ +0.05),
When Q ₀ > 1.0, (fc / f ₀ ) ≦ 0.2
Obtaining fc that satisfies the following condition :
According to the following formula [3] including the fc as an operation term, the actual volume V _C1 of the first air chamber, the actual volume V _{C2 of} the second air chamber, the actual volume V _{C3 of} the third air chamber, The actual volume V _C4 , the actual volume V _C5 of the fifth air chamber, the resonance frequency f ₁ of the first duct, the resonance frequency f _{2 of} the second duct, the resonance frequency f ₃ of the _third duct, and the resonance frequency f _{4 of} the fourth duct. And calculating the resonance frequency f ₅ of the fifth duct ;
A method for designing a speaker system , comprising:
[Equation 3]
V _C1 = (0.08 × k ₁ × Vas) / (fc / f ₀ ) ²
V _C2 = (0.035 × k ₂ × Vas) / (fc / f ₀ ) ³ × Q ₀ ^0.5 )
V _C3 = (0.22 × k ₃ × Vas) / (fc / f ₀ ) ³
V _C4 = (0.045 × k ₄ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ }
V _C5 = (0.055 × k ₅ × Vas) / {(fc / f ₀ ) ⁴ × Q ₀ )
f ₁ = 3.0 × k ₆ × fc
f ₂ = 3.0 × k ₇ × fc
f ₃ = 2.5 × k ₈ × fc
f ₄ = 3.0 × k ₉ × fc
f ₅ = 2.3 × k ₁₀ × fc
[However, in the above formula, k _{1 to} k ₅ are real numbers of 0.5 to 2, and k _{6 to} k ₁₀ are real numbers of 0.7 to 1.4]

Images