JP2000069582A - Speaker system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To emit only a sound pressure with a frequency in resonance with a low frequency of a duct of the phase inversion type speaker system. SOLUTION: A movable baffle board 25 that is freely movable with a flexible part 24 having a sprint constant of K is formed for a baffle board 2 of a speaker box 1, a speaker 3 is placed on the movable baffle board 25 and a resonance frequency from the speaker 3 in the vicinity of a low resonance frequency of a duct 18 is cancelled or attenuated by using a resonance frequency of the movable baffle board 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small and lightweight speaker device, and more particularly to a bass reflex type (phase inversion type).
The present invention relates to improvement of a speaker device.

[0002]

2. Description of the Related Art Conventionally, as an effective means for extending the low-frequency reproduction limit of a speaker device, for example, an opening and a duct are provided in a baffle plate provided with a speaker, and a phase of a sound emitted from a back surface of a diaphragm of the speaker is adjusted. A phase inversion type loudspeaker device that inverts and radiates outside through an opening through a duct to enhance the sound wave emitted from the diaphragm of the loudspeaker to the front so as not to distort the bass range is well known.

[0003] Such a phase inversion type speaker device is shown in FIG.
As shown in FIG. 1A, a speaker 3 is fixed so as to face a speaker sound emission hole 2a formed in a baffle board 2 provided on a front surface of a speaker box 1.

As shown in FIG. 4A, for example, the speaker 3 is provided with a ring-shaped magnet 4, a plate 5 and a yoke 6 attached so as to sandwich the ring-shaped magnet 4, and an inner periphery of the plate 5. A magnetic gap 7 is formed between the side and the center pole 6a of the yoke 6. A frame 8 of the speaker 3 is mounted on the plate 5, and an edge 9 is provided on an outer peripheral portion of the frame 8, and the outer peripheral portion of the cone-shaped diaphragm 10 is held by the edge 9.

On the other hand, a voice coil bobbin 11 is mounted on the inner peripheral portion of the diaphragm 10, and a voice coil 12 is wound around the voice coil bobbin 11, and the voice coil 12 is fixed by a center pole 6a of the plate 5 and the yoke 6. It is designed to be inserted into the formed magnetic gap 7. Reference numeral 17 denotes a damper for holding the voice coil 12 in the magnetic gap 7.

An acoustic signal from an input terminal 13a provided at a predetermined position outside the speaker box 1 is connected to a connection line 1
4a to the terminal 15 of the speaker 3 via the terminal 15a.
Of the voice coil 12 via the tinsel wire 16
To supply.

A duct 18 having an opening 18a on the same surface as the speaker sound emission hole 2a of the baffle board 2 is provided.
The phase of the sound emitted from the rear surface of the diaphragm 10 of the speaker 3 is inverted and radiated from the duct 18 to the outside of the speaker box 1, thereby widening the bass range of the sound coming out of the front surface of the diaphragm 10.

As described above, an electrical equivalent circuit of the phase inversion type speaker device can be represented as shown in FIG.

In FIGS. 4A and 4B, S ₀ is the stiffness of the support system of the speaker 3, M ₀ is the equivalent mass of the support system of the speaker 3, R _ms0 is the mechanical resistance of the speaker support system,
_m0 is the mechanical resistance of the air loading of the speaker, R ₀ is expressed by R _m0 + R _ms0 = R ₀ equivalent mechanical resistance of the speaker. S _C is the stiffness of the speaker box 1, R ₀ is the mechanical resistance of the air loading of the duct 18 portions, M _D is the air mass in the duct 18 portions.

By using the above-described speaker device, the bass reproduction limit frequency is lower than the closed type by 1 / √3 compared to the bass resonance frequency when placed in a closed type speaker box 1 having the same volume. It is said that can be expanded.

FIG. 5 shows a bass reproduction limit frequency characteristic curve of a speaker device having such a phase inversion type speaker box.

In FIG. 5, the horizontal axis represents frequency (Hz), and the vertical axis represents sound pressure response (dB) and impedance (Ω). A curve 19 indicated by a dashed line represents a curve near the low-band resonance frequency of the speaker 3. A sound pressure-frequency characteristic, similarly, a curve 20 indicated by a broken line is a sound pressure-frequency characteristic near the low-band resonance frequency of the duct 18, and a curve 21 indicated by a solid line is the speaker 3 and the duct 18.
Combined sound pressure-frequency characteristics, curve 22 indicated by a two-dot chain line
Is an impedance characteristic.

The above-mentioned sound pressure-frequency characteristic curves 19 to 22
It can be seen that the speaker 3 is
It can be understood that the bass reproduction band can be expanded by disposing the.

[0014]

As described above, in the loudspeaker apparatus of the phase inversion type, the low-frequency reproduction band can be expanded by 1 / √2 to 1 / √3 times the low-frequency reproduction band as compared with the plane baffle or the closed type. However, as can be seen from the sound pressure-frequency characteristic curve of FIG. 5, the overall characteristic 21 which is the sum of the characteristic curve 19 of the speaker 3 and the characteristic curve of the duct 18 is as follows.
The low-frequency reproduction can be expanded only up to approximately the middle position of the valley 2, and in the low frequency range indicated by the oblique line 23 in FIG. 5 below this valley, the sound radiation direction of the speaker 3 and the sound radiation direction of the duct 18. Are reversed, so that the sound pressures cancel each other out. That is, regardless of whether the sound in this band is radiated from the speaker 3 and the duct 18, there is a problem that the sound pressure is canceled out and cannot contribute to the expansion of low-frequency reproduction.

The present invention has been made in order to solve the above-mentioned problems, and an object to be solved by the present invention is to eliminate the noise canceling pressure indicated by the above-mentioned oblique line 23 and to reduce the vicinity of the low-band resonance frequency of the duct. Speaker 3 so as not to cancel the sound pressure of
The sound pressure in the vicinity of the low-band resonance frequency of the duct 18 is not output from the vicinity, and the sound pressure in the vicinity of the low-band resonance frequency of the duct 18 is output so that reproduction in the low band is expanded.

[0016]

A speaker device according to the present invention is a speaker device in which a speaker and a duct for phase inversion are arranged on a baffle board in a speaker box. The sound pressure near the frequency is removed.

According to the speaker device of the present invention, it is possible to reproduce the low range up to the vicinity of the resonance frequency of the duct used in the phase inversion type speaker box, and to obtain a low range reproduction that can be greatly expanded.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a speaker device according to the present invention.
An embodiment will be described with reference to FIGS. FIG.
The parts corresponding to those of the speaker device shown in FIG.

The speaker 3 used in FIG. 1 has exactly the same structure as that described in detail with reference to FIG.

In a speaker box 1 for constituting a phase inversion type speaker device, a duct opening 18a is formed below the baffle board 2 as in FIG. It is formed integrally with the baffle board 2 using a synthetic resin such as ABS so as to extend.

In this embodiment, a flexible portion 24 is formed on the baffle board 2, and the speaker 3 is attached to a speaker sound emission hole 2a formed in a movable baffle board 25 surrounded by the flexible portion 24. .

The position of the flexible portion 24 shown in FIG.
From the center of the vibration plate 10 of a predetermined diameter. FIG. 2A shows a front view of the baffle board 2 of FIG. 1 as viewed from the front. In this case, the flexible portion 24 has a substantially square shape, and the movable baffle board 25 is also rectangular.

FIG. 2B shows a case where a circular flexible portion 24 and a movable baffle board 25 are formed around the speaker 3.

FIG. 2C shows a case where the flexible portion 24a and the movable baffle board duct 25a are formed in a circular shape so as to surround the opening 18a of the duct 18. In this case, the resonance frequency of the duct 18 is designed. It will be easier.

FIG. 2D shows that the flexible portion 24 and the movable baffle board 25 are formed in a rectangular shape.
5 shows a case where the speaker 3 and the duct 18 are disposed in the interior of the vehicle.

When the baffle board is formed, the flexible portion 24 may be corrugated as shown in the side sectional view of FIG.
As shown in (H), the free edge of the diaphragm 10 at the time of making the speaker or the edge of the synthetic resin or the like having a waveform is formed into a circular or square shape like the damper for holding the diaphragm 10, and the speaker is attached to the baffle board 2. 3 is formed in a circular or square notch 26 so as to surround the movable baffle board 25 to which the
As shown in FIGS. 2 (E) and 2 (F), the circular or square edge-shaped mountain-like flexible portions 24b and 24c are joined to the baffle board 2 with an adhesive as shown in FIGS. Can be swingable.

FIG. 2E shows a state where the top of the ridge of the flexible portion 24b is attached to the front side, and FIG. 2F shows a state where the top of the ridge is attached to the rear side (the inside of the baffle board 1). Is the case.

Further, in the case of FIGS. 2G and 2H, the circular or square flexible portions 24d and 24e having the same structure as the damper are provided with the corrugated peaks and valleys opposite from the inside of the cut groove 26. This is the case where they are joined together.

The operation of the speaker device of the present invention having the above-described configuration will be described below with reference to FIGS.

Assuming that the equivalent mass of the vibration system of the speaker 3 in FIG. 1 is M ₀ as in FIG. 4 and the acceleration applied to the vibration system of the speaker 3 is α ₀ , the vibration system is fixed to the movable baffle board 25 in the speaker box 1. When the speaker 3 is driven, the sound radiation force from the diaphragm 10 can be expressed as F ₁ = M ₀ · α ₀ .

The reaction force -F = M ₀ · α _{0 to} the sound radiation force F ₁ of the speaker 3 naturally occurs.

Now, assuming that the equivalent mass of the movable baffle board 25 in FIG. 1 is M _{1 and} the equivalent mass (self-weight) of the M ₁ speaker 3 is M _S , the movable baffle board 25 and the speaker 3 are integrated and one The equivalent mass M ₂ of the movable baffle board 25 including the speaker 3 is M ₂
= M ₁ + M _S. The acceleration applied to the movable baffle board 25 including the speaker 3 is α ₂ , and the flexible portion 2
Assuming that the compliance (spring constant) of the speaker 4 is K, the movable baffle board 25 including the speaker 3 applies a sound radiation force F ₁ = M ₀ · α ₀ when the speaker 3 is driven to the diaphragm 10 of the speaker 3. The movable baffle board 25 receives the acting force of F ₂ = M ₂ · α ₂ with the reaction force at the time of acting −F ₁ as the exciting force. In this case, it can be expressed as F ₂ ≒ −F ₁ .

In this case, the resonance frequency f ₀₂ of the movable baffle board 25 including the loudspeaker 3 is obtained by the following equation (1).

[0034]

On the other hand, the resonance frequency f _0D of the duct 18 is shown in FIG.
If the equivalent mass of the duct 18 is M _D and the compliance of the duct is S _D , as in A, it can be obtained by equation (2).

[0036]

In this embodiment, the resonance frequencies f ₀₂ and f _0D of the above-mentioned equations (1) and (2) can be selected so that f ₀₂ ≦ f _0D .

Assuming that the area of the diaphragm 10 of the speaker 3 is S and the area of the movable baffle board 25 is S _K as shown in the schematic diagram of FIG. 3A, F ₁ = α ₀ · M _0. ≒ F ₂
= M ₂ · α _2, the acceleration α ₂ of the movable baffle board 25 including the speaker 3 can be expressed by the following equation (3).

[0039]

Therefore, the displacement that the speaker 3 receives at the acceleration α ₀ is X ₁ , and the movable baffle board 25 including the speaker 3
Is the acceleration α ₀ of the reaction force of the sound radiation force of the speaker 3 −F _1.
If the displacement receiving and X ₂ as excitation force, displacement X ₂ of the movable baffle board 25 containing the speaker 3 (3)
From the equation, it can be expressed by the following equation (4).

[0041]

Accordingly, the relationship between the sound pressure S · X ₁ of the speaker 3 and the sound pressure (S _K −S) · X _{2 in} which the movable baffle board 25 including the speaker 3 moves in the opposite direction is expressed by the following equation (5). Assuming that S · X ₁ ≒ (S _K −S) · X ₂ ‥‥ (5), when the resonance frequency of f ₀₂ = f _0D , when the speaker 3 moves backward due to the reaction force −F ₁ of the speaker 3 Offset or attenuated by the sound pressure F ₁ ≒ F ₂ = M ₂ · α ₂ ,
By making the sound pressure of the speaker 3 apparently approach zero,
The sound pressure at the time of resonance f _{0D of the} duct 18 is changed to the resonance f _{02 of the} speaker 3.
The sound pressure at the time does not cancel out like the area 23 in FIG.
Since only the low-band resonance frequency of the duct 18 can be radiated and the low band can be expanded to the resonance frequency f _0D or less of the duct 18, for example, the low band of the overall frequency characteristic is The low frequency band can be expanded up to the rising portion of the low frequency resonance frequency of 18.

The area S _K of the movable baffle board 25 can be easily obtained from the following equation (6) from the equation (5).

[0044]

From the equation (6), the smaller the equivalent mass M ₂ of the movable baffle board 25 including the speaker 3, the smaller the area S _K of the movable baffle board 25 can be.

[0046] Incidentally, if move actually the equivalent mass M ₂ is the acceleration alpha ₂ movable baffle board 25 including a speaker 3, the inertia force M ₂ · alpha ₂ acts, (5), the M ₂ · α
_Since (S _K -S) · X ₂ generated by the inertial force of ₂ must be added, the equation (5) can be expressed as the following equation (7).

S ・ X ₁ ≒ (S _K -S) ・ X ₂ + (S _K -S) ・ X ₂ ‥‥ (7)

[0048] From equation (8). From these, the area S _K of the movable baffle board 25 may be halved as compared with the equation (6).

Under the above conditions, the sound pressure of sound emitted from the speaker 3 at a frequency near f ₀₂ ≒ f _0D becomes very weak, and only the sound pressure due to the low-band resonance frequency f _0D of the duct 18 remains. The sound pressure at the low-band resonance frequency f _0D is emphasized and radiated from the duct 18, and a comprehensive frequency characteristic curve can be obtained in which the low-frequency range can be expanded even with a small and lightweight speaker device.

Now, when the case where the speaker 3 having a diameter of 65 mm is put in the speaker box 1 having a capacity of 1 liter is calculated, the movable part dimension of the movable baffle board 25 of the speaker box 1 is 13 cm × 28 cm, and the depth is 2.8.
cm and a very small speaker box shape. In the present invention, the area of the baffle board 2 cannot be made very small, but the depth can be made very thin, and a speaker device with an expanded low range can be provided.

As can be seen from FIG. 5, the sound pressures near the low-band resonance frequency of the speaker 3 and the duct 18 are opposite to each other in the speaker 3 and the duct 18, but the wavelength is very long in the low band. Therefore, there is no particular problem in the low-frequency radiation.

As described above, the present invention enables sound pressure reproduction in which the reproduction band is extended to a low frequency range of the resonance frequency of the duct, as compared with a conventional conventional phase inversion type speaker device. That is,
The sound in the band near the resonance frequency of the duct 18 from the speaker 3 is canceled by the movable baffle board 25 that moves in the direction opposite to the movement of the diaphragm 10 of the speaker 3, and the resonance of the duct 18 in the band below the resonance frequency of the duct 18. Only sound pressure can be radiated.

As shown in FIG. 3B, the electrical equivalent circuit of the movable baffle board 25 has an equivalent mass M ₂ = M ₁ + M _{S of the} movable baffle board 25 including the speaker 3, a compliance K of the flexible portion, and A radiation resistance R _R and a radiation mass M _R, which are radiation impedances of the movable baffle board 25, are connected in series to a voltage source F _V01 which uses a reaction force −F ₁ generated by the sound radiation force of the speaker 3 as an excitation force, and is a band-pass filter. since constitute a resonance sharpness Q of this circuit, neglecting M _R so large M ₂ compared to M _R, Q = omega ₀ · M ₂ /
Since it can be represented by R _R , Q can be selected to be large by reducing the mechanical equivalent resistance of the movable baffle board 25, and the resonance sound pressure of the low-band resonance frequency curve 20 of the duct 18 can be sharpened.

Although an example has been described above in which the depth of the speaker box 1 can be made extremely thin, if the thickness is increased, the volume of the speaker box 1 is further increased.
This makes it possible to further expand the low-frequency reproduction band region.

In the above embodiment, the diaphragm 10 of the speaker 3
Although but it does not consider the sound pressure changes in the speaker box 1 when it is driven by the sound radiation force F _1, the case where consideration of these will be discussed.

Now, when the diaphragm 10 of which the area of the speaker 3 is S is driven to move by X ₁ as shown in FIG. 3A, a pressure change of S · X ₁ occurs in the speaker box 1.

Since the area of the movable baffle board 25 disposed so as to surround the speaker 3 is S _K -S,
The displacement of the movable baffle board 25 caused by the pressure change in the speaker box 1 when the speaker 3 is driven is represented by X ₃
Movable baffle board 2 S · X ₁ as an excitation force if
No. 5 is given a displacement of (S _K -S) · X ₃ .

In this case, if the radiation force of the movable baffle board 25 by the excitation force F ₁ is F ₃ , F ₃ = F ₁ and (S _K −S) · X ₃ = S · X _1. . However,
If only the vicinity of the low-band resonance frequency of the duct 18 is set, and if the Q of the movable baffle board 25 is set to be larger than the low-band resonance frequency, the movable baffle board 25 may be considered as a rigid body.

Accordingly, the displacement X ₃ of the movable baffle board 25 due to the volume change can be expressed by the following equation (9).

[0060]

The movable baffle board 25 is displaced by the reaction force F ₁ of the sound radiation force F ₁ of the speaker 3 (S _K −
And S) · X _2, the displacement caused by the inertia force of the movable baffle board _{25 (S K -S) · X} 2 and (9) displaced by the pressure change in the speaker box 1 of Formula (S _K -S) · X
It will move by the amount of adding ₃ .

Therefore, the displacement X _{0 in} the F ₂ direction of the movable baffle board 25 in consideration of the inertial force when the speaker 3 is driven in the F ₁ direction and the pressure change of the speaker box is given by the following (1)
0)

X ₀ = (S _K −S) · X ₂ + (S _K −S) · X ₂ + (S _K −S) · X ₃ ‥‥ (10)

[0064] on (10) first term displacement amount of the F ₂ direction movable baffle board 25 by reaction force -F ₁ sound radiation force F ₁ of the speaker 3 in formula, the second term is movable baffle board 25 Is the displacement due to the sound radiation sound pressure due to the inertial force caused by the large equivalent mass of the above, and the third term is the displacement due to the pressure fluctuation in the speaker box 1.

The equation (10) is Is obtained as in equation (11).

The equation (11) and the above equation (8) are the same, but in the equation (11), the movable baffle board 25 moves extra by X ₂ + X ₃ , and in the case of S _K0 , the amount corresponding X _3, further comprising the manner it is possible to miniaturize the speaker box 1.

[0067]

According to the speaker device of the present invention, the low-frequency reproduction region can be expanded to the lowest resonance frequency portion of the duct as compared with a normal phase inversion type speaker device, and resonance at a frequency near the resonance frequency of the duct can be achieved. A speaker device that can increase the sharpness Q, increase the low-range sound pressure, and extremely reduce the depth of the speaker box can be obtained.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a speaker device of the present invention.

FIG. 2 is an explanatory diagram of a movable baffle board used in the speaker device of the present invention.

FIG. 3 is an electrical equivalent circuit and a schematic diagram of a movable baffle board used in the speaker device of the present invention.

FIG. 4 is a sectional view and an electrical equivalent circuit diagram of a conventional speaker device.

FIG. 5 is an explanatory diagram of a conventional low-frequency characteristic.

[Explanation of symbols]

1 ‥‥ speaker box, 2 ‥‥ baffle board, 3 ‥
‥ Speaker, 18 ‥‥ duct, 24 ‥‥ flexible part, 25 ‥
‥ Movable baffle board

Claims (4)

[Claims] 1. A speaker device in which a speaker and a phase inversion duct are disposed on a baffle board in a speaker box, wherein a sound pressure in a vicinity of a low-band resonance frequency of the speaker and in a vicinity of a resonance frequency of the duct is removed. A speaker device characterized by the following. 2. The speaker is disposed on a movable baffle board having an edge-shaped flexible portion formed on the baffle board, and the resonance frequency of the speaker and the movable baffle board in the flexible portion is set to the resonance frequency of the duct. 2. The speaker device according to claim 1, wherein said speaker device is selected to be substantially equal to or less than a resonance frequency of said duct. 3. The movable baffle board, wherein the speaker is disposed on a movable baffle board having an edge-shaped flexible portion formed integrally with the baffle board, and the movable baffle board is driven by a reaction force of sound radiation of the speaker. The speaker device according to claim 1 or 2, wherein: 4. A speaker box including a movable baffle board in which an edge-shaped flexible portion is formed integrally with the baffle board, wherein the speaker is disposed, and a change in sound pressure in the speaker box when the speaker emits sound. 2. The movable baffle board is driven by means of
Or the speaker device according to claim 2.