JP2001157290A - Bass reproduction speaker device - Google Patents

Abstract

(57) [Abstract] [Problem] A simple configuration, low cost, practical,
To provide a low-frequency sound reproduction speaker device having excellent low-frequency reproduction capability by equivalently increasing the volume in a cabinet. SOLUTION: In a low-frequency sound reproduction speaker device provided with a speaker unit 1, a cabinet 2 accommodating the speaker unit 1, and a means 4 for giving a negative stiffness to the vibration system,
The displacement of the vibration system is detected by the Hall element 5 and the movable magnet 3, and the detection signal is fed back to the power amplifier 6 for reproducing the source signal that drives the speaker unit 1 by the feedback circuit 6. As a result, the center of the vibration system of the speaker unit 1 in the displacement direction can be maintained at the original center position without separately providing an intake / exhaust pump, a control power amplifier, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-frequency sound reproduction speaker device for obtaining high low-frequency reproduction capability in a small cabinet.

[0002]

2. Description of the Related Art Generally, regarding low-frequency reproduction of a speaker,
There is an inverse relationship between the cabinet internal volume V, the low-frequency reproduction limit frequency fc, and the efficiency μ, and it is in principle very difficult to reproduce to a low frequency in a small cabinet without lowering the efficiency. Are known.

Further, if the stiffness of the air inside the cabinet can be reduced by utilizing the negative stiffness and the volume V inside the cabinet can be equivalently increased, the concept itself that the low frequency reproduction capability can be improved by escaping from this restriction can be achieved. Have been around for a long time. However, the reality is that there was no good way to implement this.

[0004] Here, conventional techniques that have been proposed in the past to embody this concept will be described. This prior art is disclosed in US Pat. No. 2810021 (LOW FREQUENCY LOUDSPEAKER, Pa.
tented Oct. 15, 1957), and U.S. Pat.
ROACOUSTIC TRANSDUCER UNITWITH REDUCED RESONANT FR
EQUENCY AND MECHANICAL SPRING WITH NEGATIVE SPRING
STIFFNESS, PREFERABLY USED IN SUCH A TRANSDUCER U
NIT, Patented Aug. 19, 1986). Both have the same basic concept, but the latter has a more advanced configuration than the former.

FIGS. 8 and 9 show the structure of this conventional bass reproducing speaker device. 8 and 9, reference numeral 51 denotes an electrodynamic speaker unit, which includes a field section 51 a and a frame 5.
1b, voice coil 51c, damper 51d, edge 51
e, a vibration plate 51f is provided. Reference numeral 52 denotes a closed cabinet to which a speaker unit 51 is attached.

Reference numeral 51i denotes a reinforcing ring for reinforcing the diaphragm 51f, which is attached to the outer periphery of the diaphragm 51f. Reference numeral 54 denotes a pair of springs in which upper and lower two bow-shaped leaf springs are opposed to each other.
And two fixed-side support members 52a fixed to the frame 51b. In this conventional example, about three sets of the springs 54 are provided symmetrically with respect to the center axis in the vibration direction of the diaphragm 51f.

The reason why the fixed-side support members 52a are arranged on both sides of the movable-side support member 51g is that if only one side is used, an axial rotational force is generated on the reinforcing ring 51i, that is, on the diaphragm 51f, so that the speaker unit 51 is supported. This is because stress is applied to the system, leading to breakage.

Reference numeral 58 denotes a means for detecting a deviation of the vibration plate 51f from the center of vibration. The specification of US Pat. No. 4,607,382 includes a capacitance detection method, an inductance detection method, a light amount detection method, and a cabinet. It refers to the internal air pressure detection method.

Reference numeral 59 denotes a control device for correcting a deviation of the diaphragm 51f from the center of the vibration, which is operated by an output signal from the detecting means 58. And in FIG. 8,
Reference numeral 60 denotes an intake / exhaust pump which operates according to an output signal of the control device 59. In FIG. 9, the control device 59 is a high-output power amplifier provided separately from a normal power amplifier for amplifying a source signal.
It is connected to the.

The operation of the conventional low-frequency sound reproduction speaker device configured as described above will be described with reference to FIGS. 10 and 11 show the action of the negative stiffness by the spring 54. FIG. In FIG. 10, 52a is a fixed-side support member, 51g is a movable-side support member, and 54 is a pair of springs compressed and attached by both. That is, one unit of the spring 54 shown in FIGS. 8 and 9 is shown.

When the position of the movable-side support member 51g is exactly at the center of the vibration displacement direction x, that is, at x = 0, the direction of the repulsive force of the spring 54 acting between the movable-side support member 51g and the fixed-side support member 52a is Since it is perpendicular to the x direction and the force vector component in the x direction becomes zero, no force in the x direction is generated.

However, when the position of the movable-side support member 51g is deviated from the center, that is, when the position of the movable-side support member 51g is, for example, the position of Δx in FIG. 10, the spring acting between the movable-side support member 51g and the fixed-side support member 52a. Since the direction of the repulsive force at 54 is not perpendicular to the x direction, a force vector component in the x direction is generated, and a force for pushing the movable-side support member 51g in the Δx direction is generated.

When the movable-side support member 51g is displaced by Δx, the force applied by the sealed air in the cabinet 52 to the vibration system of the speaker unit 51 is given by F1 in addition to the support system of the speaker unit 51 such as the edge 51e. Then, needless to say, the polarity of the stiffness of the force of F1 is
The value is positive because the movable side support member 51g is to be pulled back to the center of x = 0.

On the other hand, assuming that the force generated when the spring 54 is displaced by Δx is F2, the direction of F2 is opposite to that of F1 because F2 tends to push the movable-side support member 51g in the direction of displacement. The polarity of the stiffness is negative.

Therefore, a negative stiffness force is generated by the spring 54. The effect of this negative stiffness is shown in FIG.
Shown in In FIG. 11, the broken line indicates the relationship between the positive stiffness of the speaker unit support system and the air inside the cabinet applied to the vibration system, that is, the movable side support member 51g, and the displacement in the x direction. Similarly, the dashed line indicates the negative stiffness of the spring 54. The solid line indicates the relationship between the force applied to the movable-side support member 51g and the displacement in the x direction, and the solid line indicates the relationship between the force applied to the movable-side support member 51g and the stiffness obtained by adding them together in the x-direction.

The positive stiffness is F1 / △ x, which corresponds to the slope of the broken line. The negative stiffness is F2 / △ x, which corresponds to the dashed line gradient. The total stiffness is Ft / △ x, that is, (F1−F2) / △ x, which corresponds to the gradient of the solid line. This slope is smaller than the dashed slope, which will reduce the total stiffness.
In this manner, the stiffness finally applied to the movable-side support member 51g is reduced by the action of the negative stiffness, so that an effect equivalent to a reduction in the stiffness of the air inside the cabinet is obtained. Accordingly, since the stiffness of the air inside the cabinet is inversely proportional to the volume inside the cabinet, the effect of increasing the inside volume of the cabinet 52 equivalently is obtained.

In order to obtain this effect sufficiently, the negative stiffness of the spring 54 must be increased. However, in this case, the support system of the speaker unit 51 loses the negative stiffness force, and the vibration system of the speaker unit 51 is biased to a position deviated from the displacement center position x = 0, so that normal operation cannot be performed. .

Although the sum of the stiffness of the air inside the cabinet 52 and the stiffness of the support system of the speaker unit 51 is larger than the negative stiffness, a small amount of air leaks from the cabinet 52 and the diaphragm 51f. Therefore, if the negative stiffness exceeds the stiffness of the support system of the speaker unit 51, the vibration system cannot stop at the displacement center position.

The detecting means 58 and the control device 5 shown in FIGS.
9. The intake / exhaust pump 60 is provided to prevent and correct this. For example, in the configuration of FIG. 8, when the average vibration displacement center of the vibration system of the speaker unit 51 is deviated forward from the original center position (the position of x = 0 in FIG. 10), the displacement is biased. Is detected by the detecting means 58 to generate a signal and send an output signal to the control device 59. Then, the control device 59 causes the intake / exhaust pump 60 to perform an exhaust operation to exhaust the air in the cabinet 52, and returns the diaphragm 51f of the speaker unit 51 to the original displacement center position.

Conversely, when the vibration system is deviated rearward, the intake / exhaust pump 60 performs a suction operation to draw air into the cabinet 52 and pushes the vibration system of the speaker unit 51 back to the original displacement center position. .

Referring to the configuration of FIG. 9, when the vibration system of the speaker unit 51 is biased forward, the control unit 5
9, that is, the power amplifier causes a current to flow through the voice coil 51c of the speaker unit 51 to return the vibration system to the original displacement center position. Conversely, when the vibration system is biased backward, the control device 59 controls the voice coil 51 c of the speaker unit 51.
, And the vibration system is pushed back to the original displacement center position.

The voice coil 51c needs to have a double voice coil structure, that is, a voice coil for flowing the current of the control device 59 and an original voice coil for reproducing the source signal.

Therefore, with the low-frequency sound reproduction speaker device having the conventional configuration as described above, the inner volume of the cabinet is equivalently increased by negative stiffness while compensating for the bias of the displacement direction of the vibration system of the speaker unit 51. The range reproduction ability can be improved. A more detailed description of the principle of equivalently increasing the internal volume of the cabinet by negative stiffness and improving the low-frequency reproduction capability will be given in the embodiments of the present invention.

[0024]

However, in the above-mentioned conventional configuration, in order to correct the bias in the displacement direction of the vibration system of the speaker unit 51, a power amplifier different from the intake / exhaust pump and the power amplifier for reproducing the source signal is used. However, there is a problem that the apparatus is complicated, large-scale, and costly. There is also a problem that reliability is poor because mechanical fatigue is apt to occur in the spring 54.

That is, although there was a concept of improving the low-frequency reproduction capability by equivalently increasing the internal volume of the cabinet, it was not practical with the low-frequency reproduction speaker device according to the prior art.

The present invention solves the above-mentioned conventional problems, and has a simple structure, low cost, high reliability, practical use, and an equivalently large cabinet internal volume. It is an object of the present invention to provide a bass reproduction speaker device having the same.

[0027]

In order to achieve this object, a low-frequency sound reproduction speaker device according to the present invention accommodates a speaker unit, means for providing a negative stiffness to a vibration system of the speaker unit, and the speaker unit. In a bass reproduction speaker device including a cabinet, a detection unit that generates an electric signal corresponding to a displacement of a vibration system of the speaker unit; The power amplifier is provided with a feedback circuit for feeding back an electric signal, and the power amplifier supplies power to the speaker unit for correcting bias in a displacement direction of a vibration system of the speaker unit in addition to source signal power.

Further, a movable magnet that moves together with the vibration system of the speaker unit and a Hall element that detects the magnetism of the movable magnet are used as the detection means.

Further, means for imparting negative stiffness to the vibration system of the speaker unit is compressed at a plurality of substantially central axis symmetrical portions between the center of the vibration system of the speaker unit and the vicinity of the outer periphery of the speaker unit. This is a plate-shaped spring attached and attached. Alternatively, the means for giving negative stiffness to the vibration system of the speaker unit is a movable magnet that moves together with the vibration system of the speaker unit, and a fixed magnet that applies a force in the vibration displacement direction of the speaker unit to the movable magnet. Things.

According to the present invention, it is possible to realize a low-frequency sound reproduction speaker device having a simple configuration, low cost, high reliability and practical, and excellent low-frequency reproduction capability.

[0031]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a bass unit including a speaker unit, a unit for providing a negative stiffness to a vibration system of the speaker unit, and a cabinet accommodating the speaker unit. In the reproduction speaker device, a detection unit that generates an electric signal according to a displacement of a vibration system of the speaker unit, and a feedback that feeds back the electric signal from the detection unit to a power amplifier for reproducing a source signal that drives the speaker unit. A power amplifier configured to supply to the speaker unit electric power for correcting a bias in the displacement direction of the vibration system of the speaker unit in addition to the source signal power. Thus, a low-frequency sound reproduction speaker device having a practical and excellent low-frequency reproduction capability can be realized.

According to a second aspect of the present invention, there is provided a movable magnet which moves together with a vibration system of the speaker unit,
The low-frequency sound reproduction device according to claim 1, wherein the hall element for detecting the magnetism of the movable magnet is the detection means, and a low-frequency sound reproduction speaker device with a simple configuration of the detection means can be realized.

According to a third aspect of the present invention, the means for providing a negative stiffness to the vibration system of the speaker unit is provided between the center of the vibration system of the speaker unit and the vicinity of the outer periphery of the speaker unit. The low-frequency sound reproduction speaker device according to claim 1 or 2 is a plate-like spring compressed and attached to a plurality of positions substantially symmetric with respect to the central axis, and a highly reliable low-frequency sound reproduction speaker device can be realized.

According to a fourth aspect of the present invention, a means for providing a negative stiffness to the vibration system of the speaker unit comprises: a movable magnet that moves together with the vibration system of the speaker unit; The low-frequency sound reproduction speaker device according to claim 1 or 2, wherein the low-frequency sound reproduction speaker device is a fixed magnet that applies a force in the vibration displacement direction of the unit.

According to a fifth aspect of the present invention, there is provided the bass according to any one of the first to fourth aspects, further comprising means for holding a vibration system of the speaker unit near a center position in a displacement direction when not operating. This is a reproduction speaker device, and a long-life low-frequency sound reproduction speaker device with little change over time can be realized.

According to a sixth aspect of the present invention, a self-holding solenoid is used as means for holding the vibration system of the speaker unit near the center position in the displacement direction when the speaker unit is not operated. This is a reproduction speaker device, and a low-frequency sound reproduction speaker device that can quickly enter an operating state can be realized.

According to a seventh aspect of the present invention, the operating current of the self-holding solenoid is supplied via a capacitor, and the return current of the self-holding solenoid is supplied by discharging the capacitor. 6. The low-frequency sound reproduction speaker device according to item 6, wherein a low-frequency sound reproduction speaker device with high safety can be realized.

[0038] The invention according to claim 8 of the present invention is characterized in that a means for reducing the negative stiffness of the means for giving a negative stiffness to the vibration system of the speaker unit when not operating is provided. And a long-life low-frequency sound reproduction speaker device with little change over time can be realized.

According to a ninth aspect of the present invention, the loudspeaker unit further comprises means for varying the stiffness of the means for providing a negative stiffness to the vibration system of the speaker unit.
The low-frequency sound reproduction speaker device according to any one of the first to third aspects, and a low-frequency sound reproduction speaker device capable of changing low-frequency characteristics can be realized.

Hereinafter, the bass reproduction speaker device of the present invention will be described.
A description will be given based on a specific embodiment.

(Embodiment 1) FIG. 1 shows a structure of a bass reproduction speaker device of Embodiment 1. In FIG. 1, a field portion 1a, a frame 1b, a voice coil 1c, a damper 1
A speaker unit 1 including a d-side, an edge 1e, a diaphragm 1f, and a movable-side support member 1g also serving as a dust cap is attached to the closed cabinet 2. The movable magnet 3 is attached to the bobbin of the voice coil 1c, and moves together with the vibration system of the speaker unit 1 such as the voice coil 1c and the diaphragm 1f.

A movable support member 1g is attached to the tip of the long and extended bobbin of the voice coil 1c. On the outer peripheral side of the frame 1b of the cabinet 2,
The fixed-side support members 2a are fixed at four positions symmetric with respect to the central axis. Fixed side support member 2a and each movable side support member 1g
Between them, a pair of springs 4 with bow-shaped leaf springs facing each other are attached so as to be compressed from both ends. That is, the spring 4 applies a repulsive force to the movable-side support member 1g and the fixed-side support member 2a.
g, that is, a negative stiffness is given to the vibration system of the speaker unit 1.

Since all four springs 4 are the same and are mounted at symmetrical positions, the repulsive force is balanced in the horizontal direction, and the movable side support member 1g is maintained at the center in the horizontal direction. I'm dripping.

In the vicinity of the movable magnet 3, a Hall element 5 is arranged as detecting means for generating an electric signal according to the displacement of the vibration system. The speaker unit 1 is driven by a power amplifier 6 for reproducing a source signal. Hall element 5
Is output to the power amplifier 6 by the feedback circuit 5a, and the power for correcting the bias in the displacement direction of the vibration system of the speaker unit 1 is supplied from the power amplifier 6 to the voice coil 1c in addition to the source signal power. .

Hereinafter, the material, dimensions, performance, circuit configuration, and the like of the components of the bass reproduction speaker device will be specifically described.

The diameter of the speaker unit 1 is 18 cm. The field portion 1a uses a ferrite magnet having a diameter of 70 mm. The frame 1b has a diameter of 18 cm and is made of an iron plate. The diameter (nominal diameter) of the voice coil 1c is 25 mm
It is. The material of the edge 1e is urethane foam and has a down-roll shape. The diaphragm 1f is a cone made of paper. The material of the movable side support member 1g is resin.

The cabinet 2 is a closed type and has an internal volume of 1
It is as small as 0 liter. The material of the fixed-side support member 2a is a resin. The length of the bow-shaped leaf spring 4 is 10 cm when attached. The width of the spring 4 is 1 cm, and the material is a phosphor bronze plate.

Here, the principle of equivalently increasing the internal volume of the cabinet by negative stiffness and improving the low frequency reproduction capability will be described in more detail. The effective vibration mass of the speaker unit is M, and the lowest resonance frequency in the free air state is
Assuming f0, the stiffness Ks of the support system (damper or edge) of the speaker unit is expressed by the following equation: Ks = M × (2πf0) 2. Further, assuming that the effective vibration radius of the speaker unit is a, the air sound velocity is c, the air density is ρ, and the volume of the cabinet is V, the stiffness Kc given by the air in the cabinet to the speaker unit vibration system is Kc = ρc2 (πa) 2 / V
... Equation When the speaker unit is mounted on the cabinet, the stiffness of Ks + Kc works on the speaker unit vibration system. The lowest resonance frequency at this time is f1
Then, f1 = (Ks + Kc) 1/2 / 2πM1 / 2...

Here, the magnitude of the negative stiffness is assumed to be Kn. Then, the stiffness acting on the vibration system of the speaker unit becomes Ks + Kc−Kn, which corresponds to the stiffness of the air in the cabinet changing from Kc to Kc−Kn. Since the stiffness of the air in the cabinet is inversely proportional to the internal volume according to the equation, this is equivalent to increasing the internal volume of the cabinet from 1 / Kc to 1 / (Kc−Kn).

When the negative stiffness acts, the minimum resonance frequency of the speaker unit attached to the cabinet is f1 = (Ks + Kc-Kn) 1/2 / 2πM1 / 2..., The minimum resonance frequency becomes ｛(Ks + Kc −Kn) / (Ks
+ Kc)｝ 1/2, that is, the low-frequency reproduction limit frequency is extended correspondingly, and the low-frequency reproduction capability is improved.

When the technique of the negative stiffness is not used, in order to lower the lowest resonance frequency, the effective vibration mass must be increased or the effective vibration area must be reduced, so that the efficiency is lowered. On the other hand, if negative stiffness is used, the lowest resonance frequency can be reduced without doing so, so that the low range can be extended without lowering the efficiency.

Based on the principle described above, a description will be given of the calculation of the effect of equivalently increasing the internal volume of the cabinet and improving the low-frequency reproduction capability of the present embodiment. In the present embodiment, the minimum resonance frequency of the speaker unit 1 when the compression of the spring 4 is relaxed and no negative stiffness is generated is 6
0 Hz, the effective vibration mass is 15 g. The effective vibration radius is 70 mm. That is, the stiffness Ks of the support system of the speaker unit is Ks = 2130 (N / m) from the equation. Stiffness Kc given by air in cabinet 2
From the formula, Kc = 3290 (N / m). That is, Ks + K
c = 5420 (N / m). And the lowest resonance frequency of the speaker unit 1 attached to the cabinet 2
f1 is calculated from the formula as f1 = 96 Hz, and the actual measurement value is also the same.

The negative stiffness Kn obtained when the spring 4 was compressed and attached was 2800 (N / m).
Stiffness of support system of speaker unit 1 Ks = 213
0 (N / m). And the total stiffness is Ks + Kc-Kn = 5420-2800 = 2620 (N / m)
According to the first embodiment, the lowest resonance frequency, that is, the low-frequency reproduction limit frequency can be significantly extended from 96 Hz to 67 Hz.

This means that the volume inside the cabinet is 1/3290
From 1 / (3290-2800) = 1/490. That is, the effect of increasing the inner volume of the cabinet 2 several times equivalently is obtained.

Next, a configuration for correcting a bias in the displacement direction of the vibration system of the speaker unit 1 will be described in detail.

The dimensions of the movable magnet 3 are 5 mm in length and width, 3 mm in thickness, and the material is ferrite. The movable magnet 3 is magnetized in the vertical direction, that is, in the vertical height direction in FIG. 1, and the upper side is the N pole and the lower side is the S pole. The Hall element 5 is arranged in the vertical and vertical directions near the center of the movable magnet 3 in the vertical direction. The distance between them is about 3 mm.

The Hall element 5 generates an output signal according to a magnetic flux vector generated by the movable magnet 3 in the horizontal direction. At the center position of the movable magnet 3 in the vertical direction, the magnetic flux passes in the vertical direction immediately below the N pole to the S pole, so that the horizontal magnetic flux vector becomes zero. Therefore, when the vertical center position of the movable magnet 3 matches the vertical center position of the Hall element 5, no signal is output because the magnetic flux passing horizontally through the Hall element 5 is zero.

When the movable magnet 3 is displaced up or down, the magnetic flux distribution becomes asymmetric at the position of the Hall element 5.
Since one of the poles approaches, a magnetic flux vector in the horizontal direction is generated. At this time, an electric signal is generated from the Hall element 5. Needless to say, if, for example, the Hall element 3 generates a positive electric signal when the N pole approaches,
When the pole side approaches, the direction of the horizontal magnetic flux vector is reversed, so that a negative electric signal is generated. That is, with this configuration, an electric signal corresponding to the displacement of the vibration system of the speaker unit 1 can be obtained.

When the average vibration displacement center of the vibration system of the speaker unit 1 is at the original center position, that is, when there is no deviation in the displacement direction, the Hall element is activated when low-frequency AC power is applied to the speaker unit 1. 5 is symmetrical on the plus side and the minus side with respect to the zero level, and the electric signal becomes zero by integrating this. However, when the displacement of the vibration system is deviated in the displacement direction, the level on either the positive side or the negative side becomes large (that is, a bias is generated), so that an electric signal is generated even after integration.

In the present embodiment, for example, when the vibration system of the speaker unit 1 starts to be biased to one side, a current in a direction of returning the same to the opposite direction, that is, returning to the original displacement center position, is transmitted from the power amplifier 6 to the speaker unit 1. The Hall element 5 and the feedback circuit 5a are configured to be supplied.

FIG. 2 shows an example of a circuit diagram of the feedback circuit 5a including the detection means 5, the feedback circuit 5a, and the power amplifier 6 according to the present embodiment. In FIG. 2, terminals 1 and 3 of the Hall element 5 are drive current supply terminals. Reference numerals 2 and 4 denote output terminals, at which a detection voltage is generated. OP1 is an operational amplifier in a buffer amplification unit, and OP2 is an operational amplifier in an integration circuit unit. P-AMP is a general audio IC power amplifier, and its output is 30W.

C3 is an integrating capacitor, and the amplification gain of OP2 attenuates as the frequency increases. As a result, feedback is applied only to the very low frequency component signal corresponding to the biased movement of the vibration system of the speaker unit 1. In other words, no feedback is applied to the movement of the vibration system of the audio source such as music at a low frequency of several tens of Hz or more, so that there is no adverse effect on the low frequency. VR is a volume for adjusting offset, and can adjust the output voltage of the feedback circuit to zero when the vibration system of the speaker unit 1 is at the original center position.

The feedback circuit 5a supplies a current corresponding to the very low frequency component signal fed back to the + terminal of the P-AMP to the speaker 1 so that the power for correcting the bias in the displacement direction of the vibration system can be supplied to the speaker 1. The P-AMP portion connected to the circuit 5a has a DC amplifier configuration.

However, terminals IN and P-
A DC cut capacitor C1 is inserted between the power amplifier 6 and the AMP, and the entire power amplifier 6 operates in the same manner as a normal audio power amplifier. In other words, only one power amplifier 6 can supply the speaker unit 1 with both the power of the audio source signal and the power for correcting the bias in the displacement direction of the vibration system.

With such a configuration, the speaker unit 1
The servo that always corrects the slight deviation in the displacement direction of the vibration system and keeps it at the original center position in the displacement direction is applied. Even if the negative stiffness is large, the average displacement center position of the vibration system is the original center position. , An extremely stable operation was obtained.

In other words, in the present embodiment, it is not necessary to separately provide a conventional intake / exhaust pump and a control power amplifier in order to correct the bias in the displacement direction of the vibration system. Further, needless to say, the voice coil 1c of the speaker unit 1 does not need to be a double voice coil. In addition, the configurations of the detecting means 5 and the feedback circuit 5a are simple, and all the parts used are inexpensive.

In the conventional configuration described with reference to FIG. 8, when the speaker unit 51 has the same diameter of 18 cm, the length of the spring 54 attached between the movable-side support member 51g and the fixed-side support member 52a is small. Although only about 5 cm can be taken, in the first embodiment, the spring 4 is attached between the center of the vibration system of the speaker unit 1 and the outer periphery of the frame 1b, that is, the movable-side support member 1g
Since the length of the spring 4 attached between the spring 4 and the fixed-side support member 2a can be increased to 10 cm,
Very low mechanical fatigue.

Therefore, according to the present embodiment, as described above, a low-frequency sound reproduction speaker device having a simple configuration, low cost, high reliability, and practical and excellent low-frequency reproduction capability can be realized. .

In this embodiment, the movable magnet 3
Is attached to the voice coil 1c, but may be attached to other parts of the vibration system of the speaker unit 1. An elastic body or the like may be interposed between the movable magnet 3 and the vibration system of the speaker unit 1, and the movable magnet 3 and the vibration system may move together in a low frequency range. However, it is better not to bring the Hall element 5 too close to the field portion 1a. Field part 1a
This is because the magnetic flux leaking from the surface has an effect.

In this embodiment, the speaker unit 1
Is a normal electrodynamic type, but it can be applied to other electroacoustic conversion type speaker units such as a motor drive type and an electromagnetic type.

In this embodiment, the means for providing negative stiffness is a mechanical means using a spring.
Needless to say, magnetic means may be used as described in the second embodiment. In addition, electrostatic means using a repulsive force between charges of the same polarity may be used.

In the present embodiment, four springs 4 are arranged symmetrically with respect to the central axis, but may be three or other numbers. When the negative stiffness generated by the spring 4 is not so large, it is possible to use two springs.

Further, in the present embodiment, the spring 4 is a bow-shaped leaf spring made of phosphor bronze, but other materials and shapes are also possible. For example, if the material is a shape memory alloy, metal fatigue is reduced and reliability is improved.

In the present embodiment, the fixed-side support member 2a
Is fixed to the cabinet 2, but the length of the spring 4 can be sufficiently secured even when the speaker unit 1 is attached to the outer peripheral portion of the frame 1b of the speaker unit 1.

In the present embodiment, the cabinet 2 is a closed type. However, if the rear of the speaker unit is closed, a cabinet type other than the closed type, for example, a Kelton type can be applied.

In this embodiment, the Hall element 5 is used as the detecting means. However, it goes without saying that other types of detecting means, for example, the following types of detecting means are also possible.
That is, an optical system that detects a change in the amount of light with a CDS, a photodiode, a phototransistor, or the like, an electrostatic system that detects a capacitance between a movable electrode and a fixed electrode attached to a vibration system of a speaker unit, a speaker unit And an induction method for detecting a change in inductance of the coil by using an iron plate attached to the vibration system and a coil arranged near the iron plate.

However, when a Hall element is used as the detecting means, the simplest configuration can be obtained. The reason is that the speaker unit 1 is used in the optical system, the electrostatic system, and the induction system.
In order to determine whether the displacement of the vibration system is above or below the center position, it is necessary to dispose two detection elements at the top and bottom. In the first embodiment, the movable magnet 3 has two N poles and S poles. The Hall element 5 generates a positive or negative electric signal depending on the displacement of the vibration system of the speaker unit 1 because of the two polarities. That is, it is possible to determine whether the displacement of the vibration system of the speaker unit 1 is up or down with one detection element.

In the present embodiment, the Hall element 5 is used as the detecting means. However, if a Hall IC is used instead, the feedback circuit can be simplified.

In Embodiment 1, the signal feedback from the feedback circuit 5a to the power amplifier 6 is performed purely electrically.
It may be performed via a photocoupler.

In the present embodiment, the portion of the power amplifier 6 that receives the feedback signal has a DC amplifier configuration. However, if a problem arises when DC amplification is performed, a non-DC amplifier configuration may be used. is there. For example, a large-capacity capacitor may be inserted between the resistor R1 and the ground in the circuit diagram of FIG. 2 so that amplification at an extremely low frequency is not performed but amplification at an extremely low frequency may be performed.

In addition, it goes without saying that the present invention is not limited to the above-described example.

(Embodiment 2) The configuration of a bass reproduction speaker device according to Embodiment 2 of the present invention will be described with reference to FIG. 3, but a field portion 11a, a frame 11b, and a damper 11 will be described.
d, edge 11e, diaphragm 11f, cabinet 12,
Since the detecting means 15 and the power amplifier 16 are exactly the same as those in the first embodiment described with reference to FIG. 1, a specific description thereof will be omitted here.

In the present embodiment, the voice coil 11c has a diameter of 25 mm as in the first embodiment, but the bobbin is not extended as in the first embodiment and has a normal length. Then, a dust cap 11g is attached to the diaphragm 11f.

The major difference in the present embodiment is that
A means for providing negative stiffness to the vibration system of the speaker unit 11 includes a movable magnet 13 that moves together with the vibration system of the speaker unit 11 and a fixed magnet 14 that applies a repulsive force to the movable magnet 13 in the vibration displacement direction of the speaker unit 11. It is that.

The movable magnet 13 has a ring shape, and is attached to the voice coil 11c to be mounted on the speaker unit 1.
It moves with one vibration system. A fixed magnet 14 is mounted on the inner peripheral side of the same vertical center position as the movable magnet 13 by a support member 11h made of resin.
The movable magnet 13 has an outer diameter of 30 mm and an inner diameter of about 2 mm.
5mm, 3mm thick, material is 32 magnetic energy products
It is neodymium of MG Oe (Mega Gauss Oersted). The fixed magnet 14 has a cylindrical shape with a size of 22 mm in diameter and a thickness of 10 mm, and is made of a movable magnet 13.
Is the same as

The movable magnet 13 and the fixed magnet 14 are both magnetized with the N pole on the upper side and the S pole on the lower side, and repel each other. When the vertical center positions of the movable magnet 13 and the fixed magnet 14 exactly coincide with each other, no force is generated in the vertical direction, that is, in the displacement direction of the vibration system of the speaker unit 11.

However, when the movable magnet 13 is displaced, a vertical vector is generated in the direction of the repulsive force, so that the movable magnet 13 generates a force that is further pushed out in the direction of displacement, that is, a negative stiffness. The negative stiffness obtained in the case of the second embodiment is also substantially the same as that obtained in the first embodiment.

Similarly to the first embodiment, when the fixed magnet 14 is removed and there is no negative stiffness, the minimum resonance frequency of the speaker unit 11 is 60 Hz, the effective vibration mass is about 15 g, and the effective vibration radius is 70 mm.

As in the first embodiment, the Hall element 15 serving as the detecting means is arranged in the vertical and vertical directions near the center of the movable magnet 13 in the vertical direction. That is, the movable magnet 13 which is a negative stiffness generating means is shared for detection.

In the present embodiment, since the movable magnet 13 is stronger than in the first embodiment, the detected voltage level of the Hall element 15 is higher than that in the first embodiment. Then feedback circuit 1
The gain of 5a is smaller than that of the first embodiment described with reference to FIG. 2, and specifically, the value of the resistor R8 in FIG. 2 is smaller than that of the first embodiment. This is because if the feedback loop gain is too high, there is a risk that oscillation will occur.

The bass reproducing apparatus according to the second embodiment configured as described above has the same effects as those described in the first embodiment. In other words, the lowest resonance frequency, that is, the low-frequency reproduction limit frequency can be significantly extended from 96 Hz to slightly lower than 70 Hz by negative stiffness while correcting the bias in the displacement direction of the vibration system of the speaker unit 11.

Further, in this embodiment, since the generation of negative stiffness is not a mechanical means, there is no generation of mechanical fatigue, and the reliability is very high.

Therefore, as described above, according to the present embodiment, a low-frequency sound reproduction speaker device having a simple structure, low cost, particularly high reliability, practical, and excellent low-frequency reproduction capability is provided. Can be realized.

In the present embodiment, the movable magnet 1
3 and the fixed magnet 14 are configured as described above,
Other various configurations are possible. For example, the fixed magnet 14 may be arranged in a ring shape on the outer periphery of the movable magnet 13 (in this case, the Hall element 15 may be arranged on the inner periphery of the movable magnet 13), or the fixed magnet 4 or the movable magnet 3 may be provided with an iron plate. Or a yoke may be attached.

In this embodiment, the movable magnet 1
Although the magnetization directions of the magnet 3 and the fixed magnet 14 are set to the vertical direction, that is, the thickness direction of the magnet, they may be magnetized in the radial direction so that they repel each other.

In this embodiment, the Hall element 15 detects the magnetic flux of the movable magnet 13 that generates negative stiffness. However, a small magnet is attached to the vibration system separately from the movable magnet, and the magnetic flux is removed. It may be detected.

In addition, it goes without saying that the present invention is not limited to the above-described example.

(Embodiment 3) The structure of a bass reproduction speaker device according to Embodiment 3 of the present invention will be described with reference to FIG. 4, but a field portion 21a, a frame 21b, a voice coil 21c, a damper 21d, an edge 21e, Diaphragm 21f,
Cabinet 22, fixed-side support member 22a, movable magnet 23, spring 24, detection means 25, feedback circuit 2
5a and the power amplifier 26 are completely the same as those in the first embodiment described with reference to FIG. 1, and therefore, detailed description thereof is omitted here.

The present embodiment is different from the first embodiment in that means 27a and 27 for holding the vibration system of the speaker unit 21 near the center position in the displacement direction when the bass reproducing speaker device is not operating.
b, 21 g.

Reference numeral 27a denotes a small gear motor, and a rotary shaft 27b projects from the center. Shaft 27
The leading end of b is bent in a U-shape so that the movable-side support member 21g can be sandwiched between the upper and lower sides with a slight clearance. 21g is a movable support member to which a spring 24 also serving as a dust cap is attached.
A small relief hole having a size slightly larger than the front circumference of the bent portion of the end of the rotating shaft 27b is provided at the center.

During the operation of the bass reproduction speaker device, the direction of the bent end of the rotary shaft 27b coincides with the clearance hole of the movable-side support member 21g. In this way, during the operation of the bass reproduction speaker device, the vibration system of the speaker unit 21 can move without the movable-side support member 21g coming into contact with the bent end of the rotary shaft 27b.

When the low-pitched sound reproduction speaker device is not operated, for example, when the power of the low-pitched sound reproduction speaker apparatus is turned off, the gear motor 27a rotates the rotary shaft 27b by several tens of degrees. Then, as shown in FIG.
The direction of the bent end of the movable member 21 is displaced from the escape hole of the movable-side support member 21g, and the movable-side support member 21g is sandwiched from both upper and lower sides with a small clearance to hold the vibration system of the speaker unit 21 near the center position in the displacement direction.

The operation control of the gear motor 27a may be performed as follows. When the power of the low-frequency sound reproduction speaker device is turned on, the rotating shaft 27b is rotated after the vibration system of the speaker unit 21 moves from the biased position to the center position in the displacement direction to release the holding of the vibration system. For several seconds until the rotating shaft 27b moves to a predetermined position and stops, the source input signal of the power amplifier is muted. This series of operations can be easily realized by a simple delay circuit or the like.

In order to cope with the case where the power of the low-frequency sound reproduction speaker device is turned off, a relay that operates about 1-2 seconds later than the main body power switch touched by the user may be provided inside the device. That is, at the moment when the user turns off the main body power, only the source input to the power amplifier 26 is cut off, and immediately after that, the geared motor 27a is operated to hold the vibration system of the speaker unit 21 near the center position in the displacement direction. Then, after the geared motor 27a stops, the entire power supply such as the power amplifier 26 and the feedback circuit 25 may be shut off by the relay.

The bass reproducing apparatus according to the present embodiment having such a configuration not only provides the same effects as those described in the first embodiment, but also operates the speaker unit 21 when the bass reproducing speaker apparatus is not operating. Since the vibration system is held in the vicinity of the center position in the displacement direction, a long time does not elapse on one side. For this reason, the stress due to the support system of the speaker unit 21, that is, the tension of the damper 21d and the edge 21e can be eliminated, so that the change with time and deterioration of the support system are reduced.

Also, since the spring 24 is held at the equilibrium position, there is no fear that the negative stiffness of the spring 24 becomes vertically asymmetric, which tends to occur when the spring 24 remains deformed for a long time.

Therefore, as described above, according to the present embodiment, a long-life low-frequency sound reproduction speaker device with little change over time can be realized.

In the present embodiment, the movable support member 2
A slight air leak occurs from the 1 g escape hole. It is more desirable to provide a closed cover on the movable-side support member 21g because this is eliminated.

Further, in the present embodiment, the movable support member 2
Although the vibration system of the speaker unit 21 is held near the center position in the displacement direction by using the tip portion of 1 g, it goes without saying that other members or parts may be used.

In this embodiment, the geared motor 2
Although 7a is used as a means for holding the vibration system of the speaker unit 21 in the vicinity of the center position in the displacement direction, this may be used as a rotary solenoid or other means.

In addition, it goes without saying that the present invention is not limited to the above-described example.

(Embodiment 4) The configuration of a bass reproduction speaker device according to Embodiment 4 of the present invention will be described with reference to FIG. 5, but a field portion 31a, a frame 31b, a voice coil 31c, a damper 31d, an edge 31e, Diaphragm 31f,
The movable-side support member 31g, the cabinet 32, the fixed-side support member 32a, the movable magnet 33, the spring 34, the detection means 35, the feedback circuit 35a, and the power amplifier 36 are completely the same as those in the first embodiment described with reference to FIG. Here, a detailed description of these will be omitted.

In the present embodiment, as in the third embodiment, when the low-frequency sound reproduction speaker device is not operating, the speaker unit 31
Is provided near the center position in the displacement direction, but differs in that a self-holding solenoid 37a is used. A plunger 37b that moves in the direction of the central axis projects from the center of the self-holding solenoid 37a, and the tip of the plunger 37b fits into a resin holding fitting member 37c attached to the bobbin of the voice coil 31c. Have been. The return spring 3 is attached to the plunger 37b.
7d is attached.

During operation of the bass reproduction speaker device, the plunger 37b is instantaneously sucked as soon as the self-holding solenoid 37a is energized, and the plunger 37b immediately comes off the holding fitting member 37c. When the bass reproduction speaker device operates, the vibration system of the speaker unit 31
The holding fitting member 37c can move without contacting the tip of the plunger 37b.

Since the solenoid 37a is a self-holding solenoid, the plunger 37b is kept in the suction state, so that the power can be released immediately after the suction. That is, energization is only required for a moment.

When the low-frequency sound reproduction speaker device is not operated, for example, when the power of the low-frequency sound reproduction speaker device is turned off, the self-holding solenoid 37a is energized in the reverse direction. A so-called return current flows. Then, the plunger 37b is released from the suction state, and returns to the position of the holding fitting member 37c by the force of the return spring 37d. Thus, the vibration system of the speaker unit 31 is held near the center position in the displacement direction.

FIG. 6 shows an example of a circuit diagram for controlling the operation of the self-holding solenoid 37a. ACD is an AC primary side current detection circuit of the bass reproduction speaker device.
The coil of the self-holding solenoid 37a is energized by using a large-capacity capacitor C2. The operation of this control circuit is as follows.

When the power switch of the low-pitched sound reproduction speaker device is turned on, the AC primary current detection circuit ACD generates a detection electric signal, and a current starts flowing to the base of the transistor Q.
A capacitor C1 and a resistor R are connected to the transistor Q. With this time constant, the relay RR connected to the emitter of the transistor Q operates about one second after the power switch is turned on. The operation is performed after about one second in order to wait for the vibration system of the speaker unit 31 to move from the biased position to the center position in the displacement direction.

Then, the relay RR is turned on to connect the terminals 1 and 2, and a current instantaneously flows from the power supply side to the self-holding solenoid 37a through the capacitor C2, and the self-holding solenoid 37a operates to enter the suction state. Become. This current is a charging current for the capacitor C2, but only for a moment, so that it is not necessary to continuously supply unnecessary current to the self-holding solenoid 37a.

When the power switch of the low-pitched sound reproduction speaker device is turned off, the detection electric signal from the AC primary current detection circuit ACD disappears, so that the transistor Q is turned off and the relay RR is turned off. Then, the terminals 1 and 3 of the relay RR are connected, and the self-holding solenoid 37
The capacitor C1 discharges to a, but the direction of the current at this time is opposite to that when the power switch of the bass reproduction speaker device is turned on. In this way, the reverse current flows through the self-holding solenoid 37a, so that the plunger 37b can be returned. Terminals 4 and 6 of relay RR
Is for discharging the time constant capacitor C1.

The bass reproducing apparatus of this embodiment having the above-described configuration not only provides the same effects as those described in the third embodiment, but also operates the self-holding solenoid 37a instantaneously. As in the geared motor used in the third embodiment, the operation state can be quickly entered without taking much time.

If there is no means for holding the vibration system of the speaker unit in the vicinity of the center position in the displacement direction, it is difficult to quickly turn on the bass reproduction speaker device after turning on the power. This is because, when the low-frequency sound reproduction speaker device is not operating, the vibration system is pushed away from the center position in the displacement direction by the force of the spring, and it takes some time to return to the center position in the displacement direction. is there.

In this embodiment, the operating current of the self-holding solenoid 37a is supplied through the capacitor C2, and the same capacitor is discharged to supply the return current of the self-holding solenoid 37a. There is no need to have a separate power supply for the current. As a result, if the power is suddenly cut off during operation of the bass reproduction speaker device,
For example, even in the event of a power outage or accidental disconnection of the power outlet, the self-holding solenoid 37a can be returned using the charge stored in the capacitor C2.
The vicinity of the center position of the vibration system of the speaker unit 31 in the displacement direction can be held.

Therefore, as described above, according to the present embodiment, not only the aging is small but the life is long,
It is possible to realize a low-frequency sound reproduction speaker device that can quickly enter an operation state and has high security.

In the present embodiment, the plunger 37b of the self-holding solenoid 37a is in the return state when the low-frequency sound reproduction speaker device is not operating, but the reverse design is also possible.

Although the self-holding solenoid 37a is used in the present embodiment, it can be designed as a normal solenoid or another type of solenoid. However, when a self-holding solenoid is used, power can be saved only by momentarily passing an operating current.

In addition, it goes without saying that the present invention is not limited to the above-described example.

(Embodiment 5) The configuration of a low-frequency sound reproduction speaker device according to Embodiment 5 of the present invention will be described with reference to FIG. 7, but a field part 41a, a frame 41b, a voice coil 41c, a damper 41d, an edge 41e, Diaphragm 41f,
Movable side support member 41g, cabinet 42, movable magnet 43, spring 44, detecting means 45, feedback circuit 4
5a and the power amplifier 46 are exactly the same as those in the first embodiment described with reference to FIG. 1, and a detailed description thereof will be omitted here.

A feature of this embodiment is that a movable rod 42b is provided in a fixed-side support member 42a for fixedly supporting the spring, so that the negative stiffness of the spring 44 can be changed.

Specifically, the four fixed-side support members 42a and the movable rods 42b in FIG. 7 have built-in axially propulsion movable mechanisms such as a motor, a worm gear, and a rack gear. When the rotation of the motor stops, the worm gear and the rack gear do not move even if a compressive force is applied to the movable rod 42b, so that the movable rod 42b acts as a stationary fixed end.

When the low-frequency sound reproduction speaker device is not operating, the movable rod 42b is retracted to loosen the spring 44. During the operation of the bass reproduction speaker device, the movable rod 42b is advanced to apply a predetermined compressive force to the spring 44. Alternatively, by adjusting the rest position of the movable rod 42b, the compression force applied to the spring 44 can be adjusted, so that the generated negative stiffness can be varied.

The bass reproducing apparatus according to the present embodiment having the above-described structure not only provides the same effects as those described in the first embodiment, but also reduces the negative stiffness of the spring 44 when not operating. The support system of the speaker unit 41, that is, the damper 41d and the edge 41e
Are not stretched, and the support system is less likely to change over time and deteriorate.

Since the negative stiffness generated by the spring 44 can be adjusted, the lowest resonance frequency of the low-frequency sound reproduction speaker device can be adjusted, and the low-frequency characteristics can be varied.

Therefore, as described above, according to the present embodiment, not only is there a small change with time but a long life, but also
A low-frequency sound reproduction speaker device capable of changing low-frequency characteristics can be realized.

In the fifth embodiment, the means for providing negative stiffness is a mechanical means, that is, the spring 44. However, a magnetic means as described in the second embodiment may be used. In this case, for example, by using a fixed magnet as an electromagnet and adjusting the current supplied thereto, the generated negative stiffness can be varied.

In addition, it goes without saying that the present invention is not limited to the above-described example.

[0137]

As described above, according to the low-frequency sound reproduction speaker device of the present invention, there are provided a speaker unit, means for giving a negative stiffness to the vibration system of the speaker unit, and a cabinet for accommodating the speaker unit. In the bass reproduction speaker device, the detection means for generating an electric signal according to the displacement of the vibration system of the speaker unit, and the electric signal from the detection means are fed back to a power amplifier for reproducing the source signal for driving the speaker unit. The power amplifier supplies the speaker unit with power for correcting the bias in the displacement direction of the vibration system of the speaker unit in addition to the source signal power. A sensor that constantly corrects slight deviations in the displacement direction and maintains it at the original center position in the displacement direction. Not only to obtain an extremely stable operation in which the average displacement center position of the vibration system is maintained at the original center position even if the negative stiffness is large, and to correct the bias in the displacement direction of the vibration system. There is no need to separately provide a conventional intake / exhaust pump or a control power amplifier. Therefore, it is possible to realize a low-frequency sound reproduction speaker device having a simple configuration, low cost and practical, and excellent low-frequency reproduction capability.

According to the low frequency sound reproduction speaker device of the second aspect of the present invention, the movable magnet which moves together with the vibration system of the speaker unit and the Hall element for detecting the magnetism of the movable magnet are used as the detection means. , 1
It is possible to determine whether the displacement of the vibration system of the speaker unit is up or down using the individual elements. Therefore, it is possible to realize a low-frequency sound reproduction speaker device in which the configuration of the detection means is simplified.

According to the low-frequency sound reproduction speaker device of the third aspect of the present invention, the means for imparting negative stiffness to the vibration system of the speaker unit includes a center portion of the vibration system of the speaker unit and an outer peripheral portion of the speaker unit. By using a spring that is compressed and attached to a plurality of locations substantially symmetric with respect to the central axis, the length of the spring can be increased and mechanical fatigue can be reduced. Therefore, a highly reliable bass reproduction speaker device can be realized.

According to the low-frequency sound reproduction speaker device of the fourth aspect of the present invention, the means for imparting negative stiffness to the vibration system of the speaker unit is provided by the movable magnet moving with the vibration system of the speaker unit, and the movable magnet. On the other hand, by using a fixed magnet that applies a force in the vibration displacement direction of the speaker unit, there is no mechanical fatigue since negative stiffness is not generated by mechanical means. Therefore, a particularly reliable bass reproduction speaker device can be realized.

According to the low-frequency sound reproduction speaker device of the fifth aspect of the present invention, the means for holding the vibration system of the speaker unit in the vicinity of the center position in the displacement direction when not operating is provided. During non-operation, the vibration system of the speaker unit is not biased to one side in the displacement direction and does not elapse for a long time, and a long-time stress is not applied to the support system and the spring of the speaker unit. Therefore, a long-life low-frequency sound reproduction speaker device with little change over time can be realized.

According to the bass reproduction speaker device of the sixth aspect of the present invention, the self-holding solenoid is used as a means for holding the vibration system of the speaker unit near the center position in the displacement direction when not operating. The vibration system of the speaker unit can be instantaneously held or released near the center position in the displacement direction. Therefore, it is possible to realize a low-frequency sound reproduction speaker device which can be quickly put into an operating state.

According to the bass reproduction speaker device of the present invention, the operating current of the self-holding solenoid is supplied via the capacitor, and the return current of the self-holding solenoid is supplied by discharging the capacitor. With the supply, even when the power supply is suddenly cut off during the operation of the bass reproduction speaker device, the vicinity of the center position in the displacement direction of the vibration system of the speaker unit can be held. Therefore, a low-pitched sound reproduction speaker device with high security can be realized.

According to the low-frequency sound reproduction speaker apparatus of the eighth aspect of the present invention, the speaker unit is provided with means for reducing the negative stiffness of the means for giving a negative stiffness to the vibration system of the speaker unit when not operating. The support system of the unit no longer stretches. Therefore, a long-life low-frequency sound reproduction speaker device with little change over time can be realized.

According to the low frequency sound reproduction speaker device of the ninth aspect of the present invention, the negative stiffness generated by the means for changing the stiffness of the means for giving a negative stiffness to the vibration system of the speaker unit is provided. Since it can be adjusted, the lowest resonance frequency of the bass reproduction speaker device can be adjusted. Therefore, it is possible to realize a low-frequency sound reproduction speaker device capable of changing low-frequency characteristics.

As described above, the present invention has an extremely large practical value.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view and a front view illustrating a configuration of a low-frequency sound reproduction speaker device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a feedback circuit according to the first embodiment of the present invention;

FIG. 3 is a cross-sectional view and a front view showing a configuration of a bass reproduction speaker device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view and a front view showing a configuration of a low-frequency sound reproduction speaker device according to a third embodiment of the present invention.

FIGS. 5A and 5B are a cross-sectional view and a front view showing a configuration of a bass reproduction speaker device having another configuration according to Embodiment 3 of the present invention. FIGS.

FIG. 6 is a diagram illustrating an example of a control circuit that controls the operation of the solenoid according to the embodiment;

FIGS. 7A and 7B are a cross-sectional view and a front view showing a configuration of a low-frequency sound reproduction speaker device according to a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view and a front view showing the configuration of a conventional bass reproduction speaker device.

FIG. 9 is a sectional view and a front view showing the configuration of a conventional bass reproduction speaker device.

FIG. 10 is an explanatory view showing the operation of a spring that provides negative stiffness.

FIG. 11 is a graph showing displacement to force characteristics of stiffness.

[Explanation of symbols]

1, 11, 21, 31, 41 Speaker units 1a, 11a, 21a, 31a, 41a Field units 1b, 11b, 21b, 31b, 41b Frames 1c, 11c, 21c, 31c, 41c Voice coils 1d, 11d, 21d, 31d, 41d Damper 1e, 11e, 21e, 31e, 41e Edge 1f, 11f, 21f, 31f, 41f Diaphragm 1g, 21g, 31g, 41g Movable support member 11g Dust cap 11h Support member 2, 12, 22, 32, 42 Cabinet 2a, 22a, 32a, 42a Fixed side support member 42b Movable rod 3, 13, 23, 33, 43 Movable magnet 4, 24, 34, 44 Spring 14 Fixed magnet 5, 15, 25, 35, 45 Hall element 5a , 15a, 25a, 35a, 45a Feedback circuit , 16, 26, 36 and 46 a power amplifier 27a geared 37a self-hold solenoid 27b rotating shaft 37b plunger 37c holding fitting member 37d return spring

Claims (9)

[Claims] 1. A bass reproducing speaker device comprising a speaker unit, means for providing a negative stiffness to a vibration system of the speaker unit, and a cabinet for accommodating the speaker unit. Detecting means for generating a corresponding electric signal;
The power amplifier for driving the speaker unit is provided with a feedback circuit for feeding back the electric signal from the detection means to the power amplifier for reproducing the source signal, and the power amplifier is biased in the displacement direction of the vibration system of the speaker unit in addition to the source signal power. A low-frequency sound reproduction speaker device, wherein electric power for correcting the noise is supplied to the speaker unit. 2. The low-frequency sound reproduction speaker device according to claim 1, wherein a movable magnet that moves together with the vibration system of the speaker unit, and a Hall element that detects the magnetism of the movable magnet are used as the detection means. . 3. A means for imparting negative stiffness to the vibration system of the speaker unit is compressed into a plurality of substantially central axis symmetrical portions between the center of the vibration system of the speaker unit and the vicinity of the outer periphery of the speaker unit. 3. A spring mounted and attached.
4. The bass reproduction speaker device according to claim 1. 4. A means for providing a negative stiffness to the vibration system of the speaker unit, comprising: a movable magnet moving together with the vibration system of the speaker unit; and a fixed means for applying a force in the vibration displacement direction of the speaker unit to the movable magnet. 2. A magnet as a magnet.
Or the low-frequency sound reproduction speaker device according to 2. 5. The low-frequency sound reproduction speaker device according to claim 1, further comprising means for holding a vibration system of the speaker unit near a center position in a displacement direction when not operating. 6. A self-holding solenoid is used as means for holding a vibration system of the speaker unit near a center position in a displacement direction when not operating.
4. The bass reproduction speaker device according to claim 1. 7. The self-holding solenoid according to claim 6, wherein an operating current of the self-holding solenoid is supplied via a capacitor, and a return current of the self-holding solenoid is supplied by discharging the capacitor. A bass reproduction speaker device. 8. The apparatus according to claim 1, further comprising: means for reducing a negative stiffness of the means for giving a negative stiffness to the vibration system of the speaker unit when the speaker unit is not operated.
5. The low-frequency sound reproduction speaker device according to any one of items 1 to 4. 9. The low-frequency sound reproduction speaker device according to claim 1, further comprising: means for varying a stiffness of a means for giving a negative stiffness to the vibration system of the speaker unit.