JPH0728474B2 - Drive device and control information storage body thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention drives an electroacoustic transducer such as a speaker unit that constitutes a loudspeaker system so as to improve the output characteristics of the transducer, and a plurality of electroacoustic transducers. The present invention relates to a drive device adapted to various types of systems and a control information storage body for easily changing or setting drive characteristics of the drive device.

[Prior Art] Conventionally, a power amplifier having an output impedance of substantially 0 has been generally used as a driving device for driving a speaker unit incorporated in a speaker system.
Further, the conventional speaker system is configured to exhibit the best acoustic output characteristic when being driven by a so-called constant voltage by such a power amplifier whose output impedance is substantially zero.

FIG. 10 shows a cross-sectional view of a conventional closed loudspeaker system. Enclosed box (cabinet) as shown
1 has a hole formed in the front surface thereof, and an electrodynamic speaker unit 3 having a diaphragm 2 is attached thereto.

The resonance frequency f _OC of this closed loudspeaker system is represented by f _OC = f _O (1 + S _C / S _O ) ^1/2 (1). Also, the Q value Q of this speaker system
_OC is represented by Q _OC = Q _O (1 + S _C / S _O ) ^1/2 (2). Here, f _O and Q _O represent the lowest resonance frequency and Q value of the electrodynamic speaker unit 3, that is, the resonance frequency and Q value when the speaker unit 3 is attached to an infinite plane baffle. Further, S _O is the equivalent stiffness of the vibration system, and S _C is the equivalent stiffness of the cabinet 1.

And in this closed speaker system, f _OC
Indicates the reproduction limit of low-pitched sound in the uniform reproduction band, that is, the minimum reproduction frequency. Q _OC is related to the frequency characteristic curve around the resonance frequency f _OC.
Lifted too much around _OC , too low too low,
In either case, the flatness of the frequency characteristic becomes poor. Q _OC is usually set to about 0.8 to 1.

FIG. 11 is a sectional view showing an example of the configuration of a conventional phase inversion type (bass reflex type) speaker system. In the speaker system shown in the same figure, a hole is made in the front surface of a cabinet 1 to mount an electrodynamic speaker unit 3 having a diaphragm 2, and a resonance port (bass reflex port) 8 having a sound path 7 is provided below it. , This resonance port 8 and cabinet 1
This is what constitutes a Helmholtz resonator. In this Helmholtz resonator, an air resonance phenomenon occurs due to the air spring of the cabinet 1 which is a closed cavity and the air mass in the sound path 7 of the resonance port 8. Then, the resonance frequency f _OP is obtained as f _OP = c (A / lV) ^1/2 / 2π (3). Here, c is the speed of sound, A is the cross-sectional area of the sound path 7, l is the length of the sound path 7, and V is the volume of the cabinet 1. Here, in the bass reflex type speaker system according to the normal basic setting, the resonance frequency f _OP is calculated from the lowest resonance frequency f _OC ′ (≈f _OC ) of the speaker unit 3 in the state of being incorporated in the bass reflex type cabinet 1. It is set slightly lower. Then, at a frequency higher than the resonance frequency f _OP, the sound pressure from the rear surface of the diaphragm 2 has an opposite phase at the sound path 7, and therefore, in front of the cabinet 1, there is a direct radiated sound from the front surface of the diaphragm 2. As a result, the sound from the resonance port 8 becomes in-phase, and is added in-phase to strengthen the sound pressure. That is, by this in-phase addition, the lowest resonance frequency of the system extends to the resonance frequency f _OP of the resonator, and according to the optimally designed bass reflex type speaker system, the frequency characteristic of the output sound pressure is changed to the lowest resonance frequency of the speaker unit 3. It can be extended to f _OC ′ or less, and as shown by the two-dot chain line in FIG. 12, the uniform reproduction range can be wider than that of the infinite plane baffle (solid line) or the closed baffle (one-dot chain line).

By the way, in the equations (1) and (2), the equivalent stiffness S _C is inversely proportional to the volume V of the cabinet 1. Therefore, when the speaker system as shown in FIGS. 10 and 11 is driven at a constant voltage, the frequency characteristic, particularly the low frequency characteristic is influenced by the volume V of the cabinet 1, and the low frequency characteristic is not impaired. There is an inconvenience that it is difficult to downsize the speaker system.

Also, for example, in order to compensate for the low-pitched sound reproduction ability that is reduced by miniaturizing the cabinet, as shown in FIG.
A method of boosting bass by using tone control, a graphic equalizer, or a dedicated equalizer on the drive amplifier side can be considered. This is a method of increasing the sound pressure by increasing the input voltage in the band below f _{OC where} reproduction is difficult. It is possible to raise the following sound pressure f _OC in this way, in the f _OC due to degradation and also Q _OC transient reactions at f _OC by elevated Q _OC by placed in small cabinet is high Since the adverse effects of high Q _OC , such as a sudden phase change, cannot be eliminated, it is only the effect of increasing the sound pressure of the bass, and f _OC , Q using a cabinet with an appropriate capacity V
There was the inconvenience that sound quality equivalent to that of a speaker system with an appropriate value for _OC could not be obtained.

Further, in the bass reflex type speaker system as shown in FIG. 11, if the frequency characteristics when driven at a constant voltage are to be flattened, for example, the Q value of the speaker unit 3 in the state of being incorporated in the bass reflex type cabinet is The resonance frequency It is necessary to highly match the characteristic values (f _O , Q _O ) of the speaker unit 3, the volume V of the cabinet 1, the dimensions (A, l) of the resonance port 8 and the like, such that There was an inconvenience that there were many restrictions. Here, Q _OC ′ and f _OC ′ can be approximately _calculated as Q _OC and f _{OC according} to the above equations (1) and (2).

FIG. 14 shows the negative impedance generating circuit shown in Japanese Patent Application No. 62-334262 (Japanese Patent Laid-Open No. 1-302997) previously filed by the present applicant. A driving method that uses such a negative impedance generation circuit as a driving device for a speaker system and reduces or invalidates the voice coil resistance R _V of the speaker by including a negative resistance −R _O in the output impedance (hereinafter, negative driving According to that sex resistor drive), the Q _OC than if constant voltage drive at the power amplifier output impedance 0, small Q _OC ', and it is possible to increase the Q _OP, miniaturization and sound of the speaker system Effective in improving output characteristics.

However, the negative resistance drive type amplifier currently in practical use in this prior application has a one-to-one correspondence between the amplifier and the speaker system, so that one type of amplifier should be used to drive a plurality of types of speaker systems. There was an inconvenience that I could not do it.

The reason for this is as follows. That is, in the negative resistance driving method, the negative resistance value −R _O must be set to R _O <R _V with respect to the voice coil resistance R _V of the speaker, and further according to the negative resistance value −R _O. Since the frequency characteristic of the output sound pressure from the speaker system driven by the electric field changes, it is necessary to compensate not only the negative resistance value -R _O but also the change in the frequency characteristic. However, at present, for example, equalizing according to a music source can be performed by a graphic equalizer or the like, but proper equalizing is relatively difficult for general users.
Therefore, to perform both the negative resistance value -R _O controls and the frequency characteristic change compensating setting associated therewith the suitability, for the general user is no longer considered nearly impossible. For this reason, only the negative resistance drive type amplifier of the above-mentioned prior application is currently put into practical use in correspondence with the speaker system.

[Problems to be Solved by the Invention] An object of the present invention is to be able to drive an electroacoustic transducer while improving the output characteristics of the transducer, and to easily cope with a plurality of types of transducers. It is an object of the present invention to provide a drive device and a control information container used for making the drive device compatible with a plurality of types of converters.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a signal corresponding to a drive current of an electroacoustic transducer is fed back to equivalently generate a predetermined negative impedance, and this transducer is provided with the negative impedance. With a drive circuit that drives this converter so as to cancel or suppress the reaction from the surroundings with respect to the vibrator of this converter by reducing or nullifying the inherent internal impedance,
This drive circuit is characterized in that a portion for storing control information corresponding to various converters is separated and configured as a control information storage body.

[Operation] The drive device of the present invention drives the converter so as to reduce or nullify the internal impedance specific to the electroacoustic transducer by the negative impedance and cancel the reaction of the transducer from the surroundings with respect to the vibrating body. As such a driving apparatus, it is possible to apply a negative impedance generating circuit for generating an equivalent negative impedance component in an output impedance (-Z _O).

In this way, by driving this transducer so as to cancel the reaction of the electroacoustic transducer against the vibrating body from the surroundings, as described above with respect to the prior application device of FIG. The drawbacks can be eliminated.

That is, the case of application to a speaker system with a resonance port, which is similar in shape to the bass reflex type speaker system as shown in FIG. 11, will be described. The equivalent stiffness of the cabinet S _C and the unit side resonance system (S _O and m _O ) And Q
_{By making OC} 'small or 0, the diaphragm can be driven in a high braking state, and the peak at frequency f _OC ' in the case of miniaturizing the cabinet as shown in FIG. Can be improved. Also, Q _OP
Can be set to a relatively large value irrespective of the Q _OC ′, the speaker system can be downsized, and the uniform reproduction band, especially the low-frequency characteristic can be improved. In addition,
The closed loudspeaker system as shown in FIG. 10 is in a state where the cross-sectional area A of the resonance port of the bass reflex loudspeaker system is 0, that is, the equivalent mass m _{P of the} resonance port is ∞. Therefore, even in a closed loudspeaker system, by driving with the drive device of the present invention,
_OC decreases or becomes 0, and by combining it with the increase / decrease in the input signal level of the driving device, the minimum reproduction frequency can be decreased and the sound quality can be improved. Further, the cabinet can be downsized without impairing the sound output characteristics.

In the present invention, further, a portion to be adjusted according to the type of the electroacoustic transducer is separated from the main body to form a control information storage body, and the storage body is used as an electroacoustic transducer to be driven by the drive device of the present invention. By selecting correspondingly and setting it in the main body, it is possible to set an appropriate output impedance or the like in the converter. And
Further, the equalizer characteristic can be set by the storage body if necessary.

[Effect] Therefore, according to the present invention, a general user only needs to select the control information storage body corresponding to the converter to be driven by the drive device and couple the control information storage body to the drive device. The characteristic value of can be easily and surely set to an appropriate value.

Further, since the drive device of the present invention can be made compatible with a plurality of types of converters only by exchanging the control information storage body, the user can select a desired one from the plurality of types of converters. Also, when replacing the converter,
If only the control information storage body is purchased, the drive unit main body can be used as it is, and the cost investment is small.

Further, although the normal equalizer mainly controls the frequency characteristic, in the present invention, since the feedback amount for the motional is controlled, the Q value can be actively controlled.

Furthermore, according to the present invention, the power amplification structure for driving the electroacoustic transducer is an analog circuit, and the control information is also composed of an analog element circuit. Therefore, mutual coupling is extremely easy.

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

FIG. 1 shows the external appearance and overall configuration of a drive device according to an embodiment of the present invention, and FIG. 2 shows the basic circuit configuration. In FIG. 1, a case 11 of a driving device 10 accommodates a connector (jack) 12 and an in-body circuit board 13 in which an in-body circuit portion 31 shown in detail in FIG. 2 is arranged. The cartridge 15 (15A, 15B, ...) Is prepared for each speaker system 21 (21A, 21B ,. A connector (plug) 16 connectable to 12 and an in-cartridge circuit board 17 provided with an in-cartridge circuit portion 32 shown in detail in FIG. 2 are stored. The connectors 12 and 16 are provided with four terminals for connecting the power supply V _CC , the electric signal input E _IN , the speaker negative side terminal (−), and the common line GND between the main body circuit board 13 and the cartridge circuit board 17. Contact points are provided.

When using this drive device, a desired one of the speaker systems 21A, 21B, ... Is connected to the output terminal 33 of the in-body circuit section 31 by the connection cord 18, and the connected speaker system 21 (21A , 21B, ...)
The cartridge 15 (either the speaker 15A cartridge 15A, the speaker 21B cartridge 15B, ...) Corresponding to is set in the drive device main body 10 and the connector 12 of the internal circuit board 13 and the connector 16 of the internal circuit board 17 of the cartridge 16 are connected. And connect. As a result, the drive circuit 30 including the equalizer circuit 34 and the negative impedance circuit 60 shown in FIG. 2 whose drive characteristic values are set to appropriate values for the speaker system 21 is formed.

In the drive circuit 30 of FIG. 2, a negative impedance circuit
60 is composed of an amplifier circuit 61, a resistor R _S, and a feedback circuit 63.

In the negative impedance circuit 60, the output of the amplifier circuit 61 having the gain A is given to the speaker unit 3 as a load via the output terminal 33 and the connection cord 18. And
This speaker unit 3 is connected to the load current detection resistor R _S.
The current I _L flowing in the amplifier is detected and positively fed back to the amplifier circuit 61 via the feedback circuit 63 having the transfer gain β. In this way, the output impedance Z _O of the drive circuit 30, that is, the drive device of FIG. 1 is obtained as R _O = R _S (1-Aβ). From this equation, if Aβ> 1, R _O becomes an open stable negative resistance.

FIG. 3 shows an electrical equivalent circuit of the configuration shown in FIGS. 1 and 2.

FIG. 3 is a speaker system with a resonance port shown in FIG.
21 shows an electrical equivalent circuit of a portion composed of 21 and the negative impedance circuit 60 shown in FIG. Here, the parallel resonance circuit Z ₁ is based on the equivalent motional impedance of the speaker unit 3, r _O represents the equivalent resistance of the vibration system, S _O represents the equivalent stiffness of the vibration system, and m _O represents the vibration system. The equivalent mass is shown. The series resonance circuit Z ₂ is based on the equivalent motional impedance of the Helmholtz resonator composed of the resonance port 8 and the cabinet 1, and r _C
Is the equivalent resistance of the cavity of the resonator, S _C is the equivalent stiffness of the cavity, r _P is the equivalent resistance of the resonance port 8, m _P
Indicates the equivalent mass of the resonance port 8. Further, A in the figure is a force factor, when the speaker unit 3 is dynamic conductivity type direct radiation speaker, the magnetic flux density in the magnetic gap is B, and the l _V a conductor the entire length of the voice coil A = Bl _V
Becomes Furthermore, Z _V in the figure is the internal impedance (non-motional impedance) of the converter 3, and when the speaker unit 3 is an electrodynamic direct emission speaker, it mainly serves as the resistance R _{V of the} voice coil, which causes a slight inductance. Contains.

Next, the operation of the acoustic device configured as shown in FIGS. 1 and 2 will be described.

When a drive signal is applied to the speaker unit 3 from the drive circuit 30 having a negative impedance drive function, the unit 3 electromechanically converts the signal to drive the diaphragm 2 back and forth (left and right in FIG. 2). The diaphragm 2 converts this reciprocating motion into mechanical sound. Here, since the drive circuit 30 has a negative impedance drive function, the internal impedance of the unit 3 is equivalently reduced (ideally invalidated). Therefore, the unit 3 faithfully responds to the drive signal input to the drive circuit 30 to drive the diaphragm 2 and is independent of the Helmholtz resonator constituted by the resonance port 8 and the cabinet 1. Give driving energy to. At this time, the front side of the diaphragm 2 (the right side in FIG. 2) forms a direct radiating portion for directly radiating sound to the outside, and the rear side of the diaphragm 2 (the left side in FIG. 2). ) Is a resonator driving unit for driving the Helmholtz resonator including the cabinet 1 and the resonance port 8.

Therefore, sound is directly radiated from the diaphragm 2 as indicated by an arrow a in the figure, and the air in the cabinet 1 is caused to resonate, so that a resonance radiating portion (resonance) is generated as indicated by an arrow b in the figure. Sound of sufficient sound pressure is resonantly radiated from the opening of the port 8. Then, by adjusting the air equivalent mass in the resonance port 8 in the Helmholtz resonator, this resonance frequency f _{OP is set} to the Helmholtz resonance frequency in the system of FIG. The input signal level is appropriately increased or decreased on condition that the Q value is set to an appropriate level by adjusting the equivalent resistance of the resonance port 8 to a lower level and a sound level of an appropriate level is obtained from the opening. By doing so, for example, the frequency characteristic of the sound pressure as shown by the solid line in FIG. 4 can be obtained. In FIG. 4, the chain double-dashed line shows the frequency characteristic and impedance characteristic of the closed loudspeaker system of FIG. 10, and the broken line shows the frequency characteristic and impedance characteristic of the bass reflex loudspeaker system of FIG.

Hereinafter, the operation when the speaker system using the Helmholtz resonator is driven by negative impedance will be described.

FIG. 5 is an electrical equivalent circuit when Z _V −Z _O = 0 in FIG. 3, that is, the internal impedance (non-motional impedance) of the speaker unit 3 is equivalently completely disabled. Here, the coefficient attached to the value of each element is omitted.

The following is clear from this equivalent circuit.

First, both ends of the parallel resonance circuit Z ₁ having the equivalent motional impedance of the speaker unit 3 are AC short-circuited with zero impedance. Therefore, the parallel resonant circuit Z ₁ has a Q value of 0 and is substantially no longer a resonant circuit. That is, in this speaker unit 3, the concept of the lowest resonance frequency, which is simply present when the speaker unit 3 is attached to the Helmholtz resonator, is no longer present. Hereinafter, when the amount equivalent to the minimum resonance frequency f _O of the speaker unit 3 is referred to, the above concept that has been substantially invalidated is merely called. As described above, as a result of the unit resonance system (parallel resonance circuit) Z ₁ being substantially not a resonance circuit, the Helmholtz resonance system (series resonance circuit) Z _{2 is the} only resonance system in this acoustic device.

Further, as a result of the vibration system being substantially a resonance circuit, the speaker unit 3 makes a linear response in real time to the drive signal input and does not make a transient response at all, and faithfully receives the input electric signal (drive signal E _O ). The electromechanical conversion is performed and the diaphragm 2 is displaced. That is, it is a complete braking state (so-called speaker dead state). In this state, the output sound pressure frequency characteristic near the lowest resonance frequency f _O equivalent value of this speaker is 6 dB / oct. On the other hand, the characteristic in the normal voltage drive state is 12 dB / oct.

On the other hand, since the series resonance circuit Z ₂ based on the equivalent motional impedance of the Helmholtz resonator is connected to the drive signal source E _O with zero impedance, there is no mutual dependence relationship with the parallel resonance circuit Z _1. , Parallel resonant circuit
Z ₁ and the series resonant circuit Z ₂ are independent and coexistent. Therefore, the volume of the cabinet 1 (inversely proportional to S _C ) and the shape and size of the resonance port 8 (proportional to m _P ) do not affect the direct radiation characteristics of the speaker unit 3, and the resonance frequency of the Helmholtz resonator. Also, the Q value is not affected by the equivalent motional impedance of the speaker unit 3. That is, the characteristic value of the Helmholtz resonator and the characteristic value of the speaker unit 3 can be set independently. Furthermore, since the series resistance of the series resonance circuit Z ₂ is only r _C + r _P , and these are usually sufficiently small values, the Q value of the series resonance circuit Z ₂ , that is, the Helmholtz resonator is set to be sufficiently high. can do.

From another point of view, the unit vibration system is not actually a resonance system, so it is displaced according to the drive signal input,
It is virtually unaffected by external forces, especially atmospheric reaction due to the equivalent stiffness S _C of the cabinet. Therefore, the diaphragm 2 of the speaker unit 3 becomes an equivalent wall when viewed from the cabinet side, and the existence of the speaker unit 3 when viewed from the Helmholtz resonator is nullified. Therefore, the resonance frequency and the Q value of the Helmholtz resonator do not exist in the non-motional impedance of the speaker unit 3, and this resonance frequency is the Q value of the resonance in the normal driving method.
Even when the frequency is set so that the value becomes extremely small, the Q value can be maintained at a sufficiently large value. Also,
The Helmholtz resonance system is a virtual speaker that emits acoustic waves independently of the unit vibration system. Although this virtual speaker is realized with a small diameter corresponding to the port diameter, it is equivalent to an extremely large diameter speaker as an actual speaker when viewed from its bass reproduction capability.

Comparing the above with the conventional system in which the bass reflex type speaker system of FIG. 11 is driven by an ordinary power amplifier, in the conventional system, as is well known, a plurality of resonances of the unit vibration system Z ₁ and the Helmholtz resonance system Z ₂ are known. The system existed, and the resonance frequency and Q value of each resonance system were closely dependent on each other.
For example, to make the resonance frequency of the Helmholtz resonance system Z ₂ lower, make the port longer or thinner (m _P becomes larger).
If, Q value in the unit vibration system Z ₁ is increased, to lower the Helmholtz resonance system Z _2, to reduce the volume of the cabinet and (S _C increases), or a longer port, thin to Helmholtz resonance Even if the resonance frequency of the system Z ₂ was kept constant, the unit vibration system Z ₁ had a high Q value and the resonance frequency, and the Helmholtz resonance system Z ₂ had a lower Q value. In other words, the output sound pressure frequency characteristics of the speaker system are closely related to the characteristics of the speaker unit, the volume of the cabinet, and the size of the port, so a sophisticated design technology is required to match them. It is generally impossible to miniaturize the cabinet (system) without damaging the sound pressure frequency characteristics, especially low-frequency characteristics, and to easily expand the sound reproduction band of the existing system without damaging other characteristics such as sound quality. Was considered. Also, the above Helmholtz resonance system Z ₂
The relationship between the frequency in the band lower than the resonance frequency f _OP and the resonant acoustic radiation capacity decreases from the sound pressure level at a rate of about 12 dB / oct with respect to the decrease in the frequency, and the resonance frequency becomes the bass reflex speaker. If it is set extremely low with respect to the basic idea of the system, it becomes extremely difficult to correct it by increasing or decreasing the input signal level.

As described above, the driving device of this embodiment is designed to drive the speaker system using Helmholtz resonance by negative impedance, so that the unit vibration system and the Helmholtz resonance system characteristics and dimensions can be independently set.
Moreover, even if the resonance frequency of the Helmholtz resonance system is set low, the Q value and bass reproduction ability can be kept high, and the resonator drive ability of the unit vibration system also becomes strong (6 dB / oct). It is possible to obtain the characteristic that the swell of the frequency characteristic can be corrected by increasing or decreasing the input signal level, for example, by increasing or decreasing the normal sound quality adjustment degree. Therefore, the speaker system can be downsized without reducing the frequency characteristic and the sound quality. Can be configured in a small size, while improving the sound quality of the existing speaker system compared with the conventional constant voltage drive, or the sound reproduction band,
In particular, the bass side can be easily enlarged and driven.

In the above description, only the case of Z _V −Z _O = 0 has been described, but the present invention also includes the case of Z _V −Z _O > 0 if −Z _O <0. In this case, the characteristic values of the unit vibration system and the Helmholtz resonance system are between the case of Z _V −Z _O = 0 and the case of the conventional constant voltage drive method according to the value of the impedance Z _V −Z _O. Becomes the value of. Therefore,
Using this property positively, instead of adjusting the Q value of the Helmholtz resonance system, for example, by adjusting the port diameter or inserting a mechanical Q damper such as glass wool or felt in the cabinet, This can be done by adjusting the sex impedance −Z _O.

Further, in this case, it is extremely difficult for a general user to appropriately set the output impedance and increase / decrease of the input signal level with a variable resistor, a changeover switch or the like, but as shown in FIG. Since the transfer characteristic of the feedback circuit 63 is set or changed by setting or replacing the cartridge to set an appropriate negative impedance value −Z _O or the like in the system to be driven, the negative impedance value −Z _O Setting to an appropriate value has become extremely easy.

The closed speaker system is the speaker system with the resonance port removed from the resonance port,
Therefore, in the equivalent circuits of FIGS. 3 and 5, the equivalent mass m _P of the resonance port can be grasped as ∞, that is, the capacitor m _P / A ² is short-circuited. That is, even in a closed speaker system, the output impedance is driven by a power amplifier that includes negative impedance,
And by increasing or decreasing the input signal level of the power amplifier, it is possible to realize a relatively high-quality reproduction of up to the minimum resonance frequency f _O equivalent value near the speaker unit regardless of the volume of the cabinet.

FIG. 6 shows a basic configuration of a negative impedance generating circuit for driving the vibrator with negative impedance.

The circuit of the figure applies the output of the amplifier 61 of gain A to the load Z _L by the speaker 3. And the current flowing in this load Z _L
I _L is detected and is amplified through the feedback circuit 63 of transfer gain β.
Positively feed back to 61. In this way, the output impedance Z _{O of the} circuit is obtained as Z _O = Z _S (1−Aβ) ... (4). If Aβ> 1 from this equation (4),
Z _O is an open stable negative impedance. here,
Z _S is the impedance of the sensor that detects the current.

Therefore, in the circuit of FIG. 6, a desired negative impedance component can be included in the output impedance by appropriately selecting the type of impedance Z _S. For example, in the case of detecting the current I _L by the voltage across the impedance Z _S is the impedance Z _S is the resistance R _S
Then, the negative impedance component becomes a negative resistance component, the inductance L _S becomes a negative inductance component, and the capacitance C _S becomes a negative capacitance. Further, the integrator used in the feedback circuit 63, it is possible to make the negative impedance component and negative resistance component by detecting and integrating the voltage across the inductance L _S as the impedance Z _S, further feedback circuit 63 using differentiator, negative impedance component be detected by differentiating the voltage across the capacitance C _S as the impedance Z _S becomes a negative resistance component. As the current detection sensor, it is possible to use a current probe such as a CT or a Hall element in addition to the impedance elements R _S , L _S , and C _S.

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

It is also possible to detect the current on the non-grounded side of the speaker 3. A concrete example of such a circuit is, for example, Japanese Patent Publication
54-33704, etc. FIG. 7 shows an example of BTL connection, but it is easy to apply it to the circuit of FIG. Reference numeral 64 in FIG. 7 is an inverting circuit.

FIG. 8 shows a specific circuit example of an amplifier including a negative resistance component in the output impedance.

The output impedance Z _O in the amplifier of FIG. 8 is Z _O = R _S (1−R _b / R _a ) = 0.22 (1-30 / 1.6) = − 3.9 (Ω). Further, in FIG. 8, a portion 32 surrounded by a dotted line corresponds to the in-cartridge circuit 32 in FIG.

[Modifications of the Embodiment] The present invention is not limited to the above-described embodiments, and can be modified and implemented as appropriate.

For example, in the above description, the example in which the entire equalizer circuit 34 and the feedback circuit 63 are stored separately from the drive device main body 10 in the cartridge 15 as the control information storage body is shown, but at least the feedback circuit 63 is stored in the control information storage body. It is within the scope of the present invention as long as a sufficient portion for changing or setting the feedback characteristic of is stored.

Further, as shown in FIG. 9, the cartridges 15A, 15B, ... Are provided with a plurality of types 15A-1, 15A-2 ,. The characteristics such as the output impedance of the device can be determined by the type of speaker system as well as the music to be generated, such as jazz,
It can also be configured to be set according to classic, etc. In FIG. 9, (a) shows the frequency characteristic of the sound pressure output in the constant voltage drive state, and (b) shows the frequency characteristic of the sound pressure output when the characteristic value of the negative impedance drive is set for each music. Show.

Furthermore, by giving the output impedance frequency characteristics, it is possible to improve the degree of freedom in setting Q _OC ′, Q _{OP and the} like.

[Brief description of drawings]

FIG. 1 is a schematic external view showing a basic structure of a driving device according to an embodiment of the present invention, FIG. 2 is an explanatory view of a circuit structure of the driving device of FIG. 1, and FIG. 3 is FIG. FIG. 4 is an electrical equivalent circuit diagram of the acoustic device shown in FIG. 2, FIG. 4 is a sound pressure frequency characteristic diagram of sound radiated from the acoustic device shown in FIGS. 1 and 2, and FIG. Equivalent circuit diagram when Z _V −Z _O = 0, FIGS. 6 and 7 are basic circuit diagrams of a circuit for generating negative impedance, and FIG. 8 is a specific circuit for driving negative resistance. FIGS. 9 (a) and 9 (b) are explanatory views showing a modified example of the drive device of FIG. 1, FIG. 10 is a sectional view showing the configuration of a conventional sealed speaker system, and FIG. FIG. 12 is a cross-sectional view showing the configuration of the bass reflex type speaker system, and FIG. 12 is an explanation of the sound pressure characteristics of the speaker system of FIGS. 10 and 11. Fig. 13 is an explanatory diagram of the circuit and frequency characteristics when a speaker unit attached to a small cabinet is driven at a constant voltage with a boosted bass signal, and Fig. 14 is a negative impedance generation according to the prior application. It is a basic block diagram of a circuit. 1: Cabinet, 2: Diaphragm, 3: Speaker unit, 8: Resonance port, 10: Drive unit, 12, 16: Connector, 15A, 15B, ‥: Cartridge, 21A, 21B, ‥: Speaker system, 30: Drive circuit, 31: Main body circuit part, 32: Cartridge internal circuit part, 34: Equalizer circuit, 60: Negative impedance generating circuit.

Claims (5)

[Claims] 1. A power amplifier for supplying drive power to an electroacoustic converter, and a signal corresponding to a drive current of the converter so that a predetermined negative output impedance is equivalently generated in the power amplifier. And a feedback circuit for positively feeding back to the input side of the amplifier, so that the internal impedance specific to the converter is reduced so as to cancel the reaction of the converter from the surroundings with respect to the vibrator. In the driving device which is invalidated and driven, the feedback circuit has a change setting means for changing or setting the positive feedback transfer characteristic of the feedback circuit, and the change setting means is a main body connected to the amplifier. And control information consisting of an analog element circuit having a predetermined gain characteristic for setting the positive feedback transfer characteristic, and configured to be separable and connectable to the main body. Driving apparatus characterized by being separated into a control information storage body. 2. The electroacoustic transducer is a speaker system for reproducing music, and the control information storage body stores a plurality of the control information corresponding to the type of the music. Drive. 3. A frequency characteristic correction circuit which is connected to the preceding stage of the power amplifier and which can set a frequency characteristic complementary to the frequency characteristic of the output sound pressure of the electroacoustic transducer to be driven. The drive device described. 4. The control information container further comprises an analog element circuit having a predetermined transfer characteristic for changing or setting the frequency characteristic of the frequency characteristic correcting circuit.
The drive device according to claim 3, wherein the control information of the drive device is stored. 5. The control information container according to claim 1, 2 or 4.