JPH01296798A - Driver and its control information container - Google Patents

Abstract

PURPOSE:To easily and surely set a characteristic value such as an output impedance of a driver to a proper value by separating a revision setting means of a transmission characteristic of a feedback circuit into a main body section and a control information container. CONSTITUTION:Any desired speaker system among speaker systems 21A, 21B,... is connected to an output terminal 33 of a main body internal circuit section 31 by a connection cord 18. Then a cartridge is (any of cartridge 15A for speaker 21A, cartridge 15B for speaker 21B,...) corresponding to a connected speaker system 21 (any of systems 21A, 21B,...) is set to a driver main body 10 to connect a connector 12 of a main body circuit board 13 and a connector 16 of a cartridge circuit board 17. Thus, an equalizer circuit 34 whose drive characteristic value is set to a proper value to the speaker system 21 and a drive circuit 20 including a negative impedance circuit 60 are formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention drives an electroacoustic transducer such as a speaker system constituting a speaker system so as to improve the output characteristics of the transducer. The present invention relates to a drive device that is compatible with multiple types of systems, and a control information storage body for easily changing or setting the drive characteristics of this drive device.

[Prior Art] Conventionally, a power amplifier with an output impedance of substantially O has been generally used as a drive device for driving a speaker unit incorporated in a speaker system.

Further, conventional speaker systems are configured to exhibit the best acoustic output characteristics when driven by a so-called constant voltage using a power amplifier whose output impedance is substantially O.

FIG. 10 shows a cross-sectional view of a conventional closed-type speaker system. As shown in the figure, a hole is made in the front of a sealed box (cabinet) 1, and an electrodynamic speaker unit 3 having a diaphragm 2 is attached to the hole.

The resonant frequency f of this closed speaker system. 0 is foc-fo (1+Sc/so) "'"
It is expressed as (1). Moreover, the Q value Qoc of this speaker system is Qoc=Qo (1+Sc/So)""" (
2). Here, fo and Qo represent the lowest resonant frequency and Q value of the electrodynamic speaker unit 3, that is, the resonant frequency and Q value when this speaker unit 3 is attached to an infinite plane baffle. Also, So
is the equivalent stiffness of the vibration system, and Sc is the equivalent stiffness of the cabinet 1.

In this closed speaker system, fO
c is a measure of the bass reproduction limit of the uniform reproduction band, that is, the minimum reproduction frequency. Moreover, Qoc is the resonance frequency f. C
It is related to the frequency characteristic curve around f, and if it is too high, the characteristic curve will be this f. If it is too low, it will rise too much around C, and if it is too low, it will fall too much, both of which will worsen the flatness of the frequency characteristics. 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 figure, a hole is made in the front of a cabinet 1 and an electrodynamic speaker unit 3 having a diaphragm 2 is installed.
Further, a resonance boat (bass reflex boat) 8 having a sound path 7 is provided below, and the resonance boat 8 and the cabinet 1 constitute 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 boat 8. and,
This resonance frequency fOP is fOP=c (A/jZV)”
' /2π '' (3). Here, C
is the speed of sound, A is the cross-sectional area of the sound path 7, 1 is the length of the sound path 7, and ■ is the volume of the cabinet 1. Here, in a bass reflex type speaker system that follows normal basic settings, the resonance frequency f. The lowest resonant frequency f of the speaker unit 3 when P is installed in the bass reflex cabinet l
. It is set slightly lower than c+ (~foc).

and the resonance frequency f. At frequencies higher than P,
The sound pressure from the rear surface of the diaphragm 2 becomes out of phase at the sound path 7, and therefore, at the front of the cabinet 1, the sound directly radiated from the front surface of the diaphragm 2 and the sound from the resonance boat 8 end up being in phase. In-phase addition is performed to intensify the sound pressure. In other words, by this in-phase addition, the lowest resonant frequency as a system becomes the resonant frequency f of the resonator. According to the optimally designed bass reflex speaker system, the frequency characteristics of the output sound pressure are adjusted to the minimum resonance frequency f of the speaker unit 3.
. C' or less, as shown by the two-dot chain line in Figure 12, the −-like reproduction range can be extended to an infinite plane baffle (solid line).
It can be expanded more than a sealed baffle (dotted chain line).

Incidentally, in the above equations (1) and (2), the equivalent stiffness SC is inversely proportional to the volume (■) of the cabinet 1.

Therefore, when the speaker system shown in FIGS. 10 and 11 is driven at a constant voltage, the frequency characteristics, especially the low frequency characteristics, are affected by the volume V of the cabinet 1, and the speaker system as shown in FIGS. 1. Furthermore, there is a disadvantage that it is difficult to downsize the speaker system.

Furthermore, for example, in order to compensate for the reduced bass reproducing ability due to the miniaturization of the cabinet, it is possible to boost the bass using tone control, GRACO, or a dedicated equalizer on the driving amplifier side, as shown in FIG. This is difficult to reproduce f. This is a method of increasing the sound pressure by increasing the size of the input terminal for the band below C.

In this way f. It is possible to raise the sound pressure below C, but f due to the increased Qoc caused by placing it in a small cabinet. Deterioration of transient response at 0 and also Q. f due to 0 or high. Since the negative effects caused by the increased Qoc, such as sudden phase changes in C, cannot be removed, the effect is simply to increase the sound pressure of bass sounds, and it is not possible to remove the negative effects caused by the increased Qoc. f using a cabinet with ■. This has the disadvantage that it is not possible to obtain sound quality equivalent to that of a speaker system with an appropriate C1Qoc value.

Furthermore, in a bass reflex type speaker system as shown in FIG. 11, if the frequency characteristics when driven at a constant voltage are to be flattened, the Q value of the speaker unit 3 when installed in a bass reflex type cabinet, for example, is
'=1/! Finally, the resonant frequency is f. p' = foc
/Speaker unit 3
Characteristic value of (fo.

QO), the volume V of the cabinet 1, the dimensions (A, n) of the resonant boat 8, etc. must be matched to a high degree, which is disadvantageous in that there are many design restrictions. here,
Q oc' and f. C゛ is approximately the above (1)
and Q according to equation (2). C and f. It can be obtained as C.

Figure 14 shows the patent application filed earlier by the applicant in 1986-33.
4262 shows the negative impedance generation circuit shown in No. 4262. A driving method (hereinafter referred to as negative resistance) uses such a negative impedance generation circuit as a driving device of a speaker system, and includes a negative resistance -R8 in the output impedance to reduce or nullify the voice coil resistance RV of the speaker. □According to the drive), the output impedance is 0.
The above-mentioned Q is higher than when driving at a constant voltage with a power amplifier. c.
, Qoc' can be reduced and Qop can be increased, which is effective in downsizing the speaker system and improving the acoustic output characteristics.

However, in the amplifier of this prior application using the negative resistance drive method currently in practical use, there is a one-to-one correspondence between the amplifier and the speaker system, so one type of amplifier cannot be used to drive multiple types of speaker systems. There was an inconvenience that it was not possible.

The reason for this is as follows. That is, in the negative resistance drive method, the negative resistance value -RO must be set to R8 times RV with respect to the voice coil resistance RV of the speaker, and furthermore, the speaker system is driven according to this negative resistance value -Ro. Since the frequency characteristics of the output sound pressure from the filter change, it is necessary to not only control the negative resistance value -Ro but also to compensate for the accompanying change in frequency characteristics.

However, although it is currently possible to perform equalization tailored to a music source using a graphic equalizer or the like, it is actually relatively difficult for general users to perform appropriate equalization. Therefore, it is considered almost impossible for general users to appropriately control both the negative resistance value -Ro and the associated frequency characteristic change compensation settings. For this reason, the negative resistance drive type amplifier of the earlier application is one-on-one with the speaker system.
Only compatible versions are currently in use.

[Problems to be Solved by the Invention] An object of the present invention is to be able to drive an electroacoustic transducer by improving the output characteristics of the transducer, and to easily accommodate multiple types of transducers. An object of the present invention is to provide a drive device and a control information storage body used to make the drive device compatible with a plurality of types of converters.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides feedback to the input or output of the electroacoustic transducer to cancel the reaction from the surroundings to the vibrating body of the electroacoustic transducer. The present invention is characterized in that it includes a drive circuit that drives the converters, and that parts of the drive circuit that store control information corresponding to various types of converters are separated and configured as a control information storage body.

[Operation] The driving device of the present invention drives the electroacoustic transducer so as to cancel out the reaction from the surroundings to the vibrating body of the electroacoustic transducer. Such drive devices include a negative impedance generation circuit that equivalently generates a negative impedance component (-Zo) in the output impedance, and a motion drive device that responds to the movement of a vibrating body (for example, the diaphragm 2 in Fig. 10). A known circuit such as a motional feedback (MFB) circuit that detects a signal by some method and provides negative feedback to the input terminal can be used.

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

That is, to explain the case where it is applied to a speaker system with a resonant boat which is similar in shape to a bass reflex type speaker system as shown in FIG. 11, the equivalent stiffness SC of the cabinet and the unit side resonance &(So and m.

) with Q. By reducing Co or O,
The frequency fO when the diaphragm can be driven in a highly damped state and the cabinet is miniaturized as shown in Figure 13
The sound quality can be improved by suppressing the peak at "c". In addition, Qop can be set to a relatively large value regardless of the above-mentioned Q. In particular, the low-frequency characteristics can be improved.The closed type speaker system as shown in FIG. 1
The boat's equivalence quality imP is in the state ■. therefore,
Even in a closed speaker system, by driving with the drive device of the present invention, the Qoc is reduced or becomes zero, and by combining this with the increase/decrease of the human input signal level of the drive device, the lowest reproduction frequency can be lowered and the sound quality can be improved. be able to. Further, the cabinet can be made smaller without impairing the acoustic output characteristics. In this invention, the part to be adjusted according to the type of electroacoustic transducer is further separated from the main body to form a control information storage body, and this storage body is attached to the electroacoustic transducer to be driven by the drive device of the present invention. By selecting a corresponding value and setting it in the main body, an appropriate output impedance etc. can be set for the converter. Further, equalizer characteristics can also be set by the storage body as required.

[Effect] Therefore, according to the present invention, a general user can change the output impedance, etc. of this drive device by simply selecting the control information storage body corresponding to the converter to be driven by this drive device and coupling it to the drive device. The characteristic value of can be easily and reliably set to an appropriate value.

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

Further, while a normal equalizer mainly controls frequency characteristics, the present invention controls the amount of feedback for the motional component, so it is possible to actively control the Q value.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the 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, inside the case ll of the drive device 10,
A connector (jack) 12 and an in-body circuit board 13 having an in-body circuit section 31 shown in detail in FIG. 2 are stored.

Cartridge 15 (15A, 15B,...)
are each speaker system 21 (21A, 21B), for example with a resonance boat, to be connected to this drive device.

Connectors (plugs) 16 are prepared corresponding to each of the connectors 12 and can be connected to the respective connectors 12.
Further, an in-cartridge circuit board 17 provided with an in-cartridge circuit section 32 shown in detail in FIG. 2 is housed. The connectors 12 and 16 include an internal circuit board 13.
and the circuit board 17 in the cartridge, four contacts are provided for connecting the power supply VCC1, the electric signal EIN, the negative side terminal (-) of the speaker, and the common line GND.

When using this drive device, connect any desired one of the speaker systems 21A, 21B, . (2
1A, 21B, ...) corresponding to the cartridge 15 (cartridge 15A for speaker 21A).
, speaker 21B cartridge 15B, . . . ) is set in the drive device main body 10, and the connector 12 of the main body circuit board 13 and the connector 16 of the cartridge internal circuit board 17 are connected. As a result, the drive circuit 20 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 20 of FIG. 2, the negative impedance circuit 60 includes an amplifier circuit 61, a resistor Rs, and a feedback circuit 63.
It consists of

In this negative impedance circuit 60, the output of the amplifier circuit 61 with a gain of A is connected to the output terminal 33 and the connection cord 1.
8 to the speaker unit 3 as a load.

Then, the current (2) flowing through the speaker unit 3 is detected by the load current detection resistor R5, and is positively fed back to the amplifier circuit 61 via the feedback circuit 63 with the transfer gain β. In this way, the output impedance Z of the drive circuit 20, that is, the drive device of FIG. is obtained as RO=R3(I Aβ). From this equation, if Aβ>1, Ro becomes an open stable negative resistance.

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

FIG. 3 shows an electrical equivalent circuit of a portion consisting of the speaker system with resonance boat 21 shown in FIG. 1 and the negative impedance circuit 60 shown in FIG. Here, the parallel resonant circuit Z
1 is based on the equivalent motional impedance of the speaker unit 3, ro represents the equivalent resistance of the vibration system, so represents the equivalent stiffness of the vibration system, and m□ represents the equivalent stiffness of the vibration system. Further, the series resonant circuit Z2 is based on the equivalent motional impedance of the Helmholtz resonator constituted by the resonant boat 8 and the cabinet 1, rc indicates the equivalent resistance of the cavity of the resonator, and S
C denotes the equivalent stiffness of the cavity and r is the resonance boat 8
mp indicates the equivalent resistance of the resonance boat 8. In addition, A in the figure is a force coefficient, and when the speaker unit 3 is an electrodynamic direct radiation speaker, B
Assuming that is the magnetic flux density in the magnetic gap and 9°C is the total length of the voice coil conductor, A=BflV. Furthermore, Zv in the figure is the internal impedance (non-motional impedance) of the converter 3, and when the speaker unit 3 is an electrodynamic direct radiation speaker, it is mainly the resistance RV of the voice coil and includes a small amount of inductance. There is.

Next, the operation of the acoustic device having the configuration shown in FIGS. 1 and 2 will be explained.

When a drive signal is given to the speaker unit 3 from the drive circuit 30 having a negative impedance drive function, the unit 3 converts this into an electromechanical signal to reciprocate 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, disabled). Therefore, the unit 3 drives the diaphragm 2 in faithful response to the drive signal input to the drive circuit 30,
Furthermore, driving energy is independently applied to the Helmholtz resonator constituted by the resonance boat 8 and the cabinet 1. At this time, the front side of the diaphragm 2 (the right side in Figure 2) forms a direct radiating part for directly radiating sound to the outside, and the rear side of the diaphragm 2 (the left side in Figure 2) serves as a direct radiating part for directly radiating sound to the outside. ) constitutes a resonator drive section for driving a Helmholtz resonator consisting of a cabinet 1 and a resonance boat 8.

Therefore, sound is directly radiated from the diaphragm 2 as shown by the arrow a in the figure, and the air inside the cabinet 1 is resonated, so that the sound is directly radiated from the diaphragm 2 as shown by the arrow a in the figure. Sound of sufficient sound pressure is resonantly radiated from the opening of the boat 8). Then, by adjusting the air equivalent mass in the resonance boat 8 in the Helmholtz resonator, this resonance frequency f is adjusted. By setting P lower than the Helmholtz resonance frequency f op = f oc/ , fT in the system shown in Fig. 2, and setting the Q value to an appropriate level by adjusting the equivalent resistance of the resonance boat 8, an appropriate Under the condition that a level of sound pressure can be obtained, and further by appropriately increasing or decreasing the human signal level, it is possible to obtain the frequency characteristic of the sound pressure as shown by the solid line in FIG. 4, for example.

In FIG. 4, the two-dot chain line shows the frequency characteristics and impedance characteristics of the closed type speaker system, and the broken line shows the frequency characteristics and impedance characteristics of the bass reflex type speaker system.

Hereinafter, the effect when driving a speaker system using a Helmholtz resonator with negative impedance will be explained.

FIG. 5 is an electrical equivalent circuit when ZV −20=o in FIG. 3, that is, when the internal impedance (non-motional impedance) of the speaker unit 3 is equivalently completely nullified.

Here, the coefficients attached to the values of each element are omitted.

The following is clear from this equivalent circuit.

First, the parallel resonant circuit Z1 based on the equivalent motional impedance of the speaker unit 3 is short-circuited at both ends with zero impedance in terms of alternating current. Therefore, this parallel resonant circuit Z1 has a Q value of O, and is no longer substantially a resonant circuit. That is, in this speaker unit 3, the concept of the lowest resonant frequency that existed when the speaker unit 3 was simply attached to a Helmholtz resonator no longer exists.

Hereinafter, the lowest resonant frequency f of the speaker unit 3.

When we say "considerable amount," we are merely referring to the above-mentioned concept, which has essentially been invalidated. In this way, the unit resonance system (parallel resonance circuit) Z+ substantially ceases to be a resonance circuit, and as a result, the Helmholtz resonance system (series resonance circuit) Z2 becomes the only resonance system in this acoustic device.

In addition, as a result of the vibration system becoming substantially no longer a resonant circuit, the speaker unit 3 responds linearly to the human power drive signal in real time, and faithfully converts the human power electric signal (drive signal EO) into an electric signal without any transient response. Mechanical conversion, diaphragm 2
will be displaced. In other words, it is in a complete braking state (so-called speaker dead state). In this state, the output sound pressure frequency characteristic near the value equivalent to the lowest resonance frequency fo of this speaker is 6 dB/oct. On the other hand, the characteristics of normal voltage drive state are 12dB
/oct.

On the other hand, the series resonant circuit Z based on the equivalent motional impedance of the Helmholtz resonator is the drive signal source E.

Since it is connected with zero impedance to the parallel resonant circuit Z1, there is no longer a mutually dependent relationship between the parallel resonant circuit Z1 and the series resonant circuit Z2, and the parallel resonant circuit Z1 and the series resonant circuit Z2 coexist independently. Therefore, the volume of the cabinet 1 (inversely proportional to Sc) and the shape and dimensions of the resonance boat 8 (proportional to mp) do not affect the direct radiation characteristics of the speaker unit 3, and also the resonance frequency and Q of the Helmholtz resonator. The value is also 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, the series resistance of the series resonant circuit Z2 is only r(+rp, and these are usually sufficiently small values, so this series resonant circuit Z2,
That is, the Q value of the Helmholtz resonator can be set sufficiently high.

From another perspective, the unit vibration system is no longer effectively a resonant system, so it is displaced according to the human power of the drive signal,
It is substantially unaffected by external forces, especially atmospheric reactions due to the equivalent stiffness Sc of the cabinet. Therefore, the diaphragm 2 of the speaker unit 3 becomes a wall isometrically when viewed from the cabinet side, and the existence of the speaker unit 3 when viewed from the Helmholtz resonator is nullified. therefore,
The resonant frequency and Q value as a Helmholtz resonator are:
Regardless of the non-motional impedance of the speaker unit 3, the Q value is maintained at a sufficiently large value even when this resonant frequency is set to a frequency where the resonance Q value would be extremely small in a normal drive system. be able to. Furthermore, the Helmholtz resonance system can be called a virtual speaker that emits sound completely independently of the unit vibration system. Although this virtual speaker is realized with a small diameter equivalent to the diameter of a boat, its bass reproduction ability corresponds to an extremely large diameter speaker in real life.

Comparing the above with the conventional method in which the bass reflex type speaker system shown in FIG. Moreover, the resonant frequency and Q value of each resonant system were closely dependent on each other. For example, if the boat is made longer or thinner (increases mp) in order to lower the resonant frequency of the Helmholtz resonance system Z2, the Q value will become higher in the unit vibration system Z, and lower in the Helmholtz resonance system Z2. If the volume of the cabinet is reduced (SC becomes large), even if the resonant frequency of the Helmholtz common mouth 1 system Z2 is kept constant by making the boat longer or thinner, the unit vibration system Z,
In the Helmholtz resonance system Z2, the Q value and resonance frequency became high, and the Q value became even lower in the Helmholtz resonance system Z2. That is,
The output sound pressure frequency characteristics of a speaker system are closely related to the characteristics of the speaker unit, the volume of the cabinet, and the dimensions of the boat, so advanced design technology is required to match these, and the output sound pressure It is generally considered impossible to downsize a cabinet (system) without impairing frequency characteristics, especially low-frequency characteristics, or simply expand the sound reproduction band of an existing system without impairing sound quality or other characteristics. It was getting worse. Furthermore, the relationship between the frequency in a band lower than the resonant frequency for in the Helmholtz resonance system Z2 and the resonant acoustic radiation ability is that, from the perspective of the sound pressure level, 12 d
If B/oc is reduced at a certain rate and the resonant frequency is set extremely low compared to the basic idea of a bass reflex speaker system, it becomes extremely difficult to make corrections due to increases or decreases in the human signal level.

As mentioned above, the drive device of this embodiment drives the speaker system using Helmholtz resonance with negative impedance, so the characteristics and dimensions of the unit vibration system and Helmholtz resonance system of the system can be set independently. ,
Moreover, even if the resonant frequency of the Helmholtz resonance system is set low, the Q value and bass reproduction ability can be maintained high, and the resonator driving ability of the unit vibration system is also strong (
6dB10at), so the waviness of the frequency characteristic is
This feature allows correction to be made by increasing or decreasing the input signal level, for example by increasing or decreasing the level of normal sound quality adjustment, and for this reason, it is possible to downsize the cabinet and configure the speaker system without compromising frequency characteristics or sound quality. In addition, it is possible to improve the sound quality of an existing speaker system compared to conventional constant voltage drive, or to easily expand the sound reproduction band, especially the bass side.

In addition, in the above description, only the case where ZV −20=Q was explained, but the present invention also includes the case where Z v Z o > O as long as −Z o <0. In this case, the characteristic values of the unit vibration system and the Helmholtz resonance system, etc., will be values between the case of the above Zv Zo''O and the case of the conventional constant voltage drive system, depending on the value of the impedance ZV-20.

Therefore, by actively utilizing this property, for example, instead of adjusting the Q value of a Helmholtz resonance system by adjusting the boat diameter or inserting a mechanical Q damper such as glass wool or felt into the cabinet. , negative impedance −Z. This can be done by adjusting.

In addition, in this case, it was extremely difficult for general users to properly set the output impedance and increase/decrease the input signal level using variable resistors, changeover switches, etc.; however, as shown in Figure 1, By setting or replacing the cartridge, the transfer characteristics of the feedback circuit 63 are set or changed to set an appropriate negative impedance value -2° etc. for the system to be driven. Setting the value has become extremely easy.

Note that the closed type speaker system is a speaker system with a resonance boat described above with the resonance boat removed.
Therefore, in the equivalent circuits of Figs. 3 and 5, the equivalent mass mp of the resonant boat is (1), that is, the capacitor mP
/A2 can be understood as being short-circuited. In other words, even in a closed speaker system, by driving a power amplifier with negative impedance in its output impedance and increasing or decreasing the human input signal level of this power amplifier, the lowest resonant frequency of the speaker unit can be achieved regardless of the cabinet volume. f. Relatively high quality reproduction can be achieved up to the vicinity of the equivalent value.

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

The circuit shown in the figure outputs the output of an amplifier 61 with a gain of A to a speaker 3.
The load ZL is given by Then, the current IL flowing through the load ZL is detected and positively fed back to the amplifier circuit 61 via a feedback circuit 63 with a transfer gain β. In this way, the output impedance Z of the circuit. is, Zo=Z, (1-Aβ)...
... is obtained as (4). From this equation (4), Aβ
〉If 1, then Z. becomes an open stable negative impedance. Here, %ZS is the impedance of the sensor that detects the current.

Therefore, in the circuit shown in FIG. 6, by appropriately selecting the type of impedance Zs, a desired negative impedance component can be included in the output impedance. For example, when detecting the current ■ by the voltage across the impedance Zs, the impedance ZS
If the resistance is R3, the negative impedance component becomes a negative resistance component, if the inductance Ls is a negative inductance component, and if the capacitance C5 is a negative capacitance. Further, by using an integrator in the feedback circuit 63 and integrating and detecting the voltage across the inductance Ls as the impedance Zs, a negative impedance component can be made into a negative resistance component. Even if the voltage across the capacitance C9 serving as the impedance z5 is differentiated and detected using , the negative impedance component becomes a negative resistance component.

Tit? As the a detection sensor, in addition to these impedance elements Rs, Ls, Cs, etc., it is also possible to use current probes such as C, T, and Hall elements.

A concrete example corresponding to such a circuit is, for example,
-51771 etc.

Furthermore, it is also possible to perform current detection on the non-grounded side of the speaker 3. A specific example of such a circuit is shown in, for example, Japanese Patent Publication No. 54-33704. Figure 7 is BTL
Although this is an example of connection, it is easy to apply to the circuit shown in FIG. 64 in FIG. 7 is an inverting circuit.

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

The output impedance Z0 in the amplifier of FIG. 8 is Zo −Rs (1−Rb /R−)=0.22 (
1-30/1.6) = -3.9 (Ω). In addition, in FIG. 8, a portion 32 surrounded by a dotted line
corresponds to the cartridge internal circuit 32 in FIG.

[Modifications of Embodiments] Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented with appropriate modifications.

For example, in the above case, the equalizer circuit 34 and the feedback circuit 63 are included in the cartridge 15 as a control information storage body.
Although an example has been shown in which the entire drive unit 63 is stored separately from the drive device main body 10, at least the feedback circuit 63 is included in the control information storage body.
It is within the scope of the present invention as long as it includes a portion sufficient to change or set the feedback characteristics of the device.

Moreover, although the example in which analog circuit information is stored as control information has been described above, this control information may be digital data.

In this case, for example, digital filters are used as the equalizer circuit 34 and the feedback circuit 63, and an A/D converter is provided between the feedback circuit 63 and the current detection element Z3 to digitize the output of the detection element Zs. Further, as the control information medium, a ROM, a magnetic field, a punch card, or the like can be used instead of the analog circuit in the above-described embodiments. Further, when a card is used as the medium, a card reader is provided in place of the connector 12, 16, and a data storage RAM or the like is provided inside.

Further, the cartridges 15A, 15B, ... are the 9th cartridges.
As shown in the figure, one speaker system e.g. 21A
Multiple types of different control information corresponding to 15A-1, 15A
-2, etc., and set the characteristics such as the output impedance of the drive device according to the type of speaker system and the music to be generated, such as jazz, classical, etc. It can also be configured as 9th
In the figure, (a) shows the frequency characteristic of the sound pressure output in a constant voltage drive state, and (b) shows the frequency characteristic of the sound pressure output when the characteristic value of negative impedance drive is set for each music.

Further, the drive circuit may be one that drives the vibrating body of the electroacoustic transducer so as to cancel out the reaction from the surroundings, and may be, for example, a so-called MFB circuit as disclosed in Japanese Patent Publication No. 58-31156. Good too.

Furthermore, by giving the output impedance a frequency characteristic, it is possible to improve the degree of freedom in setting Qoc', Qop, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic external view showing the basic configuration of a driving device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of the circuit configuration of the driving device shown in FIG. 1, and FIG. 3 is a diagram similar to that shown in FIG. 1. and an electrical equivalent circuit diagram of the acoustic device in FIG. 2, FIG. 4 is a sound pressure frequency characteristic diagram of the sound emitted from the acoustic device in FIGS. 1 and 2, and FIG. 6 and 7 are basic circuit diagrams of a circuit that generates negative impedance. Figure 8 is a specific circuit diagram of negative resistance drive. Figure 9(a)
(b,) is an explanatory diagram showing a modification of the drive device in Fig. 1; Fig. 10 is a sectional view showing the configuration of a conventional closed type speaker system; Fig. 11 is a configuration of a conventional bass reflex type speaker system. FIG. 12 is an explanatory diagram of the sound pressure characteristics of the speaker system shown in FIGS. 10 and 11. FIG. An explanatory diagram of the circuit and frequency characteristics when driven by voltage, and FIG. 14 are basic configuration diagrams of the negative impedance generating circuit according to the prior application. 1: Cabinet, 2: Photographic board, 3: Speaker unit, 8: Resonance boat, 10: Drive unit body, 12, 16: Connector, 15A, 15B, ・
. . .: cartridge, 21A, 21B, varnish beaker system, 30: drive circuit, 31: circuit within main body, 32: circuit within cartridge, 34: equalizer circuit, 60: negative impedance generation circuit.

Claims (5)

[Claims] (1) A power amplifier that supplies driving power to an electroacoustic transducer, and a feedback circuit that detects the input or output of the transducer and transmits it to the input side of the amplifier, In a drive device including a drive circuit that drives the vibrating body so as to cancel a reaction from the surroundings, the feedback circuit has a change setting means for changing or setting a transfer characteristic of the feedback circuit, and the change setting means The means is separated into a main body connected to the amplifier and a control information storage body that stores control information for setting the transfer characteristic and is configured to be separable and connectable to the main body. A drive device characterized by: (2) The drive device according to claim 1, wherein the electroacoustic transducer is a speaker system for reproducing music, and the control information storage body stores a plurality of pieces of control information corresponding to the types of music. . (3) The invention further comprises a frequency characteristic correction circuit that can be set to a frequency characteristic that is complementary to the frequency characteristic of the output sound pressure of an electroacoustic transducer that is connected to the front stage of the power amplifier and is to be driven. Drive device. (4) The drive device according to claim 3, wherein the control information storage further stores second control information for changing or setting the frequency characteristic of the frequency characteristic correction circuit. (5) The control information storage body according to claim 1, 2 or 4.