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JPH01296798

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DESCRIPTION JPH01296798
[0001]
[Industrial field of application] The present invention drives an electroacoustic transducer such
as a speaker system comprising a speaker system such as a caninite so as to improve the output
characteristics of the transducer, and supports multiple types of systems. The present invention
relates to an enabled drive unit and a control information storage unit for easily changing or
setting the drive characteristic of the drive unit. 2. Description of the Related Art Heretofore, as a
drive device for driving a speaker unit incorporated in a speaker system, generally, a power
amplifier having substantially O output impedance has been used. Also, the conventional speaker
system is configured to exhibit the best acoustic output characteristics when so-called constant
voltage driving is performed by a power amplifier in which the output impedance is substantially
O. FIG. 10 shows a cross-sectional view of a conventional closed loudspeaker system. As shown, a
hole is made in the front of the sealed box (cabinet) 1, and an electrodynamic speaker unit 3
having a diaphragm 2 is attached thereto. Resonant frequency f of this enclosed speaker system.
0 is represented by foc-fo (1 + Sc / so) "'" (1). Further, the Q value Qoc of this speaker system is
expressed by Qoc = Qo (1 + Sc / So) "" "(2). Here, fo and Qo indicate the lowest resonance
frequency and the Q value of the electrodynamic speaker unit 3, that is, the resonance frequency
and the Q value when the speaker unit 3 is mounted on an infinite flat baffle. Further, So
indicates the equivalent stiffness of the vibration system, and Sc indicates the equivalent stiffness
of the cabinet 1. And in this closed type speaker system, fOc becomes a standard of the
reproduction limit of the low tone of the uniform reproduction band, that is, the minimum
reproduction frequency. Also, Qoc is a resonant frequency f. Related to the frequency
characteristic curve around C, if it is too high the characteristic curve is this f. If it is too high
around C and too low if it is too low, the flatness of the frequency characteristic is worse in either
case. The Qoc is usually set to about 0.8 to 1. FIG. 11 is a cross-sectional view showing an
example of the configuration of a conventional phase inversion (bass reflex) speaker system. In
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the speaker system of the figure, a hole is made in the front of the cabinet 1 to attach an
electrodynamic speaker unit 3 having a diaphragm 2, and a resonance boat (bass reflex boat) 8
having a sound path 7 is provided below it. The Helmholtz resonator is composed of the
resonance boat 8 and the cabinet 1.
In this Helmholtz resonator, a resonance phenomenon of air is caused by 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 calculated | required as fOP = c (A / jZV) "'/ 2 (pi)" (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 the bass reflex type speaker system
according to the normal basic setting, the resonance frequency f. The lowest resonance
frequency f of the speaker unit 3 in the state where P is incorporated in the bass reflex type
cabinet l. It is set slightly lower than c + (~foc). And the resonant frequency f. At frequencies
higher than P, the sound pressure from the rear surface of diaphragm 2 is in antiphase at sound
path 7, so that in front of cabinet 1, the direct radiation from the front surface of diaphragm 2
and the sound from resonance boat 8 Becomes in-phase as a result, and in-phase addition is
performed to intensify the sound pressure. That is, by this in-phase addition, the lowest
resonance frequency as a system is the resonance frequency f of the resonator. The lowest
resonance frequency f of the speaker unit 3 is the frequency characteristic of the output sound
pressure according to the bass reflex type speaker system which extends up to P and is optimally
designed. It can be extended to C 'or less, and as shown by a two-dot chain line in FIG. 12, the like reproduction range can be extended more than an infinite plane baffle (solid line) or a closed
baffle (one-dot chain line). By the way, in the equations (1) and (2), the equivalent stiffness SC is
inversely proportional to the volume 1 of the cabinet 1. Therefore, in the speaker system as
shown in FIGS. 10 and 11, when the constant voltage drive is performed, the frequency
characteristics, particularly the low frequency characteristics are affected by the volume V of the
cabinet 1, and the cabinet is obtained without losing the low frequency characteristics. 1, there is
a disadvantage that it is difficult to miniaturize the speaker system. Also, for example, in order to
compensate for the reduced bass reproduction capability due to the miniaturization of the
cabinet, as shown in FIG. 13, it is conceivable to boost the bass by tone control, a microphone or
a dedicated equalizer on the drive amplifier side. It is hard to reproduce f. Sound pressure can be
increased by enlarging the input terminal to a band of C or lower. F in this way. It is possible to
raise the sound pressure below C, but f due to Qoc raised by putting it in a small cabinet.
Deterioration of transient response at 0 and also Q. 0 or higher f.
57. An adverse effect due to an increase in Qoc, such as a sudden phase change at C, can not be
removed, so it is merely an effect of raising the sound pressure of the bass, and an appropriate
volume 57. Using a cabinet with ■ f. There is a disadvantage that the C1 Qoc can not obtain the
same sound quality as the speaker system with an appropriate value. Furthermore, in the bass
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reflex type speaker system as shown in FIG. 11, if it is intended to flatten the frequency
characteristics when driven at a constant voltage, for example, the Q factor of the loudspeaker
unit 3 in the state incorporated in the bass reflex type cabinet is Qoc. '= 1 /! Just the resonance
frequency f. The characteristic value (fo of the speaker unit 3) is set such that p '= f oc / 1. It is
necessary to match QO), the volume V of the cabinet 1, the dimensions (A, n) of the resonance
boat 8 and the like to a high degree, which is disadvantageous in that there are many design
restrictions. ここで、Qoc’およびf。 C ′ ′ is approximately Q according to the above
equations (1) and (2). Cおよびf。 It can be determined as C. FIG. 14 shows the negative
impedance generating circuit shown in Japanese Patent Application No. 62-334262 filed by the
present applicant. A driving method using such a negative impedance generating circuit as a
driving device for a speaker system and including negative resistance -R8 in the output
impedance to reduce or cancel voice coil resistance RV of the speaker (hereinafter referred to as
negative resistance According to □ drive), the above Q is more than the case of constant voltage
drive with a power amplifier with an output impedance of 0. c, Qoc 'can be made small and Qop
can be made large, which is effective in downsizing the speaker system and improving the sound
output characteristics. However, since the amplifier and the speaker system are in a one-to-one
correspondence with the amplifier of the negative resistance drive system of this prior
application currently used, one type of amplifier should be used to drive a plurality of speaker
systems. Was inconvenient. The reason is as follows. That is, in the negative resistance driving
method, the negative resistance value -RO must be R8 to RV relative to the voice coil resistance
RV of the speaker, and further, a speaker system driven according to the negative resistance
value -Ro In addition to the control of the negative resistance value -Ro, it is also necessary to
compensate for the change in the frequency characteristic associated with the change in the
frequency characteristic of the output sound pressure from the above. However, for example,
equalizing according to music sources is currently possible with a graphic equalizer or the like,
but appropriate equalization for general users is in a relatively difficult situation.
Therefore, it is considered that it is almost impossible for general users to properly perform both
the control of the negative resistance value -Ro and the accompanying setting of the frequency
characteristic change compensation. For this reason, only the amplifier of the negative resistance
drive system of the prior application corresponding to the speaker system is in practical use at
present. SUMMARY OF THE INVENTION It is an object of the present invention to drive an
electroacoustic transducer with improved output characteristics of the transducer, and to easily
cope with a plurality of transducers. It is an object of the present invention to provide a drive
device and a control information storage body used to make the drive device compatible with a
plurality of types of transducers. [Means for Solving the Problems] In order to solve the problems
described above, in the present invention, by feeding back the input or the output of the
electroacoustic transducer, the reaction from the surroundings to the vibrator of the transducer
is canceled. A drive circuit for driving the converter is provided, and in the drive circuit, a portion
for storing control information corresponding to various converters is separated to constitute a
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control information storage body. [Operation] The driving device of the present invention drives
this transducer so as to cancel the reaction from the surroundings to the vibrating body of the
electroacoustic transducer. As such a driving device, a motional impedance corresponding to the
movement of a negative impedance generating circuit or a vibrating body (for example, the
diaphragm 2 in FIG. 10) which generates a negative impedance component (-Zo) equivalently in
the output impedance. A known circuit such as a motional feedback (MFB) circuit which detects a
signal by any method and negatively feeds back to the input end can be used. Thus, by driving
this converter so as to cancel the reaction from the surroundings to the vibrating body of the
electroacoustic transducer, as described above for the prior-art apparatus of FIG. 14, the abovementioned in the conventional bass reflex type speaker system It is possible to eliminate the
drawbacks. That is, to explain the case where the present invention is applied to a speaker
system with a resonance boat similar in shape to the 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. )と
のQ。 By making Co small or O, the diaphragm can be driven in a high braking state, and the
peak at frequency fOc when the cabinet is miniaturized as shown in FIG. 13 is suppressed to
improve the sound quality. be able to. Also, said Qop Q. It can be set to a relatively large value
independently of Co, and the speaker system can be miniaturized and the low frequency
characteristics, particularly the low frequency characteristics, can be improved.
In the closed type speaker system as shown in FIG. 10, the cross section A of the resonance boat
of the bass reflex type speaker system is O, ie, the common port and the equivalent quality imP
of 1 boat are in. . Therefore, also in the closed type speaker system, the Qoc is reduced or 0 by
driving with the drive device of the present invention, and by combining with the increase and
decrease of the human power signal level of the drive device, the minimum reproduction
frequency is lowered and the sound quality is reduced. It can be improved. In addition, the
cabinet can be miniaturized without impairing the sound output characteristics. In the present
invention, further, the part 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 driven by the drive device of the present invention. By appropriately selecting and setting
in the main body, it is possible to set an appropriate output impedance or the like in the
converter. Further, the equalizer characteristic can also be set by the storage body as required.
[Effects] Therefore, according to the present invention, a general user can select the control
information storage body corresponding to the converter to be driven by this drive unit and
couple the same to the drive unit so that the output impedance of this drive unit etc. Can be
easily and reliably set to appropriate values. Further, since the drive device of the present
invention can be made compatible with a plurality of types of converters simply by replacing the
control information storage body, the user can select a desired one from the plurality of types of
converters. In addition, even when replacing the converter, if only the control information
storage body is purchased, the drive device main unit can be used as it is, and the cost
investment can be reduced. Furthermore, although the control of the frequency characteristic is
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mainly performed in the ordinary equalizer, in the present invention, since the feedback amount
of the motional component is controlled, the Q value can be actively controlled. Embodiments of
the present invention will be described below with reference to the drawings. FIG. 1 shows the
appearance and the overall configuration of a drive apparatus according to an embodiment of the
present invention, and FIG. 2 shows a basic circuit configuration. In FIG. 1, in the case 11 of the
drive device 10, there is stored an in-body circuit board 13 provided with a connector (jack) 12
and an in-body circuit portion 31 whose details are shown in FIG. The cartridge 15 (15A, 15B,...)
Should be connected to this drive, for example with each loudspeaker system 21 (21A, 21B) with
a resonance boat.
An in-cartridge circuit board 17 provided with an in-cartridge circuit portion 32 which is
prepared corresponding to each of the components and can be connected to the connector 12
and whose details are shown in FIG. Is stored. The connectors 12 and 16 are provided with four
contacts for connecting the power supply VCC1 electric signal human power EIN, the speaker
negative side terminal (-) and the common line GND between the circuit board 13 in the main
body and the circuit board 17 in the cartridge. ing. When using this drive device, the speaker
system 21 connected to any one of the speaker systems 21A, 21B,... Set the cartridge 15 (one of
the cartridge 15A for the speaker 21A and the cartridge 15B for the speaker 21B,...)
Corresponding to (one of 21A, 21B,...) To the drive device main body 10 The connector 12 of the
internal circuit board 13 and the connector 16 of the in-cartridge circuit board 17 are connected.
Thereby, a drive circuit 20 including the equalizer circuit 34 and the negative impedance circuit
60 shown in FIG. 2 in which the drive characteristic value is set to an appropriate value for the
speaker system 21 is formed. In the drive circuit 20 of FIG. 2, the negative impedance circuit 60
is composed of an amplifier circuit 61, a resistor Rs and a feedback circuit 63. In this negative
impedance circuit 60, the output of the amplification circuit 61 of gain A is applied to the
speaker unit 3 as a load via the output terminal 33 and the connection cord 18. Then, the load
current detection resistor R5 detects the current {circle over (1)} flowing through the speaker
unit 3 and positively feeds back to the amplifier circuit 61 via the feedback circuit 63 of the
transmission gain β. In this way, the output impedance Z of the drive circuit 20, ie the drive of
FIG. Is calculated as RO = R3 (I Aβ). From this equation, if Aβ> 1, then Ro is an open stable
negative resistance. FIG. 3 shows an electrical equivalent circuit of the configuration shown in
FIG. 1 and FIG. FIG. 3 shows an electric equivalent circuit of a portion composed of the speaker
system 21 with a resonance boat shown in FIG. 1 and the negative impedance circuit 60 shown
in FIG. Here, the parallel resonant circuit Z1 is based on the equivalent motional impedance of
the speaker unit 3, ro indicates the equivalent resistance of the vibration system, so indicates the
equivalent stiffness of the vibration system, and m □ indicates the equal mass of the vibration
system Is shown.
The series resonance circuit Z2 is based on the equivalent motional impedance of the Helmholtz
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resonator composed of the resonance boat 8 and the cabinet 1, rc denotes the equivalent
resistance of the cavity of the resonator, and SC is the equivalent of the cavity The stiffness is
indicated, r indicates the equivalent resistance of the resonance boat 8, and mp indicates the
equal alcohol mass 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 emission speaker, B is the magnetic flux
density in the magnetic gap, and C 9 is the total length of the conductor of the voice coil. Become.
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-radiating speaker, it
becomes mainly the resistance RV of the voice coil, including a small amount of inductance There
is. Next, the operation of the acoustic device having the configuration of FIGS. 1 and 2 will be
described. When a drive signal having a negative impedance drive function is supplied to the
speaker unit 3 from the drive circuit 30, the unit 3 electromechanically converts it to drive the
diaphragm 2 back and forth (left and right in FIG. 2). The diaphragm 2 mechanically acoustically
converts this reciprocating motion. 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 response to the drive signal input to the drive
circuit 30 in a faithful manner, and is independent of the Helmholtz resonator composed of the
resonance boat 8 and the cabinet 1 described above. Drive energy. At this time, the front side
(right side in FIG. 2) of the diaphragm 2 forms a direct radiation portion for radiating the sound
directly to the outside, and the rear side (left side in FIG. 2) of the diaphragm 2 ) Comprises a
resonator drive unit for driving a Helmholtz resonator consisting of a cabinet 1 and a resonance
boat 8. Therefore, the sound is directly emitted from the diaphragm 2 as shown by the arrow a in
the figure, and the air in the cabinet 1 is resonated, and as shown by the arrow in the figure, the
resonance radiation portion Sound of sufficient sound pressure is resonantly emitted from the
opening of the boat 8). Then, by adjusting the air equivalent mass in the resonance boat 8 in the
Hermholtz resonator, this resonance frequency f. By setting P to a Helmholtz resonance
frequency f op = f oc / in the system of FIG. 2 lower than f T and setting the Q value to an
appropriate level by adjusting the equivalent resistance of the resonance boat 8, appropriate
from the above opening Under the condition that the sound pressure of the level is obtained, the
frequency characteristic of the sound pressure as shown by the solid line in FIG. 4 can be
obtained, for example, by appropriately increasing or decreasing the manual signal level.
In FIG. 4, a two-dotted line indicates the frequency characteristic and impedance characteristic of
the closed speaker system, and a broken line indicates frequency characteristic and impedance
characteristic of the bass reflex speaker system. The operation in the case of negative impedance
driving of a speaker system using a Helmholtz resonator will be described below. FIG. 5 is an
electrical equivalent circuit when ZV−20 = o in FIG. 3, that is, when the internal impedance (nonmotional impedance) of the speaker unit 3 is equivalently completely nullified. Here, the
coefficient attached to the value of each element is omitted. The following is apparent from this
equivalent circuit. First, both ends of the parallel resonant circuit Z1 based on the equivalent
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motional impedance of the speaker unit 3 are shorted with zero impedance in an alternating
manner. Therefore, the parallel resonant circuit Z1 has a Q value of O and is substantially no
longer a resonant circuit. That is, in the speaker unit 3, the concept of the lowest resonance
frequency which has been provided in the state where the speaker unit 3 is simply attached to
the Helmholtz resonator is no longer present. Thereafter, the lowest resonance frequency f of the
speaker unit 3. In the case of a considerable amount, the above concept which has been
substantially nullified is only provisionally called. Thus, as a result of the unit resonance system
(parallel resonance circuit) Z + not being substantially a resonance circuit, the resonance system
in this acoustic device is only one Helmholtz resonance system (series resonance circuit) Z2.
Moreover, as a result of the vibration system being substantially non-resonant, the speaker unit 3
responds linearly in real time to the drive signal human power in real time, and does not make a
transient response at all, faithfully The mechanical conversion is performed to displace the
diaphragm 2. That is, it is a complete braking state (a so-called speaker dead state). The output
sound pressure frequency characteristic in the vicinity of the lowest resonance frequency fo
equivalent value of this speaker in this state is 6 d B / oc t. On the other hand, the characteristic
of the normal voltage drive state is 12 dB / o c t. On the other hand, the series resonance circuit
Z according to the equivalent motional impedance of the Helmholtz resonator is the drive signal
source E. Since the parallel resonant circuit z1 is connected with zero impedance, there is no
mutual dependency with the parallel resonant circuit z1, and the parallel resonant circuit Z1 and
the series resonant circuit Z2 independently coexist independently.
Therefore, the volume of the cabinet 1 (inverse to Sc) and the shape and size of the resonant boat
8 (proportional to mp) do not affect the direct radiation characteristics of the loudspeaker unit 3
and also the resonant frequency and Q of the Helmholtz resonator The value is also not
influenced 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 resonant circuit Z2 is r (+ rp
only, and these are usually small enough, the Q value of this series resonant circuit Z2, that is,
the Helmholtz resonator should be set sufficiently high. it can. From another point of view, since
the unit vibration system is effectively not a resonant system, it is displaced according to the
drive signal human power, and is not substantially affected by the external force, particularly the
atmospheric reaction by the equivalent stiffness Sc of the cabinet. . Therefore, the diaphragm 2 of
the speaker unit 3 is an isometric wall as seen from the cabinet side, and the presence of the
speaker unit 3 when viewed from the Helmholtz resonator is nullified. Therefore, the resonance
frequency and Q value as the Helmholtz resonator do not depend on the non-motional impedance
of the speaker unit 3, and this resonance frequency is set to a frequency such that the resonance
Q value becomes very small in the normal drive system. Also in the case where it does, the Q
value can be maintained at a sufficiently large value. In addition, the Helmholtz resonance system
is a virtual speaker that emits sound 1 completely independently of the unit vibration system.
And although this virtual speaker is realized with a small aperture equivalent to the boat
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diameter, it is equivalent to an extremely large aperture as a real loudspeaker from the viewpoint
of 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 a normal power amplifier, in the
conventional system, as is well known, a plurality of resonance systems of unit vibration system
Z1 and Hermholtz resonance system Z2 And the resonant frequency and Q value of each
resonant system were closely dependent on each other. For example, if the boat is lengthened or
narrowed (mp is increased) to lower the resonance frequency of the Helmholtz resonance system
Z2, the Q value becomes high in the unit vibration system Z, and becomes low in the Helmholtz
resonance system Z2, If the volume of the cabinet is reduced (SC becomes large), even if the boat
is lengthened or narrowed to keep the resonance frequency of Helmholtz single-port Z1 constant,
the unit vibration system Z, the Q value and the The resonance frequency is increased, and the Q
value is further lowered in the Helmholtz resonance system Z2.
That is, since 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 boat, a high level design technique is required to match them, and the output It is generally
impossible to miniaturize the cabinet (system) without compromising the sound pressure
frequency characteristics, particularly the low frequency characteristics, and easily expand the
sound reproduction band of the existing system without compromising the characteristics of the
sound quality and the like. It was thought. Further, the relationship between the frequency in the
band lower than the resonance frequency for the Hermholtz resonance system Z2 and the
resonance acoustic radiation ability is about 12 d B / o c with respect to the reduction of the
frequency in terms of the sound pressure level. If the resonance frequency is set extremely low
with respect to the basic concept of the bass reflex type speaker system, the correction due to the
increase or decrease of the manual signal level becomes extremely difficult. As described above,
since the drive system of this embodiment drives the speaker system utilizing Helmholtz
resonance with negative impedance, the characteristics, dimensions, etc. of the unit vibration
system and Hermholtz resonance system of the system can be set independently. And, 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 10 at), A feature is obtained that the frequency characteristics can be
corrected by increasing or decreasing the input signal level, for example, by changing the level of
normal sound quality adjustment. Therefore, the cabinet can be miniaturized to reduce the
speaker system without deteriorating the frequency characteristics and sound quality. It can be
configured to be smaller, and the existing speaker system can be more compact than the
conventional constant voltage drive. Improve the quality, or sound reproducing band can
particularly be driven easily expand the bass side. In the above description, only the case of ZV20 = Q has been described, but the present invention also includes the case of ZvZo> O if -Zo <0.
In this case, the characteristic values and the like of the unit vibration system and the Helmholtz
resonance system become values between the case of Zv Zo “O” and the case of the
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conventional constant voltage drive system according to the value of the impedance ZV-20.
Therefore, using this property positively, for example, adjustment of Q value of Helmholtz
resonance system is performed instead of adjusting the boat diameter or inserting mechanical Q
damper such as glass wool or felt in the cabinet. , Negative impedance -Z.
It can be done by adjusting the Also, in this case, it was extremely difficult for a general user to
set the output impedance properly and increase / decrease the input signal level with a variable
resistor, a changeover switch, etc., but as shown in FIG. The transfer characteristic of the
feedback circuit 63 is set or changed by setting or replacing the cartridge, and the negative
impedance value of -2 ° etc. is set to the system to be driven, so that the negative impedance
value -Zo is appropriate. Setting to the value has become extremely easy. The closed speaker
system is obtained by removing the resonance boat of the above-mentioned speaker system with
a resonance boat. Therefore, in the equivalent circuit of FIGS. 3 and 5, the equivalent mass mp of
the resonance boat (1), That is, it can be grasped that the capacitor mP / A2 is shorted. That is,
also in the closed speaker system, the minimum resonance frequency of the speaker unit is
driven by the power amplifier including the negative impedance in the output impedance, and by
increasing or decreasing the manual signal level of this power amplifier. f. It is possible to realize
relatively high quality reproduction to near the equivalent value. FIG. 6 shows the basic
configuration of a negative impedance generating circuit for driving a vibrator in negative
impedance. The circuit shown in the figure gives the output of the amplifier 61 of gain A to the
load ZL by the speaker 3. Then, the current IL flowing to the load ZL is detected, and is positively
fed back to the amplifier circuit 61 via the feedback circuit 63 of the transmission gain β. In this
way, the output impedance Z of the circuit. Is obtained as Zo = Z, (1-A.beta.) (4). From this
equation (4), if Aβ> 1, then Z. Becomes an open stable negative impedance. Here,% ZS is an
impedance of a sensor that detects a 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 Zs. For example, when current ■ is detected by the voltage across impedance
Zs, if impedance ZS is resistance R3, the negative impedance component will be a negative
resistance component, and if it is inductance Ls, it will be a negative inductance component, and
capacitance C5 If it is, it becomes a negative capacitance. Further, by using an integrator for 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 a negative resistance component,
and furthermore, a differentiator for the feedback circuit 63 The negative impedance component
becomes a negative resistance component even if the voltage across the capacitance C9 as the
impedance z5 is differentiated and detected.
Tit? As the a detection sensor, it is also possible to use a current probe such as C, T or a Hall
element other than these impedance elements Rs, Ls, Cs, etc. A specific example corresponding to
such a circuit is shown, for example, in Japanese Patent Publication No. 59-51771. It is also
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possible to perform current detection on the non-grounded side of the speaker 3. An example of
such a circuit is shown, for example, in Japanese Patent Publication No. 54-33704. FIG. 7 is an
example of BTL connection, but it is easy to apply to the circuit of 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 the 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 (.OMEGA.). Further, in FIG. 8, a portion 32 surrounded by a
dotted line corresponds to the in-cartridge circuit 32 of FIG. [Modification of the embodiment]
The present invention is not limited to the above-described embodiment, and can be
appropriately modified and implemented. For example, although the example in which the entire
equalizer circuit 34 and feedback circuit 63 are separated from the drive device body 10 and
stored in the cartridge 15 as the control information storage body has been described above, 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 it contains a portion sufficient to change or set the
feedback characteristic of. Further, although the example in which the analog circuit information
is stored as the control information has been described above, the control information may be
digital data. In this case, for example, a digital filter is used as the equalizer circuit 34 and the
feedback circuit 63, and an A / D converter for digitizing the output of the detection element Zs
is provided between the feedback circuit 63 and the current detection element Z3. Further, as the
control information medium, a ROM, a magnetic or punch card or the like can be used instead of
the analog circuit in the above embodiment. When a card is used as the medium, a card reader is
provided instead of the connector 12.16, and a data storage RAM etc. is provided inside. In
addition, as shown in FIG. 9, the cartridges 15A, 15B,... Correspond to one speaker system, for
example, 21A, and plural types 15A-1, 15A-2,. It is possible to prepare and set the characteristics
such as the output impedance of the drive device in accordance with the type of the speaker
system and the music to be generated, such as jazz, classical music,.
In FIG. 9, (a) shows the frequency characteristic of the sound pressure output in the constant
voltage driving state, and (b) shows the frequency characteristic of the sound pressure output
when the characteristic value of the negative impedance driving is set for each music. Show. The
drive circuit may be any one as long as it drives the vibrator of the electroacoustic transducer so
as to cancel the reaction from the surroundings, and is, for example, a so-called MFB circuit as
disclosed in Japanese Patent Publication No. 58-31156. It is also good. Furthermore, by giving
frequency characteristics to the output impedance, it is possible to improve the degree of
freedom in setting Qoc 'and Qop.
[0002]
Brief description of the drawings
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[0003]
FIG. 1 is a schematic external view showing a basic configuration of a drive device according to
an embodiment of the present invention, FIG. 2 is an explanatory view of a circuit configuration
of the drive device of FIG. 1, and FIG. 3 is FIG. 2 and FIG. 4 are the sound pressure frequency
characteristics of the sound emitted from the acoustic device of FIGS. 1 and 2, and FIG. 5 is the
diagram of FIG. 6 and 7 are basic circuit diagrams of a circuit generating negative impedance,
and FIG. 8 is a specific circuit diagram of negative resistance driving, and FIG. 9 (a) and 9 (b) are
explanatory views showing a modification of the drive device of FIG. 1, FIG. 10 is a crosssectional view showing the configuration of a conventional closed speaker system, and FIG. 11 is
a conventional bass reflex 12 is a cross-sectional view showing the configuration of the speaker
system of FIG. 10 and FIG. Explanatory drawing of pressure characteristics, FIG. 13 is
explanatory drawing of a circuit and frequency characteristic in the case of carrying out constant
voltage drive of the speaker unit attached to the small cabinet by the signal which boosted the
bass, and FIG. 14 concerns the prior application. It is a basic composition figure of a negative
impedance generating circuit.
DESCRIPTION OF SYMBOLS 1; Cabinet 2: 2: Shooting plate 3: Speaker unit 8: Resonant boat 10:
Drive device body 12: 16: Connector 15A, 15B ... Cartridge: 21A, 21B, ... · Nisveaker system, 30:
drive circuit, 31: circuit in the main body, 32: circuit in the cartridge, 34; equalizer circuit, 60:
negative impedance generating circuit.
08-05-2019
11
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