EP0435304B1 - Appareil acoustique et appareil de commande associé - Google Patents

Appareil acoustique et appareil de commande associé Download PDF

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Publication number
EP0435304B1
EP0435304B1 EP19900125621 EP90125621A EP0435304B1 EP 0435304 B1 EP0435304 B1 EP 0435304B1 EP 19900125621 EP19900125621 EP 19900125621 EP 90125621 A EP90125621 A EP 90125621A EP 0435304 B1 EP0435304 B1 EP 0435304B1
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EP
European Patent Office
Prior art keywords
power amplifier
circuit
loudspeaker
driving
loudspeaker unit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19900125621
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German (de)
English (en)
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EP0435304A3 (en
EP0435304A2 (fr
Inventor
Kenji C/O Yamaha Corporation Yokoyama
Masao C/O Yamaha Corporation Noro
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Yamaha Corp
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Yamaha Corp
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Publication date
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Publication of EP0435304A2 publication Critical patent/EP0435304A2/fr
Publication of EP0435304A3 publication Critical patent/EP0435304A3/en
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Publication of EP0435304B1 publication Critical patent/EP0435304B1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits

Definitions

  • the present invention relates to an acoustic apparatus which is connected to a general-purpose or usual power amplifier for normally driving a loudspeaker and improve electro-acoustic reproduction (transduction) characteristics of an loudspeaker constituting the acoustic apparatus, and a driving apparatus for driving the loudspeaker to improve its electro-acoustic reproduction characteristics in cooperation with the general-purpose power amplifier.
  • a conventional power amplifier for driving a loudspeaker normally has a substantially zero output impedance, and constant-voltage drives the loudspeaker.
  • Japanese Patent Application Laid-Open Gazette No. Sho 58-29295 discloses a technique that a loudspeaker is connected in series with a negative resistance circuit having a negative resistance at a predetermined frequency or less, and the series circuit of the loudspeaker and the negative resistance is driven by a general-purpose amplifier to improve bass tone range characteristics of the loudspeaker.
  • the negative resistance circuit uniquely disclosed in the embodiment of Japanese Patent Application Laid-Open Gazette No. Sho 58-29295 is a transistor class-A single amplifier which has a resistor as a load.
  • Such a transistor class-A single amplifier is not used for supplying power to a low-impedance load such as a loudspeaker in terms of voltage utilization efficiency, power loss, cost, and the like except for a case wherein it is used for a very small power such as an earphone or a headphone, or a very special case like in a hobby use. More specifically, this transistor class-A single amplifier does not belong to a category of power amplifiers for driving a loudspeaker in a general idea.
  • an impedance Z which is a detection resistor corresponding to a detection resistor Rs for speaker current detection according to the present invention, is connected in series with the loudspeaker unit through a transistor and, an emitter resistor is connected at one end to a point where the emitter of the transistor and loudspeaker unit 2 are connected each other and is also connected at its other end to a grounding point.
  • this negative resistance circuit is not constituted by a push-pull circuit and; among A class amplifiers, the negative resistance circuit is restricted in its applicability, it cannot simply be replaced with a power amplifier circuit which precisely detects the speaker current thereby to enable it to output the optimal negative resistance and is generally suitable for driving the speaker.
  • the EP-A 0 293 806 discloses a dynamic loudspeaker driving apparatus, which comprises an amplifier to one input of which the motional voltage of the loudspeaker is negatively feeded back.
  • This loudspeaker driving apparatus corresponds to the apparatus which are disclosed in the above-mentioned EP-A 0 322 686, 0 322 679 and 0 332 053 since, also the so-called motional feedback driving (MFB-driving) is applied.
  • MFB-driving motional feedback driving
  • the loudspeaker driving apparatus disclosed in the EP-A-0 293 806 needs a special power amplifier corresponding to the loudspeaker to be used. Therefore, also in this case the power amplifier cannot be used, if the user who possesses and regularly uses a general-purpose power amplifier wants to constitute the MFB-system.
  • an apparatus for driving a loudspeaker unit in cooperation with an external power amplifier for constant-voltage-driving a loudspeaker is provided as set forth in claim 1.
  • Preferred embodiments are disclosed in the dependent claims.
  • a dynamic loudspeaker driving apparatus in which, in addition to the conventional external power amplifier, an additional power amplifier unit is provided for driving a loudspeaker in cooperation with said conventional general-purpose power amplifier to improve the electro-acoustic reproduction characteristics of the loudspeaker, and for generating an electric energy corresponding to an increase in energy from that in a normal or conventional driving operation during driving operation for improving the characteristics.
  • a normal driving energy as another energy is supplied from the general-purpose power amplifier.
  • the normal driving energy is supplied from the general-purpose power amplifier as a conventional power amplifier
  • a user who regularly uses the general-purpose power amplifier can utilize it to realize negative-impedance driving or MFB driving, thereby improving electro-acoustic reproduction characteristics of his or her or a commercially available loudspeaker.
  • a compact acoustic apparatus (loudspeaker system) which can automatically attain negative-impedance driving or MFB driving when it is driven by a general-purpose power amplifier, and has good electro-acoustic reproduction characteristics can be realized.
  • the driving apparatus of the present invention since an electric energy corresponding to an increase in energy caused by the negative-impedance driving or MFB driving is supplied from the second power amplifier, an output from the general-purpose power amplifier which cooperates with the second power amplifier can be efficiently utilized. Furthermore, since the second power amplifier need only supply an electric energy corresponding to an increase in energy caused by the negative-impedance driving or MFB driving, it can be rendered compact and inexpensive as compared to a conventional driving apparatus exclusively used for negative-impedance driving or MFB driving.
  • Fig. 1 shows an arrangement of an acoustic apparatus according to an embodiment of the present invention.
  • This acoustic apparatus performs negative-impedance driving to improve loudspeaker characteristics.
  • a loudspeaker unit 2 and an amplifier unit 3 serving as a negative-impedance driving apparatus as the characteristics feature of the present invention are disposed in a cabinet 1 having a resonance duct port 11.
  • the apparatus also has a pair of external input terminals P1 and P2 for connecting this acoustic apparatus to output terminals of a power amplifier 5 as a general-purpose power amplifier.
  • the amplifier unit 3 comprises a power amplifier circuit 31, a positive feedback circuit 32, and a transfer function control circuit 33.
  • the positive feedback circuit 32 comprises a feedback amplifier A1 given with a predetermined transfer function ⁇ by an impedance element Zs for detecting a loudspeaker current, impedance elements Za and Zb, and the like.
  • the impedance value of the impedance element Zs has a negligible magnitude as compared to that of the loudspeaker unit 2.
  • one external input terminal P1 is connected to one input terminal P3 of the loudspeaker unit 2 via the impedance element Zs for detecting the loudspeaker current
  • the other input terminal P4 of the loudspeaker unit 2 is connected to an operation reference potential point of the amplifier unit 3. Furthermore, a detection output obtained by detecting a current flowing through the loudspeaker unit 2 by the impedance element Zs is positively fed back to the input of the power amplifier circuit 31 via the feedback amplifier A1.
  • an input signal supplied to the external input terminal P1 is also supplied to the input of the power amplifier circuit 31 via the transfer function control circuit 33 having a predetermined transfer function.
  • the amplifier unit 3 negative-impedance drives the loudspeaker unit 2 in cooperation with the power amplifier 5.
  • This negative-impedance driving is performed in the same manner as in the acoustic apparatus disclosed in European Patent Application Publication No. 0 322 686. Accordingly, in the circuit shown in Fig. 1, for example, in a low frequency range, such negative resistance drive that is disclosed in European Patent Application Publication No. 322,686 is performed, whereby the speaker unit 2 is damped and driven extremely strongly and the reproduction characteristics, especially low frequency range characteristics thereof, is improved or whereby a cabinet can be made small in size, or a speaker system as a whole can be made small in size without damaging the reproduction characteristics.
  • Fig. 2 shows the second embodiment of the present invention.
  • a dynamic loudspeaker is used as the loudspeaker unit 2 to express the overall circuit in more detail as compared to the circuit shown in Fig. 1, and loudspeaker current detection operation is performed at a ground side.
  • An internal impedance of the dynamic loudspeaker mainly consists of a resistance (Rv) of a voice coil, and slightly includes an inductance component.
  • a resistor Rs is used as the loudspeaker current detection impedance element Zs so that the output impedance Zo expressed by equation (2) serves as a negative resistance (-Rv) for canceling the internal resistance Rv.
  • resistors are also used as impedance elements for determining the positive feedback gain ⁇ and the amplifier gain A.
  • an amplifier A3 constituting the transfer function control circuit 33 also serves as a DC servo amplifier. More specifically, a signal supplied to the external input terminal P1 is non-inverting amplified by the amplifier A3 of the transfer function circuit 33, and the amplified signal is inputted to the non-inverting input terminal of an amplifier (internal power amplifier) A2 constituting the power amplifier circuit 31. In addition, by utilizing the inverted input terminal of the amplifier A3, a DC fluctuation of the internal power amplifier A2 is compensated for by negative feedback circuit (amplifier A2 and a capacitor).
  • the acoustic apparatus shown in Fig. 2 generates a negative resistance (-Rv) for canceling the internal impedance Rv of the loudspeaker unit 2 independently of the loudspeaker unit 2.
  • the loudspeaker unit 2 is equivalent to a circuit in which a motional impedance Z M is directly connected to voltage sources 5 and 31 without going through an impedance such as the internal impedance Rv or the like. Since the voltage sources have an internal impedance of zero respectively, the motional impedance Z M of the loudspeaker unit 2 is short-circuited at its two ends so that its resonance frequency Q becomes zero.
  • the loudspeaker is set in a perfect dead state, and is very strongly driven and damped.
  • the transfer function T(s) of the transfer function control circuit 33 is appropriately set so that the output voltage of the power amplifier circuit 31 for generating a negative resistance is decreased, thus power supply from the power amplifier 5 can be increased, and desired frequency compensation in a negative-impedance driving mode can be performed.
  • This acoustic apparatus has a merit in that a conventional general-purpose power amplifier can be directly used, and characteristics unique to the power amplifier can be directly used, and characteristics unique to the power amplifier can be sufficiently reflected when the loudspeaker is driven.
  • a negative impedance (-Rv) is connected in series with a loudspeaker 1".
  • an equalizer circuit such as the transfer function control circuit 33 is required to adjust output characteristics of the loudspeaker.
  • the equalizer circuit may be connected in series with the loudspeaker unit 2", as indicated by Z EQ in Fig. 3C. In this case, the effect of the negative resistance -Rv is reduced, and the damping force of the motional impedance Z M of the loudspeaker unit 2 is decreased. Furthermore, as shown in Fig.
  • the negative resistance (-Rv) circuit is constituted by a transistor class-A single amplifier including an emitter resistor as a resistance load, this transistor equivalently drives a parallel circuit of the loudspeaker 2 and the emitter resistor. Therefore, when this emitter resistance is set to be sufficiently smaller than the impedance of the loudspeaker unit 2, power consumption of the negative resistance transistor is increased beyond a practical level. On the other hand, when the emitter resistance is increased, since the emitter resistance is connected in series with the loudspeaker unit 2 with respect to the amplifier 5, the output from the amplifier 5 is consumed and decreased by the emitter resistance. In any case, the negative resistance circuit disclosed in Japanese Patent Appln. Laid-Open Gasette No. Sho 58-29295 is not practical in terms of cooperation with a general-purpose amplifier.
  • the apparatus of the present invention has not such defects as those in the conventional apparatus disclosed in Japanese Pat. Appln. Laid-Open Gazette No. Sho 58-29295 since the former has an element (resistor) for detecting a current flowing through the speaker, between the loudspeaker unit and the negative resistance circuit.
  • the conventional apparatus wherein an element for detecting a current through a speaker is arranged between a power source B+ and a negative resistance circuit, cannot constitute a push-pull circuit (since + and - must be taken into consideration).
  • Fig. 4 shows the third embodiment of the present invention.
  • an output from the transfer control function control circuit 33 is shifted by a voltage across the loudspeaker current detection resistor Rs, and is amplified by the amplifier circuit 31 with reference to a voltage at the right terminal side (Fig. 4) of the resistor Rs.
  • Fig. 5 is a detailed circuit diagram of the acoustic apparatus shown in Fig. 4.
  • the transfer function control circuit 33 is constituted by only passive elements.
  • Fig. 6 shows the fourth embodiment of the present invention.
  • the acoustic apparatus shown in Fig. 6 drives a woofer WF of a two-way loudspeaker system by a negative-impedance circuit as the characteristic feature of the present invention.
  • a power supply 7 generates DC power supply voltages +B 1 and -B 1 for the power amplifier A2 and DC power supply voltages +B 2 and -B 2 for the current detection amplifier A1, the amplifier A3 in the transfer function circuit 33, and a protection circuit 8 on the basis of an AC power supply, e.g., a commercial power supply of 100 V.
  • the protection circuit 8 is used to prevent destruction or degradation of the circuits and the loudspeaker units caused by an overload, transient, or abnormal operation.
  • the protection circuit 8 has a DC protection function of turning off a relay contact ry1 when a DC current exceeding a predetermined value flows through the loudspeaker unit, an overcurrent protection function of turning off the relay contact ry1 when an overcurrent flows through the loudspeaker unit, a heat radiation plate temperature protection function of turning off the relay contact ry1 when the temperature of a heat radiation plate exceeds a predetermined value, and a power-on muting function of turning on the relay contact ry1 after the lapse of a predetermined delay time when a power switch is turned on.
  • This apparatus also has protection means, e.g., for a primary fuse, a temperature fuse in a transformer, and the like (not shown).
  • Fig. 7 is a detailed circuit diagram of the acoustic apparatus shown in Fig. 6.
  • an IC (STK4040V) 30 is a hybrid IC formed by integrating the amplifiers A1, A2, and A3, and some of their peripheral circuits shown in Fig. 6.
  • a DC power supply 7 comprises a power supply transformer 71 having a central tap type secondary winding voltage, and a full-wave rectification circuit 72, and generates two DC voltages +B 1 and -B 1 . These voltages are directly supplied to the amplifier A2 in the IC 30, and are also supplied to a circuit including the amplifiers A1 and A3, and the like as voltages +B 2 and -B 2 via a decoupling circuit 73.
  • the speaker current detection resistor Rs has a resistance 0.2 ⁇ .
  • a resistor R 81 and a capacitor C 81 allow only a DC voltage component of a signal appearing at the external input terminal P1 to pass therethrough.
  • this DC voltage is equal to or higher than +0.6 V
  • a transistor Q 81 is turned on, and transistors Q 82 and Q 83 are turned off.
  • a relay solenoid RY1 is deenergized, and the relay contact ry1 is turned off.
  • the DC voltage component is equal to or lower than -0.6 V
  • a base current of the transistor Q 82 is bypassed through diodes D 81 and D 82 , and the transistors Q 82 and Q 83 are turned off to deenergize the relay solenoid RY1.
  • the protection circuit 8 realizes the DC protection function with these operations.
  • the transistor Q 81 When the temperature of the heat radiation plate exceeds a predetermined value, a voltage-divided value of the resistor R 82 and the positive characteristic thermistor PTH exceeds 1.2 V. Thus, the transistor Q 81 is supplied with the base current through a diode D 84 , and is turned on. The transistors Q 82 and Q 83 are turned off to deenergize the relay solenoid RY1, and the relay contact ry1 is turned off. That is, the heat radiation plate temperature protection function can be realized.
  • the power switch 9 When the power switch 9 is turned on, a capacitor C 82 is charged through a resistor R 83 , and the transistors Q 82 and Q 83 are kept off until the terminal voltage across the capacitor C 82 exceed 0.6 V. Therefore, during this interval, the relay contact ry1 is kept off, and a signal to the woofer WF. and a circuit corresponding to the amplifier unit 3 is cut off. That is, the power-on muting function can be realized.
  • a primary fuse FS is arranged.
  • a temperature fuse (not shown) is also arranged in the power supply transformer 71.
  • Fig. 8 shows the fifth embodiment of the present invention.
  • This acoustic apparatus can perform the same MFB (motional feedback) driving as in the acoustic apparatus disclosed in European Patent Application Publication No. 0 332 053 by utilizing the general-purpose power amplifier 5.
  • a loudspeaker unit 2 having a vibration sensor 21, and an amplifier unit 3 serving as an MFB driving apparatus as the characteristic feature of the embodiment are arranged in a cabinet 1 having a resonance duct port 11.
  • this apparatus also has a pair of external input terminals P1 and P2 for connecting this acoustic apparatus to the output terminals of the power amplifier 5 as the general-purpose power amplifier.
  • one external input terminal P1 is connected to one input terminal P3 of the loudspeaker unit 2, and the other input terminal P4 of the loudspeaker unit 2 is connected to an operation reference potential point of the amplifier unit 3.
  • a detection output of a vibration state of the loudspeaker unit 2 by the vibration sensor 21 is negatively fed back to the input of a power amplifier circuit 31 of the amplifier unit 3, and a signal supplied to the external input terminal P1 is supplied to the input of the power amplifier circuit 31 via a transfer function control circuit 33 having a predetermined transfer function.
  • the vibration sensor 21 detects a vibration state of a diaphragm 22 of the loudspeaker unit 2 by any method, and comprises, e.g., a velocity sensor, a displacement sensor, acceleration sensor, or the like. Note that in place of the vibration sensor 21, a vibration state may be detected using a bridge circuit, as described in European Patent Application Publication No. 0 332 053.
  • the amplifier unit 3 comprises the power amplifier circuit 31, a negative feedback circuit 32', and the transfer function control circuit 33.
  • the negative feedback circuit 32' amplifies the detection output of the vibration sensor 21 or the vibration state detection bridge circuit with a predetermined transfer function ⁇ , and inputs the amplified output to the inverting input terminal of the power amplifier circuit 31.
  • the amplifier unit 3 cooperates with the general-purpose power amplifier 5, and the same MFB driving as in the acoustic apparatus disclosed in European Patent Application Publication No. 0 332 053 is performed as a whole.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Amplifiers (AREA)
  • Circuit For Audible Band Transducer (AREA)

Claims (13)

  1. Appareil acoustique pour piloter un module de haut-parleur (2) ayant deux bornes d'entrée (P3, P4) en coopération avec un amplificateur de puissance externe ayant deux bornes de sortie (P1, P2) qui est adapté à piloter en tension constante un haut-parleur, comprenant :
       un module amplificateur de puissance (3) pour produire une énergie électrique correspondant à une augmentation d'énergie par rapport à l'énergie d'un état de pilotage à tension constante, comprenant un circuit d'amplificateur de puissance (31) pour recevoir un signal à partir de la première borne de sortie (P1) de l'amplificateur de puissance externe (5) par l'intermédiaire d'un circuit à fonction de transfert (33) et pour utiliser l'autre borne de sortie (P2) de l'amplificateur de puissance externe en tant que point de potentiel de référence de fonctionnement, amplifier le signal reçu par une fonction de transfert prédéterminée, et piloter une première borne d'entrée (P4) du module de haut-parleur (2), l'appareil comprenant en outre un circuit de connexion pour connecter la première borne de sortie (P1) de l'amplificateur de puissance externe à l'autre borne d'entrée (P3) du module de haut-parleur (2).
  2. Appareil selon la revendication 1, caractérisé en ce que l'opération de pilotage à amélioration de caractéristiques est une opération de pilotage à impédance négative.
  3. Appareil selon la revendication 1, caractérisé en ce que l'opération de pilotage à amélioration de caractéristiques est une opération de pilotage à réaction de mouvement.
  4. Appareil selon l'une quelconque des revendications précédentes, caractérisé par un circuit de réaction, (32, 32') pour détecter un état de pilotage ou de fonctionnement du module de haut-parleur (2) et renvoyer une sortie de détection à un côté entrée du circuit d'amplificateur de puissance (31).
  5. Appareil selon la revendication 4, caractérisé en ce que le circuit de réaction (32) détecte un courant circulant dans le module de haut-parleur (2).
  6. Appareil selon la revendication 4 ou 5, caractérisé en ce que le circuit de réaction (32) renvoie positivement le courant détecté à partir du module de haut-parleur (2) et pilote en impédance négative en coopération avec le circuit d'amplificateur de puissance (31).
  7. Appareil selon l'une quelconque des revendications précédentes, caractérisé en ce que le module de haut-parleur (2) comprend un corps vibrant et un moyen pour détecter un état de vibration du corps vibrant.
  8. Appareil selon la revendication 4 ou 7, caractérisé en ce que le circuit de réaction (32') détecte un état de vibration du module de haut-parleur (2), renvoie négativement un signal de détection, et pilote à réaction de mouvement en coopération avec le circuit d'amplificateur de puissance (31).
  9. Appareil selon l'une quelconque des revendications 4, 7 ou 8, caractérisé par un circuit de réaction négative (32') pour renvoyer négativement une sortie de détection de l'état de vibration du corps vibrant vers un côté entrée du circuit d'amplificateur de puissance (31).
  10. Appareil selon l'une quelconque des revendications précédentes, caractérisé par une enceinte (1) pour contenir le module de haut-parleur (2) et le module d'amplificateur de puissance (3).
  11. Appareil selon la revendication 10, caractérisé en ce que le module d'amplificateur de puissance (3) comprend un circuit d'amplificateur de puissance (31), le circuit de réaction positif (32) et/ou le circuit à fonction de transfert (33).
  12. Appareil selon la revendication 10, caractérisé en ce que l'enceinte (1) a une structure de résonateur.
  13. Appareil selon la revendication 10 ou 11, caractérisé en ce que l'enceinte (1) comporte un accès de conduit de résonance (11).
EP19900125621 1989-12-26 1990-12-27 Appareil acoustique et appareil de commande associé Expired - Lifetime EP0435304B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP33521089A JP3035943B2 (ja) 1989-12-26 1989-12-26 音響装置およびこのような音響装置を構成するための駆動装置
JP335210/89 1989-12-26

Publications (3)

Publication Number Publication Date
EP0435304A2 EP0435304A2 (fr) 1991-07-03
EP0435304A3 EP0435304A3 (en) 1991-10-23
EP0435304B1 true EP0435304B1 (fr) 1998-07-29

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Application Number Title Priority Date Filing Date
EP19900125621 Expired - Lifetime EP0435304B1 (fr) 1989-12-26 1990-12-27 Appareil acoustique et appareil de commande associé

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EP (1) EP0435304B1 (fr)
JP (1) JP3035943B2 (fr)
DE (1) DE69032523T2 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004021546A1 (de) * 2004-05-03 2005-12-08 Avantgarde Acoustic Lautsprechersysteme Gmbh Hornlautsprecher

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4887968B2 (ja) * 2006-08-09 2012-02-29 ヤマハ株式会社 音声会議装置
US8401207B2 (en) * 2009-03-31 2013-03-19 Harman International Industries, Incorporated Motional feedback system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4550430A (en) * 1981-02-20 1985-10-29 Meyers Stanley T Sound reproducing system utilizing motional feedback and an improved integrated magnetic structure
US4638258A (en) * 1982-02-26 1987-01-20 Barcus-Berry Electronics, Inc. Reference load amplifier correction system
US5031221A (en) * 1987-06-02 1991-07-09 Yamaha Corporation Dynamic loudspeaker driving apparatus
JPH0728473B2 (ja) * 1988-05-06 1995-03-29 ヤマハ株式会社 インピーダンス補償回路

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102004021546A1 (de) * 2004-05-03 2005-12-08 Avantgarde Acoustic Lautsprechersysteme Gmbh Hornlautsprecher

Also Published As

Publication number Publication date
EP0435304A3 (en) 1991-10-23
DE69032523T2 (de) 1999-04-08
EP0435304A2 (fr) 1991-07-03
JP3035943B2 (ja) 2000-04-24
JPH03196798A (ja) 1991-08-28
DE69032523D1 (de) 1998-09-03

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