EP0171065A2 - Arrangement for the acoustic feedback of loudspeakers - Google Patents

Arrangement for the acoustic feedback of loudspeakers Download PDF

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Publication number
EP0171065A2
EP0171065A2 EP85109881A EP85109881A EP0171065A2 EP 0171065 A2 EP0171065 A2 EP 0171065A2 EP 85109881 A EP85109881 A EP 85109881A EP 85109881 A EP85109881 A EP 85109881A EP 0171065 A2 EP0171065 A2 EP 0171065A2
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Prior art keywords
microphone
loudspeaker
arrangement according
membrane
attached
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EP85109881A
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German (de)
French (fr)
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EP0171065A3 (en
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Friedrich Müller
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Individual
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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 invention relates to an arrangement for acoustic negative feedback of loudspeakers with at least one microphone, which supplies a voltage proportional to the sound pressure generated by the loudspeaker, with a microphone amplifier, with a summing point, which adds the amplified microphone voltage in phase opposition to the control signal of the loudspeaker, with one downstream of the summing point PI controller and with a subsequent power amplifier to control the loudspeaker.
  • a negative feedback leads to an improvement in the frequency response, the distortion factor and the pulse fidelity of the loudspeaker, which leads to a lifelike reproduction.
  • a loudspeaker circuit with acoustic negative feedback in which the negative feedback signal is obtained with a microphone from the sound field in front of the loudspeaker, this signal is added in phase opposition to the control signal of the loudspeaker and the sum voltage is fed to the loudspeaker via an amplifier (German Offenlegungsschrift 31 37 747). .
  • the microphone is spaced in front of the speaker. Which are presented The resulting propagation time of the sound from the loudspeaker to the microphone has an effect in the control loop as a frequency shift, negative phase shift. Even at relatively low frequencies, this leads to inadequate stability of the control loop, which manifests itself in the tendency of the circuit to oscillate. Attempts are being made to counter this problem by specifically setting the frequency response of the open control loop.
  • a disadvantage of the known methods for acoustic negative feedback from loudspeakers is that the inevitable transit times of the sound from the loudspeaker to the microphone generally result in an inadequate stability of the control loop, which is difficult to control.
  • the constantly changing distance between the loudspeaker membrane and the microphone results in additional amplitude and intermodulation distortions. Since strong air currents occur in the area in front of the loudspeaker diaphragm, the microphone also picks up unwanted noise.
  • the present invention has for its object to propose an arrangement for acoustic negative feedback of speakers that does not have the disadvantages mentioned; in particular, the negative feedback circuit should be characterized by improved stability.
  • an arrangement for acoustic negative feedback of loudspeakers is assumed and is achieved in that the microphone is attached to the loudspeaker diaphragm.
  • the microphone thus moves with the loudspeaker membrane; the effective distance between the two is practically reduced to zero.
  • the propagation time of the sound between the loudspeaker membrane and the microphone is negligible, so that a negative effect on the stability behavior of the negative feedback circuit is excluded.
  • the arrangement according to the invention thus makes it possible for the first time to use the principle of acoustic negative feedback by means of a signal obtained from the sound field of the loudspeaker, without at the same time having to accept difficult control problems with regard to the stability of the control loop. Amplitude and intermodulation distortions are also excluded due to the unchangeable position of the microphone on the loudspeaker membrane. Since the microphone is no longer in the area of strong air currents, it also absorbs less noise.
  • the microphone is attached in an advantageous embodiment of the invention in the region of the edge of the loudspeaker diaphragm.
  • electret microphones are advantageously used for mounting on the loudspeaker membrane.
  • an electret microphone also acts as an accelerometer during a movement perpendicular to its microphone membrane
  • its membrane is expediently attached in the direction of movement of the loudspeaker membrane.
  • two identical microphones are advantageously arranged mechanically antiparallel, with their microphone voltages being added electrically. This largely compensates for structure-borne noise.
  • a stationary plate is arranged in front of the loudspeaker membrane in the area of the microphone.
  • this plate does not shade external noises generated by the loudspeaker, on the other hand it causes an increase in the sound pressure in the surface due to the sound reflections on its surface opposite the loudspeaker membrane Area of the microphone; this effectively improves the ratio between the interference signal and the useful signal of the microphone.
  • the stationary plate is expediently arranged essentially perpendicular to the direction of movement of the loudspeaker diaphragm.
  • the fixed plate covers about a quarter of the area of the loudspeaker diaphragm and the microphone is located approximately in the middle of this covered area. This dimensioning already achieves a significant improvement in the signal-to-noise ratio of the microphone without too much interference with the free sound radiation from the loudspeaker.
  • the plate works well with a minimum distance of around 1 cm between the plate and the moving speaker cone.
  • FIG. 1 The principle of acoustic negative feedback of a loudspeaker 1 is shown in FIG.
  • a microphone 2 which supplies a voltage proportional to the sound pressure.
  • this voltage is added in a summing point 4 in phase opposition to the control signal of the loudspeaker 1.
  • a PI controller 5 Downstream of the summing point is a PI controller 5, which is set in such a way that it increases the low frequencies, which contributes to the stability of the control loop.
  • a power amplifier 6 amplifies the control signal as far as is required to operate the loudspeaker 1.
  • the microphone 2 is attached directly to the front of the loudspeaker membrane 7.
  • An arrangement is shown here using a small electret microphone in the area of the edge 8 of the loudspeaker membrane 7, the membrane of which is attached to the loudspeaker membrane 7 in the direction of movement 9.
  • the attachment of the microphone 2 on the surface of the speaker diaphragm 7 is done in the simplest case by gluing; however, additional fasteners can also be used.
  • microphone 2 instead of the individual microphone 2, several, preferably two, microphones can also be attached, which are either arranged mechanically antiparallel or whose microphone membranes can be electrically polarized in opposite directions.
  • the effective distance between the two is vanishingly short, so that the duration of the sound between speaker membrane 7 and microphone phon 2 becomes negligible. There is therefore no dead time in the negative feedback circuit (see FIG. 1), which brings about a decisive improvement in the stability behavior of the control circuit compared to previously known arrangements.
  • the stability can be additionally increased by appropriate setting of the PI controller 5, it making sense to limit the frequency increase to very low frequencies (so-called counter).
  • a stationary plate 10 is arranged perpendicular to the direction of movement 9 in the area of the microphone 2 in front of the loudspeaker membrane 7.
  • the surface 11 of the loudspeaker membrane 7 covered by the plate 10 is drawn in with dashed lines.
  • the area 11 is approximately a quarter of the total area of the speaker diaphragm 7.
  • the microphone 2 is located approximately in the middle of the area 11.
  • the distance of the plate 10 from the edge 8 of the speaker diaphragm 7 is approximately 1 cm at its maximum deflection.
  • the plate 10 results in an improved signal-to-noise ratio of the sound signal picked up by the microphone 2.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

The invention relates to an arrangement for applying acoustic feedback to loudspeakers, with at least one microphone 2, which supplies a voltage proportional to the sound pressure generated by the loudspeaker 1; with a microphone amplifier 3; with a summing device 4, which adds the amplified microphone voltage in antiphase to the driving signal for the loudspeaker 1; with a PI controller 5, connected after the summing device 4; and with a power amplifier 6, connected after said controller, for driving the loudspeaker 1. In accordance with the invention, the microphone 2 is fitted on the loudspeaker diaphragm. <IMAGE>

Description

Die Erfindung betrifft eine Anordnung zur akustischen Gegenkopplung von Lautsprechern mit zumindest einem Mikrophon, das eine dem vom Lautsprecher erzeugten Schalldruck proportionale Spannung liefert, mit einem Mikrophonverstärker, mit einer Summierstelle, welche die verstärkte Mikrophonspannung gegenphasig zum Ansteuersignal des Lautsprechers addiert, mit einem der Summierstelle nachgeschalteten PI-Regler sowie mit einem nachfolgenden Leistungsverstärker zur Ansteuerung des Lautsprechers. Durch eine solche Gegenkopplung wird eine Verbesserung des Frequenzganges, des Klirrfaktors und der Impulstreue des Lautsprechers erzielt, was zu einer naturgetreuen Wiedergabe führt.The invention relates to an arrangement for acoustic negative feedback of loudspeakers with at least one microphone, which supplies a voltage proportional to the sound pressure generated by the loudspeaker, with a microphone amplifier, with a summing point, which adds the amplified microphone voltage in phase opposition to the control signal of the loudspeaker, with one downstream of the summing point PI controller and with a subsequent power amplifier to control the loudspeaker. Such a negative feedback leads to an improvement in the frequency response, the distortion factor and the pulse fidelity of the loudspeaker, which leads to a lifelike reproduction.

Es ist eine Lautsprecherschaltung mit akustischer Gegenkopplung bekannt, bei der das Gegenkopplungssignal mit einem Mikrophon aus dem Schallfeld vor dem Lautsprecher gewonnen wird, dieses Signal gegenphasig zum Ansteuersignal des Lautsprechers addiert und die Summenspannung über einen Verstärker dem Lautsprecher zugeführt wird (Deutsche Offenlegungsschrift 31 37 747). Das Mikrophon ist dabei im Abstand vor dem Lautsprecher angeordnet. Die sich daraus ergebende Laufzeit des Schalls vom Lautsprecher zum Mikrophon wirkt sich innerhalb des Regelkreises als stark frequenzproportionale, negative Phasendrehung aus. Dies führt schon bei relativ tiefen Frequenzen zu einer mangelhaften Stabilität des Regelkreises, was sich in einer Schwingungsneigung der Schaltung äußert. Diesem Problem wird durch gezielte Einstellung des Frequenzgangs des offenen Regelkreises zu begegnen versucht.A loudspeaker circuit with acoustic negative feedback is known, in which the negative feedback signal is obtained with a microphone from the sound field in front of the loudspeaker, this signal is added in phase opposition to the control signal of the loudspeaker and the sum voltage is fed to the loudspeaker via an amplifier (German Offenlegungsschrift 31 37 747). . The microphone is spaced in front of the speaker. Which are presented The resulting propagation time of the sound from the loudspeaker to the microphone has an effect in the control loop as a frequency shift, negative phase shift. Even at relatively low frequencies, this leads to inadequate stability of the control loop, which manifests itself in the tendency of the circuit to oscillate. Attempts are being made to counter this problem by specifically setting the frequency response of the open control loop.

Es ist auch bereits vorgeschlagen worden, ein stabiles Arbeiten eines Gegenkopplungskreises unter anderem dadurch zu erreichen, daß der maximale Abstand des Mikrophons von der Membran des Lautsprechers etwa ein Viertel der Wellenlänge der höchsten gegenzukoppelnden Frequenz beträgt und der minimale Abstand größer als die maximale Amplitude der Lautsprechermembran ist (Deutsche Offenlegungsschrift 21 41 141). Letztere Bedingung ist notwendig, um ein Anschlagen der Lautsprechermembran am Mikrophon zu verhindern. Insbesondere bei Verwendung moderner, langhubiger Tiefton-Lautsprechersysteme ergibt sich hieraus ein Mindestabstand zwischen Mikrophon und Lautsprechermembran im Zentimeterbereich.It has also already been proposed to achieve stable operation of a negative feedback circuit, inter alia, in that the maximum distance of the microphone from the membrane of the loudspeaker is approximately a quarter of the wavelength of the highest frequency to be negative-coupled and the minimum distance is greater than the maximum amplitude of the loudspeaker membrane is (German Offenlegungsschrift 21 41 141). The latter condition is necessary to prevent the loudspeaker membrane from hitting the microphone. Particularly when using modern, long-throw bass speaker systems, this results in a minimum distance between the microphone and the speaker diaphragm in the centimeter range.

Nachteilig bei den bekannten Verfahren zur akustischen Gegenkopplung von Lautsprechern ist, daß sich aus den unvermeidlichen Laufzeiten des Schalls vom Lautsprecher zum Mikrophon grundsätzlich eine mangelhafte Stabilität des Regelkreises ergibt, die nur noch schwer beherrschbar ist. Darüberhinaus ergeben sich durch den sich ständig verändernden Abstand zwischen Lautsprechermembran und Mikrophon zusätzliche Amplituden- und Intermodulationsverzerrungen. Da im Bereich vor der Lautsprechermembran starke Luftströmungen auftreten, nimmt das Mikrophon ferner unerwünschte Störgeräusche auf.A disadvantage of the known methods for acoustic negative feedback from loudspeakers is that the inevitable transit times of the sound from the loudspeaker to the microphone generally result in an inadequate stability of the control loop, which is difficult to control. In addition, the constantly changing distance between the loudspeaker membrane and the microphone results in additional amplitude and intermodulation distortions. Since strong air currents occur in the area in front of the loudspeaker diaphragm, the microphone also picks up unwanted noise.

Der vorliegenden Erfindung liegt die Aufgabe zugrunde, eine Anordnung zur akustischen Gegenkopplung von Lautsprechern vorzuschlagen, die die erwähnten Nachteile nicht aufweist; insbesondere soll sich der Gegenkopplungskreis durch eine verbesserte Stabilität auszeichnen.The present invention has for its object to propose an arrangement for acoustic negative feedback of speakers that does not have the disadvantages mentioned; in particular, the negative feedback circuit should be characterized by improved stability.

Bei der Lösung dieser Aufgabe wird von einer Anordnung zur akustischen Gegenkopplung von Lautsprechern gemäß dem Oberbegriff des Patentanspruchs 1 ausgegangen und gelöst wird sie dadurch, daß das Mikrophon auf der Lautsprechermembran angebracht ist. Damit bewegt sich das Mikrophon mit der Lautsprechermembran mit; der effektive Abstand zwischen beiden wird praktisch auf Null reduziert. Die Laufzeit des Schalls zwischen Lautsprechermembran und Mikrophon ist vernachlässigbar, sodaß eine negative Auswirkung auf das Stabilitätsverhalten des Gegenkopplungskreises ausgeschlossen ist. Die erfindungsgemäße Anordnung gestattet es somit erstmals, das Prinzip der akustischen Gegenkopplung mittels eines aus dem Schallfeld des Lautsprechers gewonnenen Signals einzusetzen, ohne damit gleichzeitig nur schwer beherrschbare Probleme hinsichtlich der Stabilität des Regelkreises in Kauf nehmen zu müssen. Amplituden- und Intermodulationsverzerrungen sind wegen der unveränderlichen Lage des Mikrophons auf der Lautsprechermembran ebenfalls ausgeschlossen. Da sich das Mikrophon nicht mehr im Bereich starker Luftströmungen befindet, nimmt es auch weniger Störgeräusche auf.In solving this problem, an arrangement for acoustic negative feedback of loudspeakers is assumed and is achieved in that the microphone is attached to the loudspeaker diaphragm. The microphone thus moves with the loudspeaker membrane; the effective distance between the two is practically reduced to zero. The propagation time of the sound between the loudspeaker membrane and the microphone is negligible, so that a negative effect on the stability behavior of the negative feedback circuit is excluded. The arrangement according to the invention thus makes it possible for the first time to use the principle of acoustic negative feedback by means of a signal obtained from the sound field of the loudspeaker, without at the same time having to accept difficult control problems with regard to the stability of the control loop. Amplitude and intermodulation distortions are also excluded due to the unchangeable position of the microphone on the loudspeaker membrane. Since the microphone is no longer in the area of strong air currents, it also absorbs less noise.

Zweckmäßigerweise ist das Mikrophon auf der Vorderseite der Lautsprechermembran angebracht. Hierdurch wird eine besonders gute Übereinstimmung zwischen abgestrahltem Schall und elektrischem Signal des Mikrophons, insbesondere bei geschlossenen Lautsprecherboxen, erzielt.The microphone is expediently attached to the front of the loudspeaker membrane. This results in a particularly good correspondence between the emitted sound and the electrical signal of the microphone, in particular in the case of closed loudspeaker boxes.

Zur Minimierung von Membran-Nahfeld-Interferenzen und störenden Einflüssen durch Partialschwingungen der Membranoberfläche ist in vorteilhafter Ausgestaltung der Erfindung das Mikrophon im Bereich des Randes der Lautsprechermembran angebracht.In order to minimize diaphragm near-field interference and disruptive influences due to partial vibrations of the diaphragm surface, the microphone is attached in an advantageous embodiment of the invention in the region of the edge of the loudspeaker diaphragm.

Wegen ihrer kleinen Abmessungen und ihres geringen Ge-3ewichtes bei gleichzeitig hervorragenden Übertragungseigenschaften finden vorteilhaft Elektret-Mikrophone zur Anbringung auf der Lautsprechermembran Verwendung.Because of their small dimensions and their low weight combined with excellent transmission properties, electret microphones are advantageously used for mounting on the loudspeaker membrane.

Da ein Elektret-Mikrophon bei einer Bewegung senkrecht zu seiner Mikrophonmembran auch als Beschleunigungsaufnehmer wirkt, ist dessen Membran zweckmäßigerweise in der Bewegungsrichtung der Lautsprechermembran angebracht.Since an electret microphone also acts as an accelerometer during a movement perpendicular to its microphone membrane, its membrane is expediently attached in the direction of movement of the loudspeaker membrane.

Vorteilhaft sind anstelle des einzelnen Mikrophons zwei gleichartige Mikrophone mechanisch antiparallel angeordnet, wobei deren Mikrophonspannungen-elektrisch addiert werden. Hierdurch wird eine weitgehende Kompensation von Körperschall erreicht.Instead of the individual microphone, two identical microphones are advantageously arranged mechanically antiparallel, with their microphone voltages being added electrically. This largely compensates for structure-borne noise.

In weiterer, vorteilhafter Ausgestaltung der Erfindung ist vor der Lautsprechermembran im Bereich des Mikrophons eine ortsfeste Platte angeordnet. Zum einen schattet diese Platte nicht vom Lautsprecher erzeugte Fremdgeräusche ab, zum anderen bewirkt sie infolge der Schallreflexionen an ihrer der Lautsprechermembran gegenüberliegenden Oberfläche eine Erhöhung des Schalldrucks im Bereich des Mikrophons; hierdurch wird das Verhältnis zwischen Stör- und Nutzsignal des Mikrophons wirksam verbessert.In a further advantageous embodiment of the invention, a stationary plate is arranged in front of the loudspeaker membrane in the area of the microphone. On the one hand, this plate does not shade external noises generated by the loudspeaker, on the other hand it causes an increase in the sound pressure in the surface due to the sound reflections on its surface opposite the loudspeaker membrane Area of the microphone; this effectively improves the ratio between the interference signal and the useful signal of the microphone.

Zweckmäßigerweise ist die ortsfeste Platte im wesentlichen senkrecht zur Bewegungsrichtung der Lautsprechermembran angeordnet.The stationary plate is expediently arranged essentially perpendicular to the direction of movement of the loudspeaker diaphragm.

In einer bevorzugten Ausführung der Erfindung deckt die feststehende Platte etwa ein Viertel der Fläche der Lautsprechermembran ab, und das Mikrophon befindet sich ungefähr in der Mitte dieser abgedeckten Fläche. Durch diese Dimensionierung wird bereits eine deutliche Verbesserung des Störabstandes des Mikrophons erzielt, ohne dabei die freie Schallabstrahlung des Lautsprechers zu sehr zu behindern.In a preferred embodiment of the invention, the fixed plate covers about a quarter of the area of the loudspeaker diaphragm and the microphone is located approximately in the middle of this covered area. This dimensioning already achieves a significant improvement in the signal-to-noise ratio of the microphone without too much interference with the free sound radiation from the loudspeaker.

Eine gute Wirkung der Platte ergibt sich bei einem Mindestabstand zwischen Platte und bewegter Lautsprechermembran von etwa 1 cm.The plate works well with a minimum distance of around 1 cm between the plate and the moving speaker cone.

Die Erfindung wird nachstehend anhand der beigefügten Zeichnung näher erläutert. Es zeigen:

  • Fig. 1 eine Anordnung zur akustischen Gegenkopplung von Lautsprechern, in einem Prinzipschaltbild,
  • Fig. 2 einen Lautsprecher mit einem auf der Lautsprechermembran angebrachtem Mikrophon sowie vorgesetzter Platte, in einer stark vereinfachten, teilweise aufgeschnittenen Seitenansicht,
  • Fig. 3 den Lautsprecher gemäß Figur 2, in einer Vorderansicht.
The invention is explained below with reference to the accompanying drawings. Show it:
  • 1 shows an arrangement for acoustic negative feedback of loudspeakers, in a basic circuit diagram,
  • 2 shows a loudspeaker with a microphone attached to the loudspeaker membrane and a front plate, in a greatly simplified, partially cut-away side view,
  • Fig. 3 shows the speaker of Figure 2, in a front view.

In Figur 1 ist das Prinzip der akustischen Gegenkopplung eines Lautsprechers 1 dargestellt. Im Schallfeld des Lautsprechers 1 befindet sich ein Mikrophon 2, das eine dem Schalldruck proportionale Spannung liefert. Nach Verstärkung. mittels eines Mikrophonverstärkers 3 wird diese Spannung in einer Summierstelle 4 gegenphasig zum Ansteuersignal des Lautsprechers 1 addiert. Der Summierstelle nachgeschaltet ist ein PI-Regler 5, der so eingestellt ist, daß er eine Anhebung der tiefen Frequenzen bewirkt, was zur Stabilität des Regelkreises beiträgt. Ein Leistungsverstärker 6 verstärkt das Ansteuersignal soweit, wie es zum Betrieb des Lautsprechers 1 erforderlich ist.The principle of acoustic negative feedback of a loudspeaker 1 is shown in FIG. In the sound field of the loudspeaker 1 there is a microphone 2 which supplies a voltage proportional to the sound pressure. After reinforcement. by means of a microphone amplifier 3 this voltage is added in a summing point 4 in phase opposition to the control signal of the loudspeaker 1. Downstream of the summing point is a PI controller 5, which is set in such a way that it increases the low frequencies, which contributes to the stability of the control loop. A power amplifier 6 amplifies the control signal as far as is required to operate the loudspeaker 1.

Wie Figur 2 beispielhaft verdeutlicht, ist das Mikrophon 2 direkt auf der Vorderseite der Lautsprechermembran 7 angebracht. Gezeigt ist hier eine Anordnung unter Verwendung eines kleinen Elektret-Mikrophones im Bereich des.Randes 8 der Lautsprechermembran 7, dessen Membran in Bewegungsrichtung 9 der Lautsprechermembran 7 angebracht ist. Die Befestigung des Mikrophons 2 auf der Oberfläche der Lautsprechermembran 7 geschieht im einfachsten Falle mittels Klebung; es können jedoch auch zusätzliche Befestigungsmittel verwendet werden.As exemplified in FIG. 2, the microphone 2 is attached directly to the front of the loudspeaker membrane 7. An arrangement is shown here using a small electret microphone in the area of the edge 8 of the loudspeaker membrane 7, the membrane of which is attached to the loudspeaker membrane 7 in the direction of movement 9. The attachment of the microphone 2 on the surface of the speaker diaphragm 7 is done in the simplest case by gluing; however, additional fasteners can also be used.

Anstelle des einzelnen Mikrophons 2 können auch mehrere, vorzugsweise zwei Mikrophone angebracht werden, die entweder mechanisch antiparallel angeordnet oder deren Mikrophonmembranen entgegengesetzt elektrisch polarisiert sein können.Instead of the individual microphone 2, several, preferably two, microphones can also be attached, which are either arranged mechanically antiparallel or whose microphone membranes can be electrically polarized in opposite directions.

Durch die Anbringung des Mikrophons 2 unmittelbar auf der Lautsprechermembran 7 ist der wirksame Abstand zwischen beiden verschwindend gering, sodaß die Laufzeit des Schalls zwischen Lautsprechermembran 7 und Mikrophon 2 vernachlässigbar wird. Im Gegenkopplungskreis (vgl. Figur 1) tritt somit keine Totzeit auf, was eine gegenüber bisher bekannten Anordnungen entscheidende Verbesserung des Stabilitätsverhalten des Regelkreises bewirkt. Die Stabilität kann durch entsprechende Einstellung des PI-Reglers 5 noch zusätzlich erhöht werden, wobei es sinnvoll ist, die Frequenzanhebung zu sehr tiefen Frequenzen hin zu begrenzen (sogenannter Gegenhalt).By attaching the microphone 2 directly on the speaker membrane 7, the effective distance between the two is vanishingly short, so that the duration of the sound between speaker membrane 7 and microphone phon 2 becomes negligible. There is therefore no dead time in the negative feedback circuit (see FIG. 1), which brings about a decisive improvement in the stability behavior of the control circuit compared to previously known arrangements. The stability can be additionally increased by appropriate setting of the PI controller 5, it making sense to limit the frequency increase to very low frequencies (so-called counter).

Bei dem hier gezeigten Ausführungsbeispiel der Erfindung ist im Bereich des Mikrophons 2 vor der Lautsprechermembran 7 eine ortsfeste Platte 10 senkrecht zur Bewegungsrichtung 9 angeordnet. In Figur 3 ist die von der Platte 10 abgedeckte Fläche 11 der Lautsprechermembran 7 mit Strichlinien eingezeichnet. Die Fläche 11 beträgt etwa ein Viertel der Gesamtfläche der Lautsprechermembran 7. Das Mikrophon 2 befindet sich ungefähr in der Mitte der Fläche 11. Der Abstand der Platte 10 vom Rand 8 der Lautsprechermembran 7 beträgt bei deren maximaler Auslenkung ungefähr 1 cm. Wie oben bereits erläutert, ergibt sich durch die Platte 10 ein verbesserter Störabstand des vom Mikrophon 2 aufgenommenen Schallsignals.In the embodiment of the invention shown here, a stationary plate 10 is arranged perpendicular to the direction of movement 9 in the area of the microphone 2 in front of the loudspeaker membrane 7. In FIG. 3, the surface 11 of the loudspeaker membrane 7 covered by the plate 10 is drawn in with dashed lines. The area 11 is approximately a quarter of the total area of the speaker diaphragm 7. The microphone 2 is located approximately in the middle of the area 11. The distance of the plate 10 from the edge 8 of the speaker diaphragm 7 is approximately 1 cm at its maximum deflection. As already explained above, the plate 10 results in an improved signal-to-noise ratio of the sound signal picked up by the microphone 2.

Zusammenstellung der verwendeten BezugsziffernCompilation of the reference numbers used

  • 1 Lautsprecher1 speaker
  • 2 Mikrophon2 microphone
  • 3 Mikrophonverstärker3 microphone amplifiers
  • 4 Summierstelle4 summing point
  • 5 PI-Regler5 PI controllers
  • 6 Leistungsverstärker6 power amplifiers
  • 7 Lautsprechermembran (von 1)7 speaker diaphragm (of 1)
  • 8 Rand (von 7)8 rand (of 7)
  • 9 Bewegungsrichtung (von 7)9 Direction of movement (of 7)
  • 10 Platte10 plate
  • 11 Fläche (auf 7)11 surface (on 7)

Claims (10)

1. Anordnung zur akustischen Gegenkopplung von Lautsprechern mit zumindest einem Mikrophon, das eine dem vom Lautsprecher erzeugten Schalldruck proportionale Spannung liefert, mit einem Mikrophonverstärker, mit einer Summierstelle, welche die verstärkte Mikrophonspannung gegenphasig zum Ansteuersignal des Lautsprechers addiert, mit einem der Summierstelle nachgeschalteten PI-Regler sowie mit einem nachfolgenden Leistungsverstärker zur Ansteuerung des Lautsprechers, dadurch gekennzeichnet , daß das Mikrophon (2) auf der Lautsprechermembran (7) angebracht ist.1. Arrangement for acoustic negative feedback of loudspeakers with at least one microphone, which supplies a voltage proportional to the sound pressure generated by the loudspeaker, with a microphone amplifier, with a summing point, which adds the amplified microphone voltage in phase opposition to the control signal of the loudspeaker, with a PI connected downstream of the summing point. Regulator and with a subsequent power amplifier for controlling the loudspeaker, characterized in that the microphone (2) is attached to the loudspeaker membrane (7). 2. Anordnung nach Anspruch 1, dadurch gekennzeichnet , daß das Mikrophon (2) auf der Vorderseite der Lautsprechermembran (7) angebracht ist.2. Arrangement according to claim 1, characterized in that the microphone (2) on the front of the speaker membrane (7) is attached. 3. Anordnung nach Anspruch 1 oder 2, dadurch gekennzeichnet , daß das Mikrophon (2) im Bereich des Randes (8) der Lautsprechermembran (7) angebracht ist.3. Arrangement according to claim 1 or 2, characterized in that the microphone (2) in the region of the edge (8) of the loudspeaker membrane (7) is attached. 4. Anordnung nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet , daß als Mikrophon (2) ein Elektret-Mikrophon Verwendung findet.4. Arrangement according to one of claims 1 to 3, characterized in that an electret microphone is used as the microphone (2). 5. Anordnung nach Anspruch 4, dadurch gekennzeichnet , daß die Membran des Mikrophons (2) in der Bewegungsrichtung (9) der Lautsprechermembran (7) angebracht ist.5. Arrangement according to claim 4, characterized in that the membrane of the micro Phons (2) in the direction of movement (9) of the speaker membrane (7) is attached. 6. Anordnung nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, daß ein zweites, gleichartiges,mechanisch antiparallel angeordnetes Mikrophon vorgesehen ist und die Mikrophonspannungen beider Mikrophone elektrisch addiert werden.6. Arrangement according to one of claims 1 to 5, characterized in that a second, similar, mechanically antiparallel microphone is provided and the microphone voltages of both microphones are added electrically. 7. Anordnung nach einem der Ansprüche 1 bis 6, da - durch gekennzeichnet , daß vor der Lautsprechermembran (7) im Bereich des Mikrophons (2) eine ortsfeste Platte (10) angeordnet ist.7. Arrangement according to one of claims 1 to 6, characterized in that a fixed plate (10) is arranged in front of the loudspeaker membrane (7) in the region of the microphone (2). 8. Anordnung nach Anspruch 7, dadurch gekennzeichnet , daß die Platte (10) im wesentlichen senkrecht zur Bewegungsrichtung (9) der Lautsprechermembran (7) angeordnet ist.8. Arrangement according to claim 7, characterized in that the plate (10) is arranged substantially perpendicular to the direction of movement (9) of the loudspeaker diaphragm (7). 9. Anordnung nach Anspruch 7 oder 8, dadurch gekennzeichnet, daß die Platte (10) nahezu ein Viertel der Fläche der Lautsprechermembran (7) abdeckt, und das Mikrophon (2) im Bereich der Mitte dieser abgedeckten Fläche (11) vorgesehen ist.9. Arrangement according to claim 7 or 8, characterized in that the plate (10) covers almost a quarter of the area of the loudspeaker diaphragm (7), and the microphone (2) is provided in the region of the center of this covered area (11). 10. Anordnung nach einem der Ansprüche 7 bis 9, da - durch gekennzeichnet , daß der Mindestabstand der Platte (10) von der maximalen Auslenkung der Lautsprechermembran (7) 1 cm beträgt.10. Arrangement according to one of claims 7 to 9, characterized in that the minimum distance of the plate (10) from the maximum deflection of the loudspeaker diaphragm (7) is 1 cm.
EP85109881A 1984-08-08 1985-08-06 Arrangement for the acoustic feedback of loudspeakers Withdrawn EP0171065A3 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3429147 1984-08-08
DE19843429147 DE3429147C2 (en) 1984-08-08 1984-08-08 Arrangement for acoustic feedback of loudspeakers

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EP0171065A2 true EP0171065A2 (en) 1986-02-12
EP0171065A3 EP0171065A3 (en) 1986-11-20

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EP85109881A Withdrawn EP0171065A3 (en) 1984-08-08 1985-08-06 Arrangement for the acoustic feedback of loudspeakers

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EP (1) EP0171065A3 (en)
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DE4139681A1 (en) * 1991-12-02 1992-07-02 Czerny Heribert Bass loudspeaker drive unit - uses diaphragm suspension of negligible stiffness and PID controller to compensate for diaphragm deflection
FR2673800A1 (en) * 1991-03-07 1992-09-11 Lan Yan Fock Alain Electroacoustic device for sound reproduction, electronically servo-controlled, using a horn loudspeaker equipped with microphones
GB2268356A (en) * 1992-06-23 1994-01-05 Itzhak Chavet High-fidelity loudspeaker.
DE4334040A1 (en) * 1993-10-06 1995-04-13 Klippel Wolfgang Circuit arrangement for the automatic correction of the transfer characteristics of electrodynamic sound transmitters without additional mechanical or acoustic sensor
GB2292854A (en) * 1994-08-12 1996-03-06 Motorola Ltd Control of audio output using motional feedback and ambient noise detection
WO1997003536A1 (en) * 1995-07-07 1997-01-30 University Of Salford Loudspeaker circuit with means for monitoring the pressure at the speaker diaphragm, means for monitoring the velocity of the speaker diaphragm and a feedback circuit
WO1997009847A1 (en) * 1995-09-02 1997-03-13 New Transducers Limited Panel-form loudspeakers
EP0941013A1 (en) * 1998-03-05 1999-09-08 Alcatel Radio telecommunication terminal

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EP2667634B1 (en) * 2012-05-25 2015-07-08 AKG Acoustics GmbH Earphone with active suppression of ambient noise

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2673800A1 (en) * 1991-03-07 1992-09-11 Lan Yan Fock Alain Electroacoustic device for sound reproduction, electronically servo-controlled, using a horn loudspeaker equipped with microphones
DE4139681A1 (en) * 1991-12-02 1992-07-02 Czerny Heribert Bass loudspeaker drive unit - uses diaphragm suspension of negligible stiffness and PID controller to compensate for diaphragm deflection
GB2268356A (en) * 1992-06-23 1994-01-05 Itzhak Chavet High-fidelity loudspeaker.
DE4334040A1 (en) * 1993-10-06 1995-04-13 Klippel Wolfgang Circuit arrangement for the automatic correction of the transfer characteristics of electrodynamic sound transmitters without additional mechanical or acoustic sensor
GB2292854B (en) * 1994-08-12 1999-08-25 Motorola Ltd Electronic audio device and method of operation
GB2292854A (en) * 1994-08-12 1996-03-06 Motorola Ltd Control of audio output using motional feedback and ambient noise detection
US5771297A (en) * 1994-08-12 1998-06-23 Motorola, Inc. Electronic audio device and method of operation
WO1997003536A1 (en) * 1995-07-07 1997-01-30 University Of Salford Loudspeaker circuit with means for monitoring the pressure at the speaker diaphragm, means for monitoring the velocity of the speaker diaphragm and a feedback circuit
WO1997009847A1 (en) * 1995-09-02 1997-03-13 New Transducers Limited Panel-form loudspeakers
EP0941013A1 (en) * 1998-03-05 1999-09-08 Alcatel Radio telecommunication terminal
WO1999045743A1 (en) * 1998-03-05 1999-09-10 Alcatel Radio telecommunication terminal
FR2775861A1 (en) * 1998-03-05 1999-09-10 Alsthom Cge Alcatel RADIOTELECOMMUNICATION TERMINAL
US6564072B1 (en) 1998-03-05 2003-05-13 Alcatel Radio telecommunication terminal

Also Published As

Publication number Publication date
DE3429147C2 (en) 1987-04-02
DE3429147A1 (en) 1986-02-20
EP0171065A3 (en) 1986-11-20

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