EP0366109A2 - Method and device for linearizing the frequency response of a loudspeaker system - Google Patents

Method and device for linearizing the frequency response of a loudspeaker system Download PDF

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Publication number
EP0366109A2
EP0366109A2 EP19890119821 EP89119821A EP0366109A2 EP 0366109 A2 EP0366109 A2 EP 0366109A2 EP 19890119821 EP19890119821 EP 19890119821 EP 89119821 A EP89119821 A EP 89119821A EP 0366109 A2 EP0366109 A2 EP 0366109A2
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EP
European Patent Office
Prior art keywords
loudspeaker
operational amplifier
loudspeaker system
signal
voltage
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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.)
Ceased
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EP19890119821
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German (de)
French (fr)
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EP0366109A3 (en
Inventor
Michael Walker
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Alcatel Lucent Deutschland AG
Alcatel Lucent NV
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Alcatel SEL AG
Alcatel NV
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Application filed by Alcatel SEL AG, Alcatel NV filed Critical Alcatel SEL AG
Publication of EP0366109A2 publication Critical patent/EP0366109A2/en
Publication of EP0366109A3 publication Critical patent/EP0366109A3/en
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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
    • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
    • 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 a method and a device for linearizing the frequency response of a loudspeaker system, in particular for suppressing resonance phenomena.
  • a phase and amplitude controlled loudspeaker with any number of paths is known.
  • the aim of this regulation is to linearize the frequency response (phase + amplitude) of a sound transducer.
  • the sound transducer can be a single speaker, but also an arrangement consisting of several speakers.
  • the control loop consists of the elements power amplifier, passive crossover, summing amplifier and one or more loudspeakers.
  • the controlled variable is the voltage that controls the loudspeakers and is fed back at the input of the power amplifier.
  • An operational amplifier connected to a feedback network is located in the feedback.
  • the controlled variable can also be derived from other sensors (see Figure 1 of the published specification).
  • the known regulated loudspeaker has the disadvantage that only a voltage negative feedback is carried out here, which has little influence on the natural dynamics of the loudspeaker. If a loudspeaker is operated, for example, at a frequency that is very close to a resonance point of the loudspeaker housing, the power emitted by the loudspeaker changes very strongly, but this is hardly noticeable in the control voltage. Under such operating conditions, the known regulation has little effect.
  • the object of the invention is to linearize the frequency response of a speaker or speaker system so that the influence of mechanical resonances caused by the geometric dimensions of the housing is compensated.
  • the power emitted by the loudspeaker or loudspeaker system should become frequency-independent.
  • the method and device according to the invention have the advantage that the control variable is not the voltage output by a power amplifier, but the impedance of the loudspeaker system.
  • the impedance of a loudspeaker system shows sharp peaks in the vicinity of mechanical resonance points, it being irrelevant whether the resonance of the loudspeaker or the housing is intrinsic.
  • The serves as a measure of the impedance of the speaker system current flowing through the speaker system.
  • the power emitted by the loudspeaker system is regulated by controlling the current flowing through the loudspeaker system (negative current feedback)
  • Another advantage is the fact that by feedback of a filtered signal proportional to the impedance of the loudspeaker system, the frequency response for other frequency ranges, especially for frequencies below 200 Hz, is linearized or brought into a desired course.
  • Sound transducers also called loudspeaker systems in the following, are intended for control with constant electrical power in a large frequency range radiate an acoustic power independent of the frequency.
  • the sound pressure p of an idealized loudspeaker is plotted against the frequency f.
  • the sound pressure p is independent of the frequency for a large frequency range (reference number 1).
  • Curve 2 in Figure 1b shows the sound pressure of a real loudspeaker system depending on the frequency.
  • Mechanical resonances of the loudspeaker system occur at the frequencies designated 3 and 4. In the vicinity of such a resonance point, the sound pressure initially drops sharply, then passes through a minimum, then exceeds the desired value and then falls back to the desired value. Sound pressure curves like curve 2 in FIG. 1b are undesirable for sound converters.
  • Fig. 1c again represents the sound pressure of an (ideal) loudspeaker depending on the frequency. Measures that are discussed in connection with FIG. 2 cause the low frequencies to be raised (5) and the upper limit frequency to be pushed further out (6).
  • a power amplifier is designated by 10, which generates an electrical power required to control a loudspeaker system 20.
  • the current flowing through the loudspeaker system 20 is measured using a measuring resistor 21.
  • the voltage signal at the measuring resistor 21 is fed to a first operational amplifier, designated 30.
  • 33 is a high-pass filter, which is the voltage on the speaker system 20 with the connects inverting input of operational amplifier 30.
  • a second operational amplifier 40 amplifies a difference signal which is formed from the output signal of the operational amplifier 30 and the voltage applied to the loudspeaker system.
  • the output of the operational amplifier 30 and the non-inverting input of the operational amplifier 40 are connected to one another via a third high-pass filter 22.
  • the voltage signal is applied to the inverting input of the operational amplifier 40 via a second high-pass filter 45 and an adder 42.
  • a low pass 44 which is superimposed at the summation point 42 on the signal from the high pass 45.
  • the output voltage of the operational amplifier 40 is added in an adder 16 to a low-frequency voltage to be amplified and applied to the input of the power amplifier 10.
  • the entire circuit represents a negative current feedback and operates as follows:
  • the current driving the loudspeaker system 20 generates a voltage drop in the measuring resistor 21, which is amplified by the operational amplifier 30.
  • the amplification factor of the amplifier 30 is selected such that its output voltage in operating states in which there are no mechanical resonances in the loudspeaker system 20 is the same in terms of amount and phase of the voltage on the loudspeaker system.
  • the voltage at the loudspeaker system passes through the second high-pass filter 45 to the inverting input of the amplifier 40, the output voltage of the amplifier 30 via the high-pass filter 22 to the non-inverting input of the amplifier 40. In the normal case, the output signal of the operational amplifier 40 is therefore zero.
  • the system vibrates with a significantly lower power consumption, but the resulting measurable electrical impedance of the voice coil increases - excessive resonance in the parallel resonant circuit.
  • the voltage driving the speaker system remains the same, while the current through the speaker system decreases sharply, i.e. in other words, the input signal of the operational amplifier 30 becomes smaller.
  • a differential signal that is not equal to zero is now present at the operational amplifier 40.
  • This signal is amplified by the operational amplifier 40 and superimposed at the summation point 16 of the low-frequency voltage to be amplified. If the high-pass filters 22, 33 and 45 are selected appropriately, the two signals are superimposed so that the sound power emitted by the loudspeaker system remains constant.
  • the measures described also improve the pulse behavior of the loudspeaker system, since the mechanical vibrations excited by pulses are quickly dampened as a result of the negative feedback.
  • the circuit principle shown in Fig. 2 has yet another advantage. Frequently, when using inexpensive sound transducers, the low frequencies below 200 Hz are missing in the reproduction spectrum. The sound pressure drops significantly at frequencies below 200 Hz, which makes the reproduction sound garish. The impedance of the speaker system also decreases at these frequencies. If the lower cut-off frequency of the high-pass filter 45 is selected to be higher than that of the filter 22, a phase rotation of 180 ° occurs below the cut-off frequency in the correction signal, which causes positive feedback in this frequency range (cf. FIGS. 1c, 5). This measure can Sound radiation behavior of the speaker system can be improved at low frequencies. With the help of the filter 44, the sound radiation behavior at high frequencies can be influenced (cf. FIGS. 1c, 6).
  • FIG. 3 shows a circuit example for the basic circuit diagram according to FIG. 2.
  • the same reference numerals designate the same elements as in FIG. 1. All details of the circuit are omitted here, since the essence of the invention is not in the construction of the circuit but in the one used Principle lies.
  • the operational amplifier 30 is a symmetrically constructed amplifier. That is, the resistors 35 and the high-pass resistor 33 are the same, and the two resistors 34 and 36 are the same.

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

Abstract

Der Frequenzgang von Lautsprechersystemen läßt sich durch die Spannungsgegenkopplung in einfacher Weise linearisieren. Reine Spannungsgegenkopplungen haben jedoch den Nachteil, daß mechanische Resonanzerscheinungen des Lautsprechersystems nur unvollkommen kompensiert werden. Es werden ein Verfahren und eine Vorrichtung vorgeschlagen, bei welchen das Rückkopplungssignal aus der Impedanz des Lautsprechersystems gewonnen wird. Als Maß für die Impedanz des Lautsprechersystems dient der durch das Lautsprechersystem fließende Strom. Das der Impedanz entsprechende Signal gelangt nach Filterung auf den Eingang des Leistungsverstärkers zurück.The frequency response of loudspeaker systems can be linearized in a simple manner by means of negative voltage feedback. However, pure negative feedback has the disadvantage that mechanical resonance phenomena of the loudspeaker system are only incompletely compensated for. A method and a device are proposed in which the feedback signal is obtained from the impedance of the loudspeaker system. The current flowing through the speaker system serves as a measure of the impedance of the speaker system. After filtering, the signal corresponding to the impedance is returned to the input of the power amplifier.

Description

Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur Linearisierung des Frequenzganges eines Lautsprechersystems, insbesondere zur Unterdrückung von Resonanzerscheinungen.
Aus der DE-OS 36 37 666 ist ein Phasen- und Amplituden geregelter Lautsprecher mit beliebig vielen Wegen bekannt. Ziel dieser Regelung ist es, den Frequenzgang (Phase + Amplitude) eines Schallwandlers zu linearisieren. Der Schallwandler kann dabei ein einzelner Lautsprecher, aber auch eine aus mehreren Lautsprechern bestehende Anordnung sein. Der Regelkreis besteht aus den Elementen Leistungsverstärker, passive Frequenzweiche, Summierverstärker und einem oder mehreren Lautsprechern. Regelgröße ist die die Lautsprecher steuernde Spannung, die am Eingang des Leistungsverstärkers gegengekoppelt wird. In der Rückführung befindet sich ein mit einem Rückkopplungsnetzwerk beschalteter Operationsverstärker. Die Regelgröße kann auch aus anderen Gebern abgeleitet werden (siehe Figur 1 der Offenlegungsschrift).The invention relates to a method and a device for linearizing the frequency response of a loudspeaker system, in particular for suppressing resonance phenomena.
From DE-OS 36 37 666 a phase and amplitude controlled loudspeaker with any number of paths is known. The aim of this regulation is to linearize the frequency response (phase + amplitude) of a sound transducer. The sound transducer can be a single speaker, but also an arrangement consisting of several speakers. The control loop consists of the elements power amplifier, passive crossover, summing amplifier and one or more loudspeakers. The controlled variable is the voltage that controls the loudspeakers and is fed back at the input of the power amplifier. An operational amplifier connected to a feedback network is located in the feedback. The controlled variable can also be derived from other sensors (see Figure 1 of the published specification).

Der bekannte geregelte Lautsprecher hat den Nachteil, daß hier lediglich eine Spannungsgegenkopplung vorgenommen wird, die auf die Eigendynamik des Lautsprechers wenig Einfluß hat. Wird ein Lautsprecher bspw. mit einer Frequenz betrieben, die sehr nahe an einer Resonanzstelle des Lautsprechergehäuses liegt, so ändert sich die vom Lautsprecher abgestrahlte Leistung sehr stark, was sich aber in der Ansteuerspannung kaum bemerkbar macht. Unter solchen Betriebsbedingungen wirkt die bekannte Regelung nur wenig.The known regulated loudspeaker has the disadvantage that only a voltage negative feedback is carried out here, which has little influence on the natural dynamics of the loudspeaker. If a loudspeaker is operated, for example, at a frequency that is very close to a resonance point of the loudspeaker housing, the power emitted by the loudspeaker changes very strongly, but this is hardly noticeable in the control voltage. Under such operating conditions, the known regulation has little effect.

Aufgabe der Erfindung ist es, den Frequenzgang eines Lautsprechers oder Lautsprechersystems so zu linearisieren, daß der Einfluß mechanischer Resonanzen, verursacht durch die geometrischen Abmessungen des Gehäuses, kompensiert wird. Die vom Lautsprecher oder Lautsprechersystem abgestrahlte Leistung soll frequenzunabhängig werden. Diese Aufgabe wird gelöst durch ein Verfahren mit der Merkmalskombination des 1. Verfahrensanspruches und eine Vorrichtung mit der Merkmalskombination des 1. Vorrichtungsanspruches.The object of the invention is to linearize the frequency response of a speaker or speaker system so that the influence of mechanical resonances caused by the geometric dimensions of the housing is compensated. The power emitted by the loudspeaker or loudspeaker system should become frequency-independent. This object is achieved by a method with the combination of features of the 1st method claim and a device with the combination of features of the 1st device claim.

In den Unteransprüchen sind weitere Ausgestaltungen der Erfindung enthalten.Further embodiments of the invention are contained in the subclaims.

Verfahren und Vorrichtung gemäß der Erfindung haben den Vorteil, daß als Regelgröße nicht die von einem Leistungsverstärker abgegebene Spannung, sondern die Impedanz des Lautsprechersystems herangezogen wird. Die Impendanz eines Lautsprechersystems zeigt in der Nähe mechanischer Resonanzstellen scharfe Peaks, wobei es unerheblich ist, ob es sich um Eigenresonanzen des Lautsprechers oder um solche des Gehäuses handelt. Als Maß für die Impedanz des Lautsprechersystems dient der durch das Lautsprechersystem fließende Strom. Die vom Lautsprechersystem abgestrahlte Leistung wird durch eine Steuerung des durch das Lautsprechersystem fließenden Stromes geregelt (Stromgegenkopplung)The method and device according to the invention have the advantage that the control variable is not the voltage output by a power amplifier, but the impedance of the loudspeaker system. The impedance of a loudspeaker system shows sharp peaks in the vicinity of mechanical resonance points, it being irrelevant whether the resonance of the loudspeaker or the housing is intrinsic. The serves as a measure of the impedance of the speaker system current flowing through the speaker system. The power emitted by the loudspeaker system is regulated by controlling the current flowing through the loudspeaker system (negative current feedback)

Ein weiterer Vorteil ist darin zu sehen, daß durch Rückkopplung eines gefilterten, zur Impedanz des Lautsprechersystems proportionalen Signals der Frequenzgang auch für andere Frequenzbereiche, vor allem für Frequenzen unterhalb von 200 Hz, linearisiert oder in einen gewünschten Verlauf gebracht wird.Another advantage is the fact that by feedback of a filtered signal proportional to the impedance of the loudspeaker system, the frequency response for other frequency ranges, especially for frequencies below 200 Hz, is linearized or brought into a desired course.

Ein Ausführungsbeispiel der Erfindung wird im folgenden beschrieben und anhand der Figuren 1 bis 3 näher erläutert. Es zeigen

  • Fig. 1a den Schalldruck eines idealisierten Lautsprechers in Abhängigkeit von der Frequenz;
  • Fig. 1b den Schalldruck eines realen Lautsprechers in Abhängigkeit von der Frequenz;
  • Fig. 1c den Schalldruck eines Lautsprechers in Abhängigkeit von der Frequenz; Anhebung von Tiefen und Höhen;
  • Fig. 2 das Schaltungsprinzip zur Regelung der von einem Schallwandler abgestrahlten Leistung;
  • Fig. 3 ein Schaltungsbeispiel nach Figur 2.
An embodiment of the invention is described below and explained in more detail with reference to Figures 1 to 3. Show it
  • 1a shows the sound pressure of an idealized loudspeaker as a function of the frequency;
  • 1b the sound pressure of a real loudspeaker as a function of the frequency;
  • 1c the sound pressure of a loudspeaker as a function of the frequency; Raising lows and highs;
  • 2 shows the circuit principle for regulating the power emitted by a sound converter;
  • 3 shows a circuit example according to FIG. 2.

Schallwandler, im folgenden auch Lautsprechersysteme genannt, sollen bei Ansteuerung mit konstanter elektrischer Leistung in einem großen Frequenzbereich eine von der Frequenz unabhängige akustische Leistung abstrahlen. In Fig. 1 ist der Schalldruck p eines idealisierten Lautsprechers über der Frequenz f aufgetragen. Der Schalldruck p ist für einen großen Frequenzbereich unabhängig von der Frequenz (Bezugszeichen 1). Kurve 2 in Figur 1b gibt den Schalldruck eines realen Lautsprechersystems abhängig von der Frequenz wieder. Bei den mit 3 und 4 bezeichneten Frequenzen treten mechanische Resonanzen des Lautsprechersystems auf. In der Nähe einer solchen Resonanzstelle fällt der Schalldruck zunächst stark ab, durchläuft dann ein Minimum, übersteigt anschließend den gewünschten Wert und fällt dann auf den gewünschten Wert zurück. Schalldruckkurven wie die Kurve 2 in Fig. 1b sind für Schallwandler unerwünscht.Sound transducers, also called loudspeaker systems in the following, are intended for control with constant electrical power in a large frequency range radiate an acoustic power independent of the frequency. 1, the sound pressure p of an idealized loudspeaker is plotted against the frequency f. The sound pressure p is independent of the frequency for a large frequency range (reference number 1). Curve 2 in Figure 1b shows the sound pressure of a real loudspeaker system depending on the frequency. Mechanical resonances of the loudspeaker system occur at the frequencies designated 3 and 4. In the vicinity of such a resonance point, the sound pressure initially drops sharply, then passes through a minimum, then exceeds the desired value and then falls back to the desired value. Sound pressure curves like curve 2 in FIG. 1b are undesirable for sound converters.

In Fig. 1c ist mit 1 wiederum der Schalldruck eines (idealen) Lautsprechers abhängig von der Frequenz wiedergegeben. Maßnahmen, die im Zusammenhang mit Fig. 2 besprochen werden, bewirken, daß die tiefen Frequenzen angehoben werden (5) und die obere Grenzfrequenz weiter hinausgeschoben wird (6).In Fig. 1c, 1 again represents the sound pressure of an (ideal) loudspeaker depending on the frequency. Measures that are discussed in connection with FIG. 2 cause the low frequencies to be raised (5) and the upper limit frequency to be pushed further out (6).

Fig. 2 zeigt das Schaltungsprinzip zur Regelung der von einem Schallwandler abgestrahlten Leistung. Mit 10 ist ein Leistungsverstärker bezeichnet, der eine zur Ansteuerung eines Lautsprechersystems 20 erforderliche elektrische Leistung erzeugt. Der durch das Lautsprechersystem 20 fließende Strom wird mit Hilfe eines Meßwiderstandes 21 gemessen. Das am Meßwiderstand 21 liegende Spannungssignal wird einem mit 30 bezeichneten ersten Operationsverstärker zugeführt. Mit 33 ist ein Hochpaß bezeichnet, der die am Lautsprechersystem 20 liegende Spannung mit dem invertierenden Eingang des Operationsverstärkers 30 verbindet. Ein zweiter Operationsverstärker 40 verstärkt ein Differenzsignal, das aus dem Ausgangssignal des Operationsverstärkers 30 und der am Lautsprechersystem liegenden Spannung gebildet wird. Ausgang des Operationsverstärkers 30 und des nicht invertierenden Eingangs des Operationsverstärkers 40 sind über einen dritten Hochpaß 22 miteinander verbunden. Das Spannungssignal wird über einen zweiten Hochpaß 45 und einen Addierer 42 auf den invertierenden Eingang des Operationsverstärkers 40 gegeben. Im Rückkopplungszweig des Operationsverstärkers 40 liegt ein Tießpaß 44, der im Summationspunkt 42 dem aus dem Hochpaß 45 stammenden Signal überlagert wird. Die Ausgangsspannung des Operationsverstärkers 40 wird in einem Addierer 16 zu einer zu verstärkenden niederfrequenten Spannung addiert und auf den Eingang des Leistungsverstärkers 10 gegeben. Die gesamte Schaltung stellt eine Stromgegenkopplung dar und arbeitet wie folgt: Der das Lautsprechersystem 20 antreibende Strom erzeugt im Meßwiderstand 21 einen Spannungsabfall, der durch den Operationsverstärker 30 verstärkt wird. Der Verstärkungsfaktor des Verstärkers 30 ist so gewählt, daß seine Ausgangsspannung in Betriebszuständen, in denen keine mechanischen Resonanzen im Lautsprechersystem 20 auftreten, nach Betrag und Phase der Spannung am Lautsprechersystem gleich ist. Die Spannung am Lautsprechersystem gelangt über den zweiten Hochpaß 45 auf den invertierenden Eingang des Verstärkers 40, die Ausgangsspannung des Verstärkers 30 über den Hochpaß 22 auf den nicht invertierenden Eingang des Verstärkers 40. Im Normalfall ist damit das Ausgangssignal des Operationsverstärkers 40 gleich Null.2 shows the circuit principle for regulating the power emitted by a sound transducer. A power amplifier is designated by 10, which generates an electrical power required to control a loudspeaker system 20. The current flowing through the loudspeaker system 20 is measured using a measuring resistor 21. The voltage signal at the measuring resistor 21 is fed to a first operational amplifier, designated 30. 33 is a high-pass filter, which is the voltage on the speaker system 20 with the connects inverting input of operational amplifier 30. A second operational amplifier 40 amplifies a difference signal which is formed from the output signal of the operational amplifier 30 and the voltage applied to the loudspeaker system. The output of the operational amplifier 30 and the non-inverting input of the operational amplifier 40 are connected to one another via a third high-pass filter 22. The voltage signal is applied to the inverting input of the operational amplifier 40 via a second high-pass filter 45 and an adder 42. In the feedback branch of the operational amplifier 40 there is a low pass 44 which is superimposed at the summation point 42 on the signal from the high pass 45. The output voltage of the operational amplifier 40 is added in an adder 16 to a low-frequency voltage to be amplified and applied to the input of the power amplifier 10. The entire circuit represents a negative current feedback and operates as follows: The current driving the loudspeaker system 20 generates a voltage drop in the measuring resistor 21, which is amplified by the operational amplifier 30. The amplification factor of the amplifier 30 is selected such that its output voltage in operating states in which there are no mechanical resonances in the loudspeaker system 20 is the same in terms of amount and phase of the voltage on the loudspeaker system. The voltage at the loudspeaker system passes through the second high-pass filter 45 to the inverting input of the amplifier 40, the output voltage of the amplifier 30 via the high-pass filter 22 to the non-inverting input of the amplifier 40. In the normal case, the output signal of the operational amplifier 40 is therefore zero.

Im Resonanzfall schwingt das System mit wesentlich geringerer Leistungsaufnahme, die sich ergebende meßbare elektrische Impedanz der Schwingspule erhöht sich aber - Resonanzüberhöhung beim Parallelschwingkreis. Die das Lautsprechersystem antreibende Spannung bleibt gleich, während der Strom durch das Lautsprechersystem stark abnimmt, d.h. mit anderen Worten, das Eingangssignal des Operationsverstärkers 30 wird kleiner. Infolgedessen liegt jetzt am Operationsverstärker 40 ein Differenzsignal an, das ungleich Null ist. Dieses Signal wird vom Operationsverstärker 40 verstärkt und im Summationspunkt 16 der zu verstärkenden niederfrequenten Spannung überlagert. Bei geeigneter Wahl der Hochpässe 22, 33 und 45 überlagern sich die beiden Signale so, daß die vom Lautsprechersystem abgestrahlte Schalleistung konstant bleibt. Durch die beschriebenen Maßnahmen wird das Impulsverhalten des Lautsprechersystemes ebenfalls verbessert, da die durch Impulse angeregten mechanischen Schwingungen infolge der Gegenkopplung schnell gedämpft werden.In the event of a resonance, the system vibrates with a significantly lower power consumption, but the resulting measurable electrical impedance of the voice coil increases - excessive resonance in the parallel resonant circuit. The voltage driving the speaker system remains the same, while the current through the speaker system decreases sharply, i.e. in other words, the input signal of the operational amplifier 30 becomes smaller. As a result, a differential signal that is not equal to zero is now present at the operational amplifier 40. This signal is amplified by the operational amplifier 40 and superimposed at the summation point 16 of the low-frequency voltage to be amplified. If the high-pass filters 22, 33 and 45 are selected appropriately, the two signals are superimposed so that the sound power emitted by the loudspeaker system remains constant. The measures described also improve the pulse behavior of the loudspeaker system, since the mechanical vibrations excited by pulses are quickly dampened as a result of the negative feedback.

Das in Fig. 2 dargestellte Schaltungsprinzip hat jedoch noch einen weiteren Vorteil. Häufig fehlen bei der Verwendung kostengünstiger Schallwandler die tiefen Frequenzen unterhalb 200 Hz im Wiedergabespektrum. Der Schalldruck läßt bei Frequenzen unterhalb von 200 Hz deutlich nach, wodurch die Wiedergabe grell klingt. Die Impedanz des Lautsprechersystems nimmt bei diesen Frequenzen ebenfalls ab. Wird die untere Grenzfrequenz des Hochpaßfilters 45 höher gewählt als die des Filters 22, so tritt unterhalb der Grenzfrequenz im Korrektursignal eine Phasendrehung von 180° auf, die eine Mitkopplung in diesem Frequenzbereich bewirkt (vgl. Fig. 1c, 5). Durch diese Maßnahme kann das Schallabstrahlungsverhalten des Lautsprechersystemes bei tiefen Frequenzen verbessert werden. Mit Hilfe des Filters 44 läßt sich das Schallabstrahlungsverhalten bei hohen Frequenzen beeinflussen (vgl. Fig. 1c, 6).The circuit principle shown in Fig. 2 has yet another advantage. Frequently, when using inexpensive sound transducers, the low frequencies below 200 Hz are missing in the reproduction spectrum. The sound pressure drops significantly at frequencies below 200 Hz, which makes the reproduction sound garish. The impedance of the speaker system also decreases at these frequencies. If the lower cut-off frequency of the high-pass filter 45 is selected to be higher than that of the filter 22, a phase rotation of 180 ° occurs below the cut-off frequency in the correction signal, which causes positive feedback in this frequency range (cf. FIGS. 1c, 5). This measure can Sound radiation behavior of the speaker system can be improved at low frequencies. With the help of the filter 44, the sound radiation behavior at high frequencies can be influenced (cf. FIGS. 1c, 6).

Fig. 3 zeigt ein Schaltungsbeispiel für das Prinzipschaltbild nach Fig. 2. Gleiche Bezugszeichen bezeichnen die gleichen Elemente wie in Fig. 1. Auf die Darstellung aller Einzelheiten der Schaltung wird hier verzichtet, da der Kern der Erfindung nicht im Aufbau der Schaltung sondern im benutzten Prinzip liegt. Von Bedeutung ist, daß es sich beim Operationsverstärker 30 um einen symmetrisch aufgebauten Verstärker handelt. D.h., daß die Widerstände 35 und der im Hochpaß 33 liegende Widerstand gleich sind, und daß die beiden Widerstände 34 und 36 einander gleich sind.3 shows a circuit example for the basic circuit diagram according to FIG. 2. The same reference numerals designate the same elements as in FIG. 1. All details of the circuit are omitted here, since the essence of the invention is not in the construction of the circuit but in the one used Principle lies. It is important that the operational amplifier 30 is a symmetrically constructed amplifier. That is, the resistors 35 and the high-pass resistor 33 are the same, and the two resistors 34 and 36 are the same.

Claims (13)

1. Verfahren zur Linearisierung des Frequenzganges eines Lautsprechersystems, insbesondere zur Unterdrückung von Resonanzerscheinungen, bei dem einem Eingangssignal eines das Lautsprechersystem ansteuernden Leistungsverstärkers ein Korrektursignal überlagert wird, dadurch gekennzeichnet, daß das Korrektursignal aus der Impedanz des Lautsprechersystems abgeleitet wird.1. A method for linearizing the frequency response of a loudspeaker system, in particular for suppressing resonance phenomena, in which an input signal of a power amplifier controlling the loudspeaker system is overlaid with a correction signal, characterized in that the correction signal is derived from the impedance of the loudspeaker system. 2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß aus einem durch das Lautsprechersystem fließenden Strom ein erstes Signal erzeugt wird.2. The method according to claim 1, characterized in that a first signal is generated from a current flowing through the speaker system. 3. Verfahren nach Anspruch 2, dadurch gekennzeichnet, daß das Korrektursignal durch Filterung aus dem ersten Signal gewonnen wird.3. The method according to claim 2, characterized in that the correction signal is obtained by filtering from the first signal. 4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß als Filter Hoch- und/oder Tiefpaßfilter verwendet werden.4. The method according to claim 3, characterized in that high and / or low pass filters are used as filters. 5 Verfahren nach Anspruch 4, dadurch gekennzeichnet, daß die Filterkoeffizienten der Filter abhängig vom Lautsprechersystem wählbar sind.5 The method according to claim 4, characterized in that the filter coefficients of the filter can be selected depending on the speaker system. 6 Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß Eingangssignal und Korrektursignal additiv überlagert werden.6 The method according to claim 1, characterized in that the input signal and correction signal are additively superimposed. 7. Vorrichtung zur Linearisierung des Frequenzganges eines Lautsprechersystems, insbesondere zur Unterdrückung von Resonanzerscheinungen, mit einem das Lautsprechersystem ansteuerenden Leistungsverstärker, dadurch gekennzeichnet, daß der Leistungsverstärker und das Lautsprechersystem über einen Meßwiderstand miteinander verbunden sind.7. Device for linearizing the frequency response of a loudspeaker system, in particular for suppressing resonance phenomena, with a power amplifier controlling the loudspeaker system, characterized in that the power amplifier and the loudspeaker system are connected to one another via a measuring resistor. 8. Vorrichtung nach Anspruch 7, dadurch gekennzeichnet, daß eine am Meßwiderstand auftretende Spannung Eingangssignal eines ersten Operationsverstärkers ist.8. The device according to claim 7, characterized in that a voltage occurring at the measuring resistor is the input signal of a first operational amplifier. 9. Vorrichtung nach Anspruch 8, dadurch gekennzeichnet, daß ein zweiter Operationsverstärker eine Differenz aus der am Lautsprechersystem liegenden Spannung und der Ausgangsspannung des ersten Operationsverstärkers bildet9. The device according to claim 8, characterized in that a second operational amplifier forms a difference between the voltage on the speaker system and the output voltage of the first operational amplifier 10. Vorrichtung nach Anspruch 8, dadurch gekennzeichnet, daß die am Meßwiderstand auftretende Spannung über einen ersten Hochpaß mit dem invertierenden Eingang des ersten Operationsverstärkers verbunden ist.10. The device according to claim 8, characterized in that the voltage occurring at the measuring resistor is connected via a first high-pass filter to the inverting input of the first operational amplifier. 11. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß der Ausgang des ersten Operationsverstärkers über einen dritten Hochpaß mit dem nicht invertierenden Eingang des zweiten Operationsverstärkers verbunden ist.11. The device according to claim 9, characterized in that the output of the first operational amplifier is connected via a third high-pass filter to the non-inverting input of the second operational amplifier. 12. Vorrichtung nach Anspruch 9, dadurch gekennzeichnet, daß die am Lautsprecher liegende Spannung über einen zweiten Hochpaß auf den invertierenden Eingang des zweiten Operationsverstärkers gegeben wird.12. The apparatus according to claim 9, characterized in that the voltage across the loudspeaker is given via a second high pass to the inverting input of the second operational amplifier. 13. Vorrichtung nach Anspruch 7, dadurch gekennzeichnet, daß der Widerstandswert des Meßwiderstandes um ein bis zwei Zehnerpotenzen kleiner als die Impedanz des Lautsprechersystems ist.13. The apparatus according to claim 7, characterized in that the resistance value of the measuring resistor is one to two powers of ten smaller than the impedance of the speaker system.
EP19890119821 1988-10-28 1989-10-25 Method and device for linearizing the frequency response of a loudspeaker system Ceased EP0366109A3 (en)

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DE3836745 1988-10-28
DE3836745A DE3836745A1 (en) 1988-10-28 1988-10-28 METHOD AND DEVICE FOR LINEARIZING THE FREQUENCY GEAR OF A SPEAKER SYSTEM

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EP0366109A3 (en) 1991-12-11
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