JP2009027631A - Bi-amp correction device and AV amplifier equipped with the same - Google Patents

Abstract

By adding a simple switching circuit and a delay circuit to a multi-channel AV amplifier, high sound quality driving optimization for bi-amp playback is realized at low cost during 2-channel stereo playback.
A switching circuit constituted by simple switches S1 to S18 and delay circuits 3a and 3b are added to an AV amplifier body, and a speaker system is corrected by diverting an automatic sound field correcting microphone system. As a result, the multi-channel playback amplifier can be effectively used during 2-channel stereo playback to improve the sound quality during 2-channel stereo playback.
[Selection] Figure 1

Description

  The present invention relates to a bi-amplifier correction device useful for an audio device such as an AV amplifier or a receiver that can perform multi-channel playback and 2-channel stereo playback. The present invention also relates to an AV amplifier provided with a biamplifier correction device.

  Conventionally, a Dolby surround system is known as a surround system as a multi-channel AV amplifier. The Dolby surround system is configured with three channels on the front side and one channel on the rear side. The surround processor circuit uses left and right two-channel stereo audio signals L and R to input left and right audio FL and FR (stereo) for front speakers and left and right audio RL and RR (mono) for rear speakers by internal logic. ), And generates and outputs five voices synthesized from the voice C for the center speaker. The five audio signals are amplified by a power amplifier provided for each output circuit and then sent to each speaker through a speaker terminal, and audio is output from each speaker. Accordingly, Dolby surround reproduction can be performed from the input 2-channel stereo audio signal.

FIG. 5 shows another configuration example of a conventional AV amplifier. The Lch audio signal input to the input terminal 101a and the Rch audio signal input to the input terminal 101b are input to the prologic decoding unit 102. The prologic decoding unit 102 generates 4ch audio signals of Lch, Rch, Cch, and Sch by signal processing based on the input 2ch audio signal. The Lch audio signal is amplified by the amplifier 103 a and input to the high frequency input terminal HF and the low frequency input terminal LF of the Lch speaker 104. The Rch audio signal is amplified by the amplifier 103c and input to the high frequency input terminal HF and the low frequency input terminal LF of the Rch speaker 105. The Cch audio signal is amplified by the amplifier 103 b and input to the Cch speaker 106. The Sch audio signal is amplified by the amplifier 103 d and input to the Sch speaker 107. As a result, sound corresponding to surround reproduction is output from each speaker.
JP 10-313223 A

  However, in the case of the conventional configuration as described above, since only the amplifiers 103a and 103c are operated at the time of two-channel stereo reproduction, the amplifiers 103b and 103d have a problem that they cannot contribute to improvement of sound quality at the time of two-channel reproduction. .

  An object of the present invention is to realize high sound quality drive optimization for bi-amp reproduction at a low cost by adding a simple switching circuit and delay circuit to a multi-channel AV amplifier.

  The AV amplifier according to the present invention is an AV amplifier capable of selectively switching between a multi-channel playback mode and a 2-channel stereo playback mode, and is capable of correcting the signal level of the first signal source. Gain correction means, first delay means capable of delaying the signal corrected by the first gain correction means, and a signal delayed by the first delay means for amplifying the high frequency terminal of the first speaker The first amplifying means for outputting to the first amplifier, the second amplifying means for amplifying the signal corrected by the second gain correcting means and outputting the amplified signal to the low frequency terminal of the first speaker, and the multi-channel playback mode. Amplifies the signal from the first signal source by the first amplifying means and outputs the amplified signal to the high and low frequency terminals of the first speaker, and the signal from the second signal source to the second signal source Amplifying means for amplifying the second speaker high and low When the two-channel stereo reproduction is output to the terminal, the signal of the first signal source is amplified by the first amplification means via the first gain correction means and the first delay means, and While outputting to the high frequency terminal of a 1st speaker, the signal of the said 1st signal source is amplified by the said 2nd amplification means via the said 2nd gain correction means, and the low frequency of the said 1st speaker A switch for switching to output to the terminal, the first and second gain correction means, the first delay means, and a control means for controlling the operation of the switch, and the first speaker or the second speaker. Detecting means for detecting a signal output from a high-frequency terminal or a low-frequency terminal of the first loudspeaker, wherein the control means is based on the signal detected by the detecting means, and the first high-frequency terminal of the first speaker The first played The gain correction means corrects the level so that the power level and the second output level reproduced from the second low-frequency terminal of the first speaker are equal to each other at the listening position, and from the generation of the input signal The delay amount in the first delay means is corrected so that the time until the output signal reproduction becomes equal.

  Thus, the present invention enables further two-channel stereo high-quality sound reproduction by optimally correcting the level and phase during bi-amp reproduction.

  According to the present invention, the optimization of bi-amp switching at the time of two-channel stereo playback can be realized with a simple configuration and an AV amplifier for multi-channel playback in a popular price range. There is an advantage that the significant sound quality improvement that has been achieved can be realized at a low cost when reproducing two-channel stereo.

  The present invention may further include a test signal transmission unit that transmits a test signal and a microphone circuit that collects sound reproduced and output from a speaker. With this configuration, it is possible to improve the sound quality during 2-channel stereo playback with a simple configuration.

(Embodiment)
[1. Configuration and playback operation of AV amplifier]
FIG. 1 is a block diagram of a biamplifier correction apparatus according to an embodiment. In FIG. 1, input terminals 1a to 1d are terminals to which audio signals decoded by Dolby Surround are input. An Lch audio signal is input to the input terminal 1a, an Rch audio signal is input to the input terminal 1b, a Cch audio signal is input to the input terminal 1c, and an Sch audio signal is input to the input terminal 1d. Entered.

  The gain correction circuits 2a to 2d correct the gain of the input audio signal under the control of the CPU 11. The gain correction circuit 2a is connected to the input terminal 1a via the switch S15 and corrects the gain of the Lch audio signal. The gain correction circuit 2b corrects the gain of the test signal input via the switch S17. The gain correction circuit 2c is connected to the input terminal 1b via the switch S16 and corrects the gain of the Rch audio signal. The gain correction circuit 2d corrects the gain of the test signal input via the switch S18. The gain correction circuits 2a and 2c are examples of first gain correction means. The gain correction circuits 2b and 2d are an example of second gain correction means.

  The delay circuit 3a delays the phase of the audio signal output from the gain correction circuit 2a under the control of the CPU 11. The delay circuit 3b delays the phase of the audio signal output from the gain correction circuit 2c under the control of the CPU 11. The delay circuits 3a and 3b are an example of delay means.

  The amplifier 4a has an input connected to the switches S11 and S12. Further, the output is connected to a high frequency terminal (hereinafter referred to as HF terminal) of the Lch speaker 5 and is also connected to a low frequency terminal (hereinafter referred to as LF terminal) of the Lch speaker 5 via the switch S1. . The input of the amplifier 4b is connected to the switches S5 and S2. Further, the output is connected to the LF terminal of the Lch speaker 5 through the switch S3 and is connected to the Cch speaker 7 through the switch S4. The input of the amplifier 4c is connected to the switches S13 and S14. The output is connected to the HF terminal of the Rch speaker 6 and is connected to the LF terminal of the Rch speaker 6 via the switch S6. The amplifier 4d has an input connected to the switches S10 and S7. Further, the output is connected to the LF terminal of the Rch speaker 6 through the switch S8 and is connected to the Sch speaker 8 through the switch S9. The amplifiers 4a and 4c are an example of first amplification means. The amplifiers 4b and 4d are an example of second amplification means.

  The Lch speaker 5 (first speaker) and the Rch speaker 6 (second speaker) are generally arranged on the front left and right with respect to the listening position of the listener. Further, the Cch speaker 7 (center speaker) is arranged at the front center with respect to the listening position. In addition, the Sch speaker 8 (surround speaker) is disposed behind the listening position.

  The test signal generator 9 generates a test signal when measuring and adjusting the level and delay time of each speaker. In this embodiment, a continuous sine wave (pure sound) signal is output when the speaker level is measured, and an impulse sound (instant sound) signal is output when the delay time of the speaker is measured.

  The microphone 10 is arranged at a listening position when testing a speaker, and collects sound output from each speaker. The collected voice is transmitted to the CPU 11 as a voice signal. The microphone 10 is an example of a detection unit.

  The CPU 11 analyzes the audio signal output from the microphone 10 and controls the operations of the gain correction circuits 2a to 2d and the delay circuits 3a and 3b. Further, the CPU 11 controls the on / off switching of the switches S1 to S18 when the key operation unit 12 is operated by the user. Specific operation control of each part will be described later.

  The switches S1 to S18 that are the first to eighteenth switches are constituted by interlocking switches, and are configured to be simultaneously turned on or off under the control of the CPU 11.

  The key operation unit 12 can select a 2-channel stereo playback mode or a 4-channel playback mode. The key operation unit 12 is provided on the operation panel of the AV amplifier or is operated by the user by a remote control input signal.

  The ROM 13 stores an operation program for the CPU 11. The CPU 101 operates according to this operation program.

  The RAM 14 functions as a working memory that stores various work data generated when the CPU 11 performs a program operation. Note that the CPU 11, or the CPU 11, the ROM 13, and the RAM 14 are examples of control means.

  The operation of the biamplifier correction circuit configured as described above will be described below.

  First, an operation when the AV amplifier according to the present embodiment is used as a multi-channel compatible AV amplifier that is generally used as a home theater playback device will be described.

  When the user operates the key operation unit 12 to select “multi-channel playback”, which is a function of the AV amplifier, and plays a recording medium on which multi-channel encoded audio such as a movie is recorded, Are separated into four signals Lch, Rch, Cch, and Sch, and input to the input terminals 1a to 1d, respectively. At this time, the CPU 11 switches each switch as shown in (Table 1).

  That is, during multi-channel playback, the switches S1, S2, S4, S6, S7, S9, S11, S13, S15, S16 are turned on, and the switches S3, S5, S8, S10, S12, S14, S17, S18 are turned off. Control to

  The Lch audio signal input to the input terminal 1a is input to the amplifier 4a and amplified because the switches S15 and S11 are closed and the switches S5, S12, and S17 are open. The audio signal output from the amplifier 4a is applied to the HF terminal and the LF terminal of the Lch speaker 5 because the switch S1 is closed and the switch S3 is open. The Lch speaker 5 reproduces and outputs sound based on the input sound signal in the normal mode.

  The Rch audio signal input to the input terminal 1b is input to the amplifier 4c and amplified because the switches S16 and S13 are closed and the switches S10, S14, and S18 are open. The audio signal output from the amplifier 4c is applied to the HF terminal and the LF terminal of the Rch speaker 6 because the switch S6 is closed and the switch S8 is open. The Rch speaker 6 reproduces and outputs sound based on the input sound signal in the normal mode.

  The Cch audio signal input to the input terminal 1c is input to the amplifier 4b and amplified because the switch S2 is closed. The audio signal output from the amplifier 4b is input to the Cch speaker 7 because the switch S3 is open and the switch S4 is closed. The Cch speaker 7 reproduces and outputs sound based on the input sound signal.

  Also, the Sch audio signal input to the input terminal 1d is input to the amplifier 4d and amplified because the switch S7 is closed. The audio signal output from the amplifier 4d is input to the Sch speaker 8 because the switch S8 is open and the switch S9 is closed. The Sch speaker 8 reproduces and outputs sound based on the input sound signal.

  Note that the delay circuits 3a and 3b are not operating because the switches S5, S10, S12, and S14 are open.

  Next, the operation in the case of normal stereo reproduction (2ch) will be described.

  The 2ch stereo sound is composed of only the Lch sound signal and the Rch sound signal. When the user operates the key operation unit 12 and “2-channel stereo reproduction” is selected from the functions of the AV amplifier, the CPU 11 switches S3, S5, S8, and S10 as shown in (Table 1). , S12, S14, S15, S16 are closed, and the switches S1, S2, S4, S6, S7, S9, S11, S13, S17, S18 are controlled to be opened.

  Thereby, since the switches S15 and S12 are closed and the switch S11 is open, the Lch audio signal input to the input terminal 1a passes through the switch S15, the gain correction circuit 2a, the delay circuit 3a, and the switch S12, and is amplified. 4a is input and amplified. The audio signal output from the amplifier 4a is input to the HF terminal of the Lch speaker 5 because the switch S1 is open. Further, since the switch S5 is closed, the Lch audio signal input to the input terminal 1a is input to the amplifier 4b and amplified through the switch S15, the gain correction circuit 2b, and the switch S5. The audio signal output from the amplifier 4b is input to the LF terminal of the Lch speaker 5 through the switch S3 because the switch S3 is closed and the switch S4 is open. As a result, the Lch speaker 5 reproduces the sound based on the input sound signal by bi-amplification.

  On the other hand, the Rch audio signal input to the input terminal 1b passes through the switch S16, the gain correction circuit 2c, the delay circuit 3b, and the switch S14 because the switches S16 and S14 are closed and the switch S13 is open. To be amplified. The audio signal output from the amplifier 4c is input to the HF terminal of the Rch speaker 6 because the switch S6 is open. The Rch audio signal input to the input terminal 1b is input to the amplifier 4d and amplified through the switch S16, the gain correction circuit 2d, and the switch S10 because the switch S10 is closed. The audio signal output from the amplifier 4d is input to the LF terminal of the Rch speaker 6 through the switch S8 because the switch S8 is closed and the switch S9 is open. As a result, the Rch speaker 6 reproduces the sound based on the input sound signal by bi-amplification.

  Bi-amp playback is a playback where the input audio signal is divided into high and low frequencies, passed through an amplifier, the audio signals are input independently to the low and high frequency speakers, and the audio is played back on each speaker. It is a method. By playing in this way, it is possible to prevent noise components generated due to excessive vibration in the diaphragm of the low-frequency speaker from flowing into the high-frequency side, and to produce high-quality sound with high sound purity Can be played.

[2. (Speaker test operation)
As shown in FIG. 2, the high-frequency speaker 22 and the low-frequency speaker 23 fixed to the speaker box 21 have their diaphragm structures until the sound actually output from each speaker reaches the listening position. There are differences in time and level. Usually, since the diaphragm of the high frequency speaker 22 is small, the time t1 from when the sound is output until reaching the listening position is shorter than the arrival time t2 of the low frequency speaker 23. Further, the level of the output audio varies between the high frequency speaker 22 and the low frequency speaker 23. The AV amplifier according to the present embodiment has a function of correcting such time difference and level difference between the high frequency speaker 22 and the low frequency speaker 23. Hereinafter, the correction operation will be described.

  When the user operates the key operation unit 12 and “speaker test” is selected from the functions of the AV amplifier, the CPU 11 switches S3, S5, S8, S10, and S12 as shown in (Table 1). , S14, S17, and S18 are closed, and switches S1, S2, S4, S6, S7, S9, S11, S13, S15, and S16 are opened. As a result, the test signal output from the test signal generator 9 can be input to the HF terminal of the Lch speaker 5 via the switch S17, the level correction circuit 2a, the delay circuit 3a, the switch S12, and the amplifier 4a. Then, the signal can be input to the LF terminal of the Lch speaker 5 through the level correction circuit 2b, the switch S5, the amplifier 4b, and the switch S3. The test signal output from the test signal generator 9 can be input to the HF terminal of the Rch speaker 6 via the switch S18, the level correction circuit 2c, the delay circuit 3b, the switch S14, and the amplifier 4c. The signal can be input to the LF terminal of the Rch speaker 6 via the level correction circuit 2d, the switch S10, the amplifier 4d, and the switch S8. In this state, the speaker test can be started.

[2-1. (Level correction)
FIG. 3 shows a method for speaker level measurement and correction. In the present embodiment, level measurement is performed in the order of the high frequency speaker of the Lch speaker 5, the low frequency speaker, the high frequency speaker of the Rch speaker 6, and the low frequency speaker.

  When the speaker test is started, the test signal generator 9 outputs a continuous pure sine wave as a test signal for level measurement (S101).

  In order to measure the level of the high frequency speaker of the Lch speaker 5, each switch is temporarily opened from the state shown in (Table 1), and the test signal is input only to the HF terminal of the Lch speaker 5. Like that. The test signal output from the test signal generator 9 is input to the HF terminal of the Lch speaker 5, and sound is output from the high frequency speaker. The sound output from the Lch speaker 5 is picked up by the microphone 10 disposed at the listening position. The sound collected by the microphone 10 is sent to the CPU 11 as an audio signal. The CPU 11 measures the level of the input high frequency audio signal (S102).

  Next, in order to measure the level of the low frequency speaker of the Lch speaker 5, each switch is temporarily opened from the state shown in (Table 1), and the test signal is applied only to the LF terminal of the Lch speaker 5. To be entered. The test signal output from the test signal generator 9 is input to the LF terminal of the Lch speaker 5, and sound is output from the low frequency speaker. The sound output from the Lch speaker 5 is picked up by the microphone 10 disposed at the listening position. The sound collected by the microphone 10 is sent to the CPU 11 as an audio signal. The CPU 11 measures the level of the input low frequency audio signal (S103).

  Next, the CPU 11 calculates a level difference between the high frequency sound signal and the low frequency sound signal based on the automatic sound field correction algorithm programmed in the ROM 13 and the RAM 103 (S104).

  Next, the CPU 11 calculates a correction amount so that the level of the high frequency audio signal and the level of the low frequency audio signal are equal, and controls the gain correction circuits 2a and 2b to increase the gain of the audio signal. to correct. Here, when the gain of the high frequency audio signal is corrected to match the level of the low frequency audio signal, the correction amount of the gain correction circuit 2a is controlled. When the gain of the low frequency audio signal is corrected to match the level of the high frequency audio signal, the correction amount of the gain correction circuit 2b is controlled (S105).

  Thus, the level correction of the Lch speaker 5 is completed.

  Next, when performing level correction of the Rch speaker 6, the switch S17 is temporarily opened and the switch S18 is temporarily closed. As a result, the test signal output from the test signal generator 9 is output only to the Rch speaker 6 side. A specific correction method is the same as the correction method of the Lch speaker 5 described above with reference to FIG.

  In this embodiment, the level of the Lch speaker 5 is corrected and then the Rch speaker 6 is corrected. However, the correction may be made in the reverse order.

  In the present embodiment, the level measurement of the low-frequency speaker is performed after the level measurement of the high-frequency speaker is performed. However, the configuration may be such that the measurement is performed in the reverse order.

  In the present embodiment, the test signal is composed of a continuous pure sound of a sine wave. However, other test signals may be used as long as at least the level of the speaker can be measured.

  Further, the test signal generated by the test signal generator 9 may be one type (one frequency), or a plurality of types of test signals of different frequencies are sequentially output, and the speaker level is determined for each type of test signal. It is good also as a structure which performs a measurement.

[2-2. (Delay time correction)
FIG. 4 shows a method for measuring and correcting the delay time of the speaker. In the present embodiment, the delay time measurement is performed in the order of the high frequency speaker of the Lch speaker 5, the low frequency speaker, the high frequency speaker of the Rch speaker 6, and the low frequency speaker.

  When the speaker test is started, the test signal generator 9 outputs an impulse signal (instantaneous sound generation) as a delay time measurement test signal (S201).

  In order to measure the delay time of the high frequency speaker of the Lch speaker 5, each switch is temporarily opened from the state shown in (Table 1), and the test signal is input only to the HF terminal of the Lch speaker 5. So that The test signal output from the test signal generator 9 is input to the HF terminal of the Lch speaker 5, and sound is output from the high frequency speaker. The sound output from the Lch speaker 5 is picked up by the microphone 10 disposed at the listening position. The sound collected by the microphone 10 is sent to the CPU 11 as an audio signal. The CPU 11 measures the delay time of the input high frequency audio signal. Specifically, the time from when the test signal is output from the test signal generator 9 until the microphone 10 picks up the sound output from the high frequency speaker is measured (S202).

  Next, in order to measure the delay time of the low frequency speaker of the Lch speaker 5, each switch is temporarily opened from the state shown in (Table 1), and the test signal is only for the LF terminal of the Lch speaker 5. To be entered. The test signal output from the test signal generator 9 is input to the LF terminal of the Lch speaker 5, and sound is output from the low frequency speaker. The sound output from the Lch speaker 5 is picked up by the microphone 10 disposed at the listening position. The sound collected by the microphone 10 is sent to the CPU 11 as an audio signal. The CPU 11 measures the delay time of the input low frequency audio signal. Specifically, the time from when the test signal is output from the test signal generator 9 until the microphone 10 picks up the sound output from the low-frequency speaker is measured (S203).

  Next, the CPU 11 calculates the difference in delay time between the high frequency sound signal and the low frequency sound signal based on the automatic sound field correction algorithm programmed in the ROM 13 and the RAM 103 (S204).

  Next, the CPU 11 calculates a correction amount so that the level of the high frequency audio signal and the level of the low frequency audio signal are equal, and controls the delay circuit 2a to control the phase of the high frequency audio signal. Is delayed (S205).

  Here, since the arrival time of the sound from the sounding position to the listening position is shorter (reaches faster) in the high frequency audio signal than in the low frequency audio signal, the phase of the high frequency audio signal is delayed. The arrival time of the high frequency audio signal and the arrival time of the low frequency audio signal can be matched. In order to match the arrival times of the two, it is necessary to set the delay time (delay amount) of the high frequency audio signal so that the difference between the delay times calculated in S204 becomes zero.

  Thus, the correction of the delay time of the Lch speaker 5 is completed.

  Next, when correcting the delay time of the Rch speaker 6, the switch S17 is temporarily opened and the switch S18 is temporarily closed. As a result, the test signal output from the test signal generator 9 is output only to the Rch speaker 6 side. A specific correction method is the same as the correction method of the Lch speaker 5 described above with reference to FIG.

  In this embodiment, the delay time of the Lch speaker 5 is corrected and then the Rch speaker 6 is corrected. However, the correction may be performed in the reverse order.

  In the present embodiment, the delay time of the high-frequency speaker is measured and then the delay time of the low-frequency speaker is measured. However, the measurement may be performed in the reverse order.

  In the present embodiment, the test signal is an impulse signal. However, the test signal may be in another form as long as at least the speaker level can be measured.

  Further, the test signal generated by the test signal generator 9 may be one type (one frequency), or a plurality of types of test signals of different frequencies are sequentially output, and the delay of the speaker for each type of test signal. It is good also as a structure which performs time measurement.

  Here, the automatic sound field correction circuit included in the CPU 11 is a level, distance, or frequency of a normal speaker connected to the AV amplifier using an impulse signal or a sine wave signal mounted in the multi-channel AV amplifier. This function optimizes the characteristics using microphone measurement. In this case, it is possible to automatically optimize the gain and phase of the HF amplifier and the LF amplifier, which have been corrected in the conventional sense of hearing, and expect further effects in improving sound quality.

[3. Effects of the embodiment, etc.]
According to the present embodiment, a switching circuit and a delay circuit configured by simple switches are added to the AV amplifier main body, and the speaker correction is performed by using the automatic sound field correcting microphone system. Therefore, it is possible to effectively improve the sound quality at the time of 2-channel stereo reproduction by effectively using the amplifier for multi-channel reproduction at the time of 2-channel stereo reproduction.

  In the above description, a switch that is turned on or off is used as the switching unit. However, the number of switches can be reduced and the circuit scale can be reduced by using a switch (transfer type) that switches to either one. Effects such as reduction and cost reduction can be obtained.

  In this embodiment, the delay time is corrected after the speaker level is corrected. However, the correction may be performed in reverse order.

  The bi-amplifier correction circuit of the present invention can also be applied to sound quality improvement applications in audio devices such as AV amplifiers and receivers capable of multi-channel playback and 2-channel stereo playback.

Block diagram of AV amplifier in embodiment Schematic diagram for explaining the difference in arrival time of sound from speakers Flow chart showing the procedure of speaker level correction Flow chart showing the procedure for correcting the delay time of the speaker Block diagram of a conventional AV amplifier

Explanation of symbols

2a, 2b, 2c, 2d Gain correction circuit 3a, 3b Delay circuit 4a, 4b, 4c, 4d Amplifier 5 Lch speaker 6 Rch speaker 7 Cch speaker 8 Sch speaker 9 Test signal generator 10 Microphone 11 CPU (Central processing unit)

Claims (2)

An AV amplifier capable of selectively switching between a multi-channel playback mode and a 2-channel stereo playback mode,
First and second gain correction means capable of correcting the signal level of the first signal source;
Delay means capable of delaying the signal corrected by the first gain correction means;
A first amplifying means for amplifying the signal delayed by the delay means and outputting the amplified signal to a high-frequency terminal of the first speaker;
Second amplification means for amplifying the signal corrected by the second gain correction means and outputting the amplified signal to the low-frequency terminal of the first speaker;
In the multi-channel playback mode, the signal from the first signal source is amplified by the first amplifying means and output to the high frequency and low frequency terminals of the first speaker, and the second signal source The signal is amplified by the second amplifying means and output to the high frequency and low frequency terminals of the second speaker, and the signal from the first signal source is used as the first gain during two-channel stereo reproduction. The signal is amplified by the first amplifying means via the correcting means and the delay means and output to the high frequency terminal of the first speaker, and the signal from the first signal source is supplied to the second gain correcting means. A switch for switching to amplify by the second amplification means and output to the low-frequency terminal of the first speaker via
Control means for controlling the operation of the first and second gain correction means, the delay means, and the switch;
Detecting means for detecting a signal output from a high frequency terminal or a low frequency terminal of the first speaker or the second speaker;
The control means includes
Based on the signal detected by the detecting means, the first output level reproduced from the first high frequency terminal of the first speaker and the second output level reproduced from the second low frequency terminal of the first speaker. The gain correction means corrects the level so that the level at the trial listening position is equal to the output level of 2, and
An AV amplifier that corrects the delay amount in the delay means so that the time from generation of an input signal to reproduction of an output signal becomes equal. A test signal transmitter for transmitting a test signal;
The AV amplifier according to claim 1, further comprising a microphone circuit that collects sound reproduced and output from the speaker.

Images