JPH11146482A - Audio system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform correction corresponding to the real reactance characteristics of a speaker. SOLUTION: A reactance characteristic determining part 12 finds the real reactance characteristics of a speaker 15, and an arithmetic part 18 generates an error signal e(n) as the difference of a target response d(n) and a speaker terminal voltage d(n). An adaptive signal processor 11 is provided with an adaptive filter 11a, filter 11b for generating a reference signal r(n) to be used for adaptive signal processing by convolving reactance characteristics C into an audio signal x(n), and adaptive signal processing part 11c for determining the coefficient of the adaptive filter 11a by performing adaptive signal processing so as to minimize the power of the error signal e(n) when the audio signal x(n) is respectively inputted to the adaptive filter 11a and the filter 11b for reference signal generation, and generates an audio signal y(n) to be inputted from the adaptive filter 11a to an amplifier 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio device, and more particularly, to an audio device that emits sound from a speaker to a space by correcting the effect of reactance of a speaker driven by an amplifier output.

[0002]

2. Description of the Related Art There is a load reactance compensator (load induction resistance corrector) as a means for correcting the influence of reactance of a speaker connected to a power amplifier. The reactance increases as the frequency increases, and the characteristics (phase characteristics and gain characteristics) for the input signal differ between the high, middle, and low ranges. Therefore, the load induction resistance compensator adjusts the input signal to the low band (20 Hz to 150 Hz) and the middle band (150 to 250 Hz).
(0 Hz) and high frequency (2500 Hz to 25000 Hz) and analyze them to correct the level of each band, and further correct the phase characteristics of each band in anticipation of the influence of reactance in each band. Specifically, in the phase correction system, the high band is passed without delay, then the middle band is passed through the band-pass filter with a delay of about 0.5 msec, and the low band is passed with the delay and the low-pass filter with a delay of 2.5 msec. And have a time delay characteristic. As described above, the phase correction is performed by preventing the time delay from occurring in the higher frequency range, and the transient distortion of the speaker is minimized. Then
When the high frequency component is less than the middle frequency by the harmonic correction system, the high frequency is emphasized.On the contrary, when the high frequency component is sufficient, the high frequency is weakened. balance)
Lead to.

[0003] Figure 1 is a block diagram illustrating the principal components of an audio device equipped with such a load induced resistance corrector, low frequency, respectively the audio signal S _A 1 to 3, middle band, low-pass filter for separating outputting a high frequency component (LPF), band-pass filter (BPF), high-pass filter (HPF), 4 is a power amplifier, 5 is a speaker driven by a power amplifier output, 6 is a load induction resistor to which each filter output is input and performs the above-described correction control. It is a corrector.

[0004]

The overall reactance characteristics from the power amplifier to the speaker differ depending on the audio system used. That is, if the system changes, the same reactance characteristics are not obtained. What is particularly troublesome is the magnitude of the input signal applied to the speaker,
Depending on the magnitude of the power, the temperature of the voice coil fluctuates,
As a result, the reactance characteristics fluctuate.
Conventionally, the reactance characteristic is roughly corrected using a fixed corrector (BBEIC) without considering such a change in the reactance characteristic. That is, conventionally, the correction is not performed according to the reactance characteristics of the actual audio system, and the correction is not sufficient.
From the above, it is an object of the present invention to perform correction according to the actual reactance characteristics of an audio system, and to be able to hear a sound faithful to an audio signal.

[0005]

According to the present invention, there is provided an audio apparatus which emits sound from a speaker by correcting the influence of the reactance characteristic of a speaker connected to an amplifier. Is input to the amplifier and the adaptive filter, the adaptive signal processing is performed so that the difference between the output voltage of the adaptive filter and the speaker terminal voltage becomes zero, the coefficient of the adaptive filter is determined, and the coefficient is used as the reactance characteristic. Reactance characteristic determination unit, (2) Target response setting unit that outputs target response when audio signal is input after target response characteristics are set, (3) Outputs error signal that is the difference between target response and speaker terminal voltage (4) an audio signal is input, and an error signal output from the operation unit is input, and adaptive signal processing is performed so that the power of the error signal is minimized. And an adaptive signal processing device for generating an audio signal to be input to the amplifier, the adaptive signal processing device comprising: (4-1) an adaptive filter; and (4-2) adaptively convolving the reactance characteristic with the audio signal. A filter for generating a reference signal used for signal processing, and (4-3) adaptive signal processing for minimizing the power of the error signal when the audio signal is input to the adaptive filter and the reference signal generating filter, respectively. And an audio device that has an adaptive signal processing unit that determines the coefficients of the adaptive filter and generates an audio signal to be input to the amplifier from the adaptive filter.

[0006]

FIG. 2 is a block diagram of an audio apparatus according to the present invention. In the figure, reference numeral 11 denotes an adaptive signal processing device that performs adaptive signal processing so that a speaker terminal voltage (speaker input signal) matches a target response signal, 12 denotes a reactance characteristic determining unit that obtains a reactance characteristic from an amplifier to a speaker, and 13 denotes a reactance characteristic determination unit. A DA converter for converting a digital audio signal to analog, 14 is a power amplifier, 15 is a speaker driven by an amplifier output, 16 is an AD converter for converting a speaker terminal voltage to digital, and 17 is an audio signal x (n) input. And a target response setting unit 18 for outputting a target signal d (n) from the speaker terminal voltage (speaker input signal) d ^ (n) and a target signal d (n) output from the target response setting unit 17. This is an operation unit for calculating (n).
The voltage amplified by the amplifier 14 is V _A , the output impedance of the amplifier is Z _A , and the impedance Z _{S of the} speaker 15 is
Then, the speaker terminal voltage V _S is given by the following equation: V _S = Z _S · V _A / (Z _A + Z _S ).

In the adaptive signal processing unit 11, reference numeral 11a denotes an adaptive filter having a FIR digital filter configuration to which an audio signal x (n) is input, and 11b denotes an audio signal x (n).
(n) is a filter that generates a reference signal r (n) to be used for adaptive signal processing by convolving the reactance characteristic C ＾. An audio signal x (n) is input to the adaptive filter 11a and the reference signal generation filter 11b. Error
An adaptive signal processing unit that performs adaptive signal processing so as to minimize the power of the signal e (n) and determines coefficients of the adaptive filter 11a. The adaptive signal processing unit converts the audio signal y (n) input to the amplifier 14 from the adaptive filter 11a. Occur

In the reactance characteristic determining section 12, 1
2a is an adaptive filter having a FIR digital filter configuration to which the audio signal y (n) is input, 12b is a calculating unit for calculating the difference ε between the output voltage of the adaptive filter 12a and the speaker terminal voltage, and 12c is the power of the difference ε. Is an adaptive signal processing unit that performs adaptive signal processing to determine the coefficient of the adaptive filter 12a so as to minimize the coefficient and determines the coefficient as the reactance characteristic. As the target response characteristic H set in the target response setting unit 17, a reactance characteristic to be reproduced is set. For example, assuming that a delay time of about half of the number of taps of the adaptive filter 11a is t, the delay time t has
Flat characteristics (gain 1 characteristics) are set in all audio frequency bands (see FIG. 3). The delay time t is for the adaptive filter 11a to accurately approximate the inverse characteristic of the acoustic system. The target response setting unit 17 having such a target response characteristic corresponds to the delay time t of the FIR digital filter. This can be realized by setting the tap coefficient to be set to 1 and the other tap coefficients to 0.

First, white noise having flat characteristics in all bands is input to the amplifier 14 and the reactance characteristic determination unit 12. The adaptive signal processing unit 12c of the reactance characteristic determining unit 12 performs adaptive signal processing so that the difference ε between the output voltage of the adaptive filter 12a and the speaker terminal voltage becomes zero, and determines the coefficient of the adaptive filter 12a. The coefficient is defined as the initial reactance C ＾ from the amplifier to the speaker.
Is set in the reference signal generation filter 11b of the adaptive signal processing device 11. Thereafter, the reactance characteristic determining unit 12
Receives an audio signal y (n), performs adaptive signal processing so that the difference ε becomes zero, and performs a reactance characteristic C ＾
Is determined, and the reactance characteristic C ＾ is sequentially set in the reference signal generation filter 11b.

The adaptive signal processing device 11 and the target response setting unit 1
7 and the operation unit 18 constitute an adaptive equalization system, and control is performed so that the speaker terminal voltage d ＾ (n) matches the target response d (n) set in the target response setting unit 17. That is, the adaptive signal processing unit 11c receives the error signal e (n) and the adaptive signal processing reference signal r input through the filter 11b.
(n) is input, and adaptive signal processing is performed using these signals so that the speaker terminal voltage signal d ^ (n) becomes equal to the target signal d (n) to determine the coefficients of the adaptive filter 11a.
For example, the adaptive signal processing unit 11c uses a well-known LMS (Least M
ean Square) error signal e according to the adaptive algorithm
The coefficient of the adaptive filter 11a is determined so that the power of (n) becomes minimum. The adaptive filter 11a outputs the audio signal x according to the coefficient determined by the adaptive signal processing unit 11c.
(n) is subjected to digital filter processing to output a signal y (n). Therefore, if the coefficients of the adaptive filter 11a converge so that the power of the error signal e (n) is minimized by the adaptive signal processing, the speaker terminal voltage signal d ^ (n) becomes the target signal d
(n). This means that an ideal audio signal having a flat frequency characteristic set in the target response setting unit 17 and having no phase delay is input to the speaker terminal, and a sound whose reactance characteristic has been corrected is output from the speaker 15. Is done. As described above, the present invention has been described with reference to the embodiments. However, the present invention can be variously modified in accordance with the gist of the present invention described in the claims, and the present invention does not exclude these.

[0011]

As described above, according to the present invention, (1) an actual reactance characteristic from an amplifier to a speaker is obtained, and (2) a reference signal used for adaptive signal processing is generated by convolving the reactance characteristic with an audio signal. (3) generate an error signal that is the difference between the target response and the speaker terminal voltage; (4) receive the reference signal and the error signal and perform adaptive signal processing so that the power of the error signal is minimized. (5) Since the adaptive filter generates the audio signal to be input to the amplifier from the adaptive filter, correction can be made according to the actual reactance characteristics of the audio system, and a sound faithful to the audio signal can be obtained. Can be heard.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of an audio device including a load induction resistance corrector.

FIG. 2 is a configuration diagram of an audio device of the present invention.

FIG. 3 is an explanatory diagram of characteristics set in a target response setting unit.

[Explanation of symbols]

 11. Adaptive signal processing device 11a Adaptive filter 11b Reactance characteristic C ＾ Convolution filter 11c Adaptive signal processing unit 12 Reactance characteristic determination unit 12a Adaptive filter 12b Arithmetic unit 12c Adaptive signal processing unit 14. Power amplifier 15. Speaker 17. Target response setting unit 18. Operation unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04R 3/04 102 H04R 3/04 102

Claims (1)

[Claims] An audio device that emits sound from a speaker by correcting the influence of the reactance characteristic of a speaker driven by an amplifier output. When a signal is input to an amplifier and an adaptive filter, the output voltage of the adaptive filter and the speaker A reactance characteristic determination unit that performs adaptive signal processing to determine a coefficient of the adaptive filter so that a difference from the terminal voltage becomes zero, sets the coefficient as the reactance characteristic, sets a target response characteristic, and receives an audio signal. A target response setting unit for outputting a target response, a calculation unit for outputting an error signal representing a difference between the target response and the speaker terminal voltage, and an error signal output from the calculation unit while receiving an audio signal. An adaptive audio signal processing is performed so that the power of the error signal is minimized, and the audio signal input to the amplifier is The adaptive signal processing device comprises: an adaptive filter; a filter configured to convolve the reactance characteristic with an audio signal to generate a reference signal used for adaptive signal processing; An adaptive signal processing unit for performing adaptive signal processing to determine the coefficient of the adaptive filter so that the power of the error signal is minimized when the signal is input to the signal generating filter; An audio device for generating an audio signal.