JP2740584B2 - Group delay characteristic correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing apparatus for improving the characteristics and sound quality of a speaker system.

[0002]

2. Description of the Related Art As shown in FIG. 4, a speaker system is known to have a group delay characteristic which becomes maximum at the lowest resonance frequency. However, when a speaker is considered as an ideal electroacoustic transducer, it is desirable that the amplitude characteristic is constant regardless of the frequency, and the group delay characteristic is also constant regardless of the frequency.

Conventionally, the group delay characteristic of a speaker has been corrected,
As means for keeping the frequency constant regardless of the frequency, there is a configuration shown in FIG. In the figure, reference numeral 21 denotes a first FIR filter, 22 denotes a second FIR filter, and 23 denotes a first FIR filter.
The amplitude characteristic of the R filter, 24 is the group delay characteristic of the first FIR filter, 25 is the amplitude characteristic of the second FIR filter,
26 the group delay characteristics of the second FIR filter, the 1 9 FI
The amplitude characteristic of a filter in which an R filter 21 and an FIR filter 22 are connected in cascade, 20 is an FIR filter 21
Group delay characteristics of a filter in which filters 22 are cascaded,
That is, it is a correction amount for the group delay characteristic of the speaker .

Next, the operation will be described. First FIR
The filter 21 has a group delay characteristic 24 for correcting the group delay characteristic 2 of the speaker system. That is, the group delay characteristic of the speaker system becomes constant regardless of the frequency by passing through the first FIR filter 21. However, in the case of the FIR filter, in general, when the design is performed with a characteristic other than the characteristic of the phase straight line (the characteristic with a constant group delay), it is not guaranteed that the amplitude characteristic is constant regardless of the frequency. Therefore, the amplitude characteristics of the first filter 21 are disturbed.

Therefore, the second FIR filter 22 cascades the second FIR filter 21 so that the disturbance of the amplitude characteristic caused by the first FIR filter 21 is corrected by the second FIR filter 22.
FIR filter 22 is connected. The amplitude characteristic 25 of the second FIR filter 22 has a characteristic that cancels out the amplitude characteristic disturbed by the first FIR filter 21. However,
The group delay characteristic of the second FIR filter 22 is constant irrespective of the frequency, and the corrected group delay characteristic remains in the corrected state. That is, the first FIR filter 21
And the second FIR filter 22 are cascaded to form an all-bandpass filter having a group delay characteristic for correcting the group delay characteristic of the speaker.

[0006] The all-bandpass filter having the above-described structure enables control to keep the group delay characteristic constant regardless of the frequency without changing the amplitude characteristic of the speaker system.

[0007]

In the conventional system, since the filter is configured by the FIR filter, there is a problem that the scale of the hardware of the system or the number of steps of the software is increased. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a group delay characteristic correction device that can reproduce characteristics equivalent to those of the related art in a small-scale system.

[0008]

A group delay characteristic according to the present invention.
The compensator converts multiple digital audio data signals.
Of dividing the band has a first IIR type digital filter and the second IIR type digital filter, further,
A delay device for delaying by to the output signal of the first IIR type digital filter, and a phase inverter for inverting 180 ° the phase of the output signal of the second IIR type digital filter, the output of the phase inverter of the N-number of all-pass IIR digital filter for phase adjustment, and an adder for adding the output of the output signal and the previous SL delayer of the total <br/> pass IIR digital filter, the adder and N cascaded graphic equalizer for performing amplitude correction of the output signal, which is constituted by. Also, two all-pass IIR digital filters are connected in cascade, and one graphic equalizer is used.

[0009]

In the present invention, since the filter is constituted by an IIR digital filter, the scale of hardware or software can be made smaller than that realized by using an FIR digital filter. .

[0010]

[Embodiment 1] Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, 1 is the amplitude characteristic of the reproduced signal , 3 is an IIR high-pass filter, 4 is a delay device, 5 is an IIR low-pass filter, 6 is a phase inverter, and 7 is an IIR all-pass filter. filter, the second all-pass filter 8, 9 an adder, 10 a graphic equalizer, 11 is <br/> the amplitude characteristics of the signal after passing through all filters.

FIG. 2 shows the amplitude characteristic of each part of the filter. In the figure, 13 is the amplitude characteristic of the high-frequency signal after passing through the delay unit 4, 14 is the low-frequency amplitude characteristic after passing through the all-pass filter, 15 is the amplitude characteristic of the addition result of the adder 9, 11
Is the amplitude characteristic of the signal after passing through all the filters.

FIG. 3 shows a group delay characteristic of each part of the filter.
In the figure, 16 is the group delay characteristic of the high band signal after passing through the delay unit 4, 17 is the group delay characteristic of the high band after passing through the all-pass filter, 18 is the group delay characteristic of the addition result of the adder 9, 12
Is the group delay characteristic of the signal after passing through all the filters.

Next, the operation will be described. The signal to be reproduced by the speaker is divided into a low band and a high band by a high-pass filter 3 and a low-pass filter 5. The signal that has passed through the high-pass filter 3 is delayed by the delay unit 4. On the other hand, the phase of the signal passing through the low-pass filter 5 is inverted by 180 degrees by the phase inverter 6.

The phase of the low-pass signal whose phase has been inverted is adjusted by the first all-pass filter 7 and the second all-pass filter in preparation for adding the high-pass signal by the adder 9.

The high-frequency signal delayed by the delay unit 4 and the low-frequency signal subjected to the phase adjustment are added by an adder 9. Adder 9
Is added to the graphic equalizer 10
Is used to adjust the amplitude signal.

Each operation state will be described with reference to FIGS. FIG. 2 is a diagram showing the amplitude characteristics of each part. When the high-frequency amplitude characteristic 13 before addition and the low-frequency amplitude characteristic 14 before addition are added, an amplitude signal 15 after addition is obtained. However, since the amplitude signal 15 has a dip, the amplitude is adjusted using the graphic equalizer 10.

FIG. 3 is a diagram showing the group delay characteristic of each section. When the high-frequency group delay signal 16 before the addition and the low-frequency group delay characteristic 17 before the addition are added, A group delay signal 18 having the amplitude characteristic of Also, the insertion of the graphic equalizer for amplitude adjustment results in a final group delay characteristic of 12.

Embodiment 2 FIG. In the first embodiment, a single graphic equalizer is used. However, when a plurality of graphic equalizers are used, the same result as in the first embodiment is obtained.

Embodiment 3 FIG. In the first embodiment, the number of all bandpass filters for the low band signal is two, but here, when the number is increased more than two, the same result as in the first embodiment is obtained.

Embodiment 4 FIG. Embodiment 2 and Embodiment 3 may be combined to increase the number of graphic equalizers and the number of all-band-pass filters for low-frequency signals from two.

[0021]

Since the present invention is configured as described above, it does not change the amplitude reproduction characteristics of the speaker.
A group delay in a low band is corrected, and a constant group delay characteristic is realized regardless of a frequency. By realizing a constant group delay characteristic irrespective of the frequency, the low-frequency reproduction characteristic is improved. Further, since the filter is configured by an IIR type digital filter, it is possible to reproduce the same characteristics with a system having a smaller scale than that of the FIR type digital filter.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a group delay characteristic correction device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an amplitude characteristic of each section of a filter.

FIG. 3 is a diagram showing a group delay characteristic of each part of a filter.

FIG. 4 is a general group delay characteristic diagram of a speaker.

FIG. 5 is a configuration diagram of a conventional group delay characteristic correction device.

[Explanation of symbols]

 Reference Signs List 3 IIR high-pass digital filter 4 delay unit 5 IIR low-pass digital filter 6 phase inverter 7 first IIR all-pass filter 8 second IIR all-pass filter 9 adder 10 IIR graphic equalizer

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-256099 (JP, A) JP-A-3-205909 (JP, A) JP-A-4-79600 (JP, A) JP-A-54- 32301 (JP, A) JP-A-59-211399 (JP, A) JP-A-4-312099 (JP, A)

Claims (2)

(57) [Claims] In the group delay characteristic correction apparatus according to claim 1 digitized audio data to be speaker for sound reproduction signal for filtering processing, divides the signal of the digital audio data into a plurality of bands, the first IIR type Digital filter and second II
Have an R-type digital filter, further, the first I
A delay device for delaying by to the output signal of the IR-type digital filter, and a phase inverter for inverting 180 ° the phase of the output signal of the second IIR type digital filter,
And N allpass IIR type digital filter for performing phase adjustment of the output of the phase inverter, this all-pass IIR
Consisting comprises an adder for adding <br/> the output of the output signal and the previous SL delayer type digital filter, and N cascaded graphic equalizer for performing amplitude correction of the output signal of the adder A group delay characteristic correction device, characterized in that: 2. The cascade connection of two all-pass IIR digital filters, and the connection of the graphic equalizer to one
2. The group delay characteristic correcting device according to claim 1, wherein the group delay characteristic correcting device is constituted by a plurality of groups.