JPH0879880A - Speaker system - Google Patents

Abstract

PURPOSE: To obtain a small sized and inexpensive speaker system in which a filter scale and a group delay are reduced. CONSTITUTION: Inverse filters 2L,2R correcting a response characteristic of a speaker are formed by 1st filters 3L, 3R with IIR filters having a bell characteristic at a specific frequency band and 2nd filters 4L,4R with FIR filters acting like convolvers in cascade connection and the characteristic of the 1st filters 3L, 3R is selected so that the filter coefficient length of the 2nd filters 4L, 4R is optimized to be a prescribed length by an audio signal processing unit, and when the inverse filters are used to correct the transmission system including the speaker and to reproduce an audio signal in which distorted sound of the transmission system is not heard, the filter scale and the group delay are reduced to attain miniaturization and low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker device which corrects a response characteristic of a transmission system including a speaker by an inverse filter to prevent distorted sound.

[0002]

2. Description of the Related Art In recent years, in multimedia, it is required to improve the quality of audio sound accompanying an image. This is not a mere sound as audio with a wide dynamic range by CD-ROM has spread.
Because Fi audio became indispensable. In this case, the speaker is required to be small and have high performance. For such a purpose, on the one hand, a faithful reproduction of a three-dimensional sound field including a sound field and a sound image such as a sound field (surround) and a sound image (3D virtual reality) for HiFi audio is sought, and on the other hand, a speaker. There is an increasing demand for audio reproduction in which the response characteristics of the transmission system including the speaker are corrected by an inverse filter so that the distorted sound of the transmission system cannot be heard, and various attempts have been made in the latter as well. .

Conventionally, for example, Japanese Patent Laid-Open No. 3-143195 discloses a linear phase FIR type filter (FIR: Finite Impulse Respo) for each of a plurality of frequency band channels.
(nse) is provided, and a so-called multi-way speaker system is disclosed in which the characteristics as a speaker system and the sound quality are improved by performing digital signal processing suitable for a speaker unit corresponding to each of a plurality of frequency bands. ing.

As digital filters, FIR type filters and IIR type filters (IIR: Infinite Impul)
se response) is used at the same time.
-79725 and JP-A-63-221708. Among these, Japanese Patent Laid-Open No. 57-79725 discloses that the FIR type filter is used to remove the resonance characteristic in which the amplitude changes near the roll-off frequency outside the pass band of the IIR type filter. Further, Japanese Patent Laid-Open No. 63-221708 discloses an FIR type filter that variably adjusts the amplitude and an all-pass type IIR type filter that variably adjusts the group delay amount.

[0005]

However, in the above-mentioned publication, if the speaker characteristics are corrected only by the FIR type filter, the filter scale (filter coefficient length) must be made extremely large, and conversely, Smaller sizes (smaller ones) have to sacrifice performance, and therefore very large, or poorly performant, filter size (coefficient length) and group delay amounts. There is no disclosure of making it short, compact, and built into the speaker enclosure.

The present invention has been made in order to solve the above-mentioned problems of the conventional example, and an object thereof is to obtain a small-sized and inexpensive speaker device by shortening the filter scale and the group delay amount. is there.

[0007]

In order to achieve the above object, a speaker device according to the present invention includes an inverse filter for correcting the response characteristic of a speaker in a predetermined frequency band, such as a bell type filter in a specific frequency band. A first filter configured by an IIR type filter having a desired characteristic and a second filter configured by an FIR type filter operating as a convolver are connected in cascade, and the characteristic of the first filter is set by the second filter. The audio signal processing device is set so that the filter coefficient length of the filter is optimized to a predetermined length.

Further, according to the present invention, a plurality of multi-way type speakers are provided as the speaker, and the response characteristics of all the speakers are corrected by one inverse filter without dividing each channel. To do.

Further, the present invention is characterized in that such an inverse filter is arranged in each system of a stereophonic sound field control section composed of a pair of convolvers.

[0010]

【Example】

First Embodiment FIG. 1 is a system configuration diagram showing a speaker device according to a first embodiment. In FIG. 1, two-channel stereo sound sources 1L and 1R generate desired audio signals. The inverse filter 2L is a cascade-connected first and second filter 3L for correcting speaker output characteristics and realizing speaker reproduction with flat sound pressure characteristics and phase characteristics.
And 4L and is for the left (L) channel system. The first filter 3L is composed of an IIR type filter having a bell-shaped characteristic that is enhanced / attenuated with respect to a 0 dB reference value by setting a center frequency and Q (sharpness) in a specific frequency band. On the other hand, the second filter 4L is composed of a convolver, which is a convolution operation processing circuit composed of an FIR filter that corrects the residual amplitude and phase characteristics of the first filter 3L excluding the bell-shaped characteristics. Further, the characteristic of the first filter 3L is set so as to optimize the filter coefficient length of the second filter 4L to a predetermined length. Reference numeral 2R is an inverse filter of the right (R) channel system, which includes first and second filters 3R and 4R similar to the left channel system.

Further, the output of the left channel convolver 4L is connected to a plurality of amplifiers 5L1 to 5L3 constituting a network provided for each channel of each frequency band of the left channel multiway system. The amplifiers 5L1 to 5L3 are connected to the speakers 6L1 to 6L3, respectively, when they correspond to each other. 5R1 ~ 5R3
Similarly, 6R1 to 6R3 are a plurality of amplifiers and speakers that form a network provided for each channel of each frequency band of the right channel multiway system, and these left channel system and right channel system speakers are each frequency The above-described one inverse filter 2L for the left channel system and the right channel system without being divided for each channel for each band
And 2R correct the output characteristics of all the speakers, respectively, and realize speaker reproduction with flat sound pressure characteristics and phase characteristics.

Further, the control unit 7 includes the inverse filters 2L and 2R.
Of the coefficient memory 8 such as a ROM.
Are connected to the control unit 7. In this coefficient memory 8,
The second filter 4 (collective term for 4L and 4R) stores in advance coefficients relating to the output characteristics of the speaker when performing the convolution operation, and the control unit 7 controls the first filter 3 to store the coefficients.
Bell frequency characteristic center frequency and Q
Is set and the coefficient is read from the memory 8 to perform convolution calculation processing on the time axis based on the coefficient, and the output characteristics of the speakers 6L1 to 6L3 and 6R1 to 6R3 are corrected by the inverse characteristics thereof and the sound pressure characteristics are corrected. Also, the reproduction of a speaker having a flat phase characteristic is realized.

That is, as shown in FIG. 1, a speaker correction system (audio signal processing device) according to the present invention.
Is a speaker system of a two-channel stereo system, and includes left and right channel inverse filters 2L and 2R, a control unit 7, and a memory 8. The left (L) channel speaker correction system (audio signal processing device) is
The sound source 1L, the inverse filter 2L, the amplifiers 5L1 to 5L3 and the speakers 6L1 to 6L3, and the speaker correction system for the right (R) channel system includes the sound source 1R, the inverse filter 2R, the amplifiers 5R1 to 5R3 and the speakers 6R1 to 6L.
Composed of R3.

By the way, in the above structure, it is general to use an FIR type filter as the inverse filter. However, if the inverse filters 2L and 2R are constituted by only the FIR type filter, for example, the present inventors conducted experiments. In the example (characteristic shown in FIG. 3 described later), the sampling frequency is 32 KH.
In z, the number of taps (filter coefficient length) is about 1200.
Above (delay time = 1200 x (1/3200) x 1/2
= 0.1875 seconds) is required. In addition to this, if an FIR type filter of the same scale is used in the three-dimensional sound field control, it takes 0.1875 seconds, which results in a delay of 0.375 seconds. This is larger than the allowed 0.33 seconds per frame.

However, it is necessary to shorten the filter scale (coefficient length) in order to reduce the time lag (delay) from the image, and the advantage that it can be incorporated in the speaker if it is downsized. is there. Therefore, it is conceivable to use an IIR type filter that has no time lag auxiliaryly to significantly reduce the filter scale. In this way, the HiFi audio sound can be enjoyed even in multimedia. In this embodiment, an FIR type filter and an IIR type filter are connected in series as an inverse filter, and at this time, a bell type characteristic is adopted as the IIR type filter, and the filter characteristic is the filter coefficient length of the FIR type filter. Set to optimize for a given length. The bell-shaped characteristic does not have a sharp roll-off like the band-pass characteristic but has a gentle slope depending on Q (sharpness), so that the slope can be easily set adaptively.

Next, a method of calculating the bell-shaped characteristic of the IIR filter will be described. 2 shows an amplitude characteristic before correction (A) of the transmission system in the case where the inverse filter is not provided in FIG. 1, and FIG. 3 shows a case where only the second filter 4 is provided as the inverse filter 2 (general term for 2L and 2R). 3 shows corrected amplitude characteristics (B) and (C) of the transmission system of FIG. 3, respectively, and in FIG. 3, the amplitude characteristics (B) is the number of taps (filter coefficient length) 1
The amplitude characteristic and the amplitude characteristic (C) when realized by the inverse filter 200 of FIG. Further, FIG. 4 shows a bell-shaped characteristic, and FIG. 5 shows a target characteristic A for correction.
6 shows the target characteristic B of the new correction, and FIG. 6 shows the number of taps (filter coefficient length) 300 shown in comparison with the amplitude characteristic (B) when only the second filter 4 having the number of taps (filter coefficient length) 1200 is provided. 5 shows the amplitude characteristic C corrected by the inverse filter 2 having the second filter 4 and the first filter 3 having the bell-shaped characteristic shown in FIG.

Now, as shown in FIG. 3, the number of taps (filter coefficient length) is 12 as the corrected amplitude characteristic of the transmission system when only the second filter 4 is provided as the inverse filter 2.
When the number of taps is small as in the amplitude characteristic (C) in the case of the number of taps (filter coefficient length) 300 compared to the amplitude characteristic (B) in the case of 00, the number of taps (filter It can be seen that the error between the amplitude characteristic (B) in the case of (coefficient length) 1200 and the target characteristic A shown in FIG. That is, if the number of taps (filter coefficient length) is reduced and the filter scale is reduced (downsized), the performance is adversely affected.

Therefore, from the amplitude characteristic (C) in the case of the number of taps (filter coefficient length) 300 shown in FIG. 3, a bell-shaped characteristic in which the center frequency is lowered by 5 dB at 150 Hz as shown in FIG. 4 is taken out, which is contrary to this. First correction is performed by the first filter 3 set as the IIR type filter of the characteristic, and then a new correction target characteristic B which is the characteristic obtained by removing the bell characteristic from the correction target characteristic A shown in FIG. 5 is obtained. When corrected by the second filter having 300 taps, the amplitude characteristic C shown in FIG. 6 is obtained. In particular, it can be seen that the amplitude characteristic C has a smaller error from the target characteristic than the amplitude characteristic (C) shown in FIG. That is, by setting the characteristics of the first filter 3 so as to optimize the filter coefficient length of the second filter 4 to a predetermined length, the filter scale can be reduced and the multimedia HiFi audio can be embedded in the speaker. Can allow you to enjoy comfortably.

Although not described in detail, as another characteristic calculation method of the bell-shaped characteristic, the bell target BT may be directly obtained from the amplitude characteristic (A) as shown in FIG. 2, for example. Also, here, the number of bell targets BT is not limited to one but may be two or more depending on the amplitude characteristics. In order to specify the center frequency and Q (sharpness) of such a bell type, a bell analysis routine (by sweeping each parameter within a predetermined band) is operated on the workstation to synthesize the IIR type filter and the FIR type filter. The characteristics are repeatedly obtained until finally within a predetermined deviation.

Therefore, according to the first embodiment, the inverse filter 2 for correcting the response characteristic of the speaker in the predetermined frequency band.
Is configured by connecting in series a first filter 3 configured by an IIR type filter having a bell-shaped characteristic in a specific frequency band and a second filter 4 configured by an FIR type filter operating as a convolver, and By constructing an audio signal processing device that sets the characteristics of the first filter 3 so that the filter coefficient length of the second filter 4 is optimized to a predetermined length, the inverse filter 2
When correcting the response characteristics of the transmission system including the speaker and performing audio playback so that the distorted sound of the transmission system cannot be heard,
The filter scale can be reduced, and for example, multimedia HiFi audio can be comfortably enjoyed by being built in the speaker enclosure.

As speakers, a plurality of multiway speakers 6L1 to 6L3 and 6R1 to 6R3 are provided.
One inverse filter 2L, 2 without dividing for each channel
Since all the speakers are corrected by R,
The audio signal processing device for correcting the speaker can be incorporated in the speaker, the processing device section becomes inexpensive, and the speaker device can be downsized.

Second Embodiment Next, FIG. 7 illustrates a speaker device according to a second embodiment. (A) is an external structural view and (b) is a circuit configuration diagram of an internal audio signal processing device. is there. In this second embodiment, as shown in the external structure of FIG. 7A, a multi-way speaker system is adopted as in the configuration of the first embodiment shown in FIG. Each of the speakers 6L1 to 6L3 is not driven by an individual amplifier, but is driven by a single amplifier 5L, and the amplifier 5L and an inverse filter are integrated by the processing circuit unit 9 and incorporated in the speaker device. I am trying.
Further, it is provided with an infrared light receiving unit 10 for receiving a sound source and a remote control (volume / on / off) command by an infrared ray from a main body 20 such as a player or a display. 1
Reference numeral 1 is a conversion unit that converts the infrared light received by the infrared light receiving unit 10 into a reception signal, 12 is a distributor that distributes the converted reception signal to the control unit 7 and the inverse filter 2L, and 13 is a drive signal via the amplifier 5L. Shows a distributor for distributing each of the speakers to each of the speakers 6L1 to 6L3. Further, the same structure as the left channel system is also provided in the right channel system.

Therefore, according to this second embodiment, each speaker of the multi-way speaker system is not driven by an individual amplifier, but a single amplifier 5L is used.
Since the amplifier 5L and the inverse filter are integrated by the processing circuit unit 9 and incorporated into the speaker device, the processing circuit unit 9 can be constructed at low cost and the speaker device can be improved in performance. Miniaturization can be achieved. In addition, since the command is given by infrared rays, the speaker device can be placed at an optimum distance for easy stereo localization with good mobility, and it is provided separately from the main body of the player, display, etc. There is no leakage, and the computer of the main body can be provided with beautiful features such as no adverse effects such as vibration. It is especially suitable for multimedia audio systems.

Third Embodiment Next, FIG. 9 shows a block diagram of a speaker device according to a third embodiment in combination with a three-dimensional sound field control. The speaker device according to the third embodiment shown in FIG. 9 includes an inverse filter 2L according to the first embodiment in each system of a stereoscopic sound field control unit including sound image localization filters 14L and 14R including a pair of convolvers.
And 2R are provided, and the controller 7 adjusts the pair of sound image localization filters 14L and 14R, so that the virtual speaker 6 is placed at an arbitrary position by the two speakers 6L and 6R.
I can be replayed as is. In addition, 15 is C
D-ROMs, 16a to 16c are sound source data of the CD-ROM 15, localization data and video data, and 17 is a display for displaying video data.

With this configuration, the total time delay is reduced, and even when combined with the stereophonic sound field control, the time delay can be suppressed to less than one frame of the image, which hinders multimedia reproduction. Never give. Although not described in detail here, in each of the above-described embodiments, in order to supplement the bass that is generally deficient in small speakers, for example, NFB (negative feedback) technology is adopted at a low frequency of 60 to 200 Hz, and It goes without saying that the sound quality may be improved.

[0026]

As described above, according to the present invention, the inverse filter for correcting the response characteristic of the speaker in the predetermined frequency band has an IIR having a bell-shaped characteristic in a specific frequency band.
Type filter constituted by a first filter and a second filter constituted by an FIR type filter operating as a convolver are connected in cascade, and the characteristics of the first filter are defined by the filter coefficient length of the second filter. Since it has an audio signal processing device set to be optimized to a predetermined length, the inverse filter corrects the response characteristics of the transmission system including the speaker and reproduces audio so that distortion of the transmission system is not heard. In this case, the size of the filter and the amount of group delay can be shortened to obtain a small and inexpensive speaker device.

Further, as a speaker, a plurality of multi-way type speakers are provided, and all the speakers are corrected by one inverse filter without being divided for each channel, whereby audio signal processing for correcting the speakers is performed. The device can be made small and inexpensive, and it can be installed in the speaker, so that multimedia HiFi audio can be enjoyed comfortably.

Further, by providing an inverse filter in each system of the stereophonic sound field control section consisting of a pair of convolvers,
Even when combined with the stereoscopic sound field control, the time delay can be suppressed to the time less than one frame of the image, and there is an effect that the multimedia reproduction is not hindered.

[Brief description of drawings]

FIG. 1 is an overall block diagram showing a first embodiment of a speaker device of the present invention.

FIG. 2 is a characteristic diagram showing an amplitude characteristic (A) before correction of the transmission system in the case where an inverse filter is not provided in FIG.

FIG. 3 is a characteristic diagram showing corrected amplitude characteristics (B) and (C) of a transmission system in the case where only a second filter 4 is provided as an inverse filter 2 (general term for 2L and 2R) in FIG. And the amplitude characteristic (B) is the number of taps (filter coefficient length)
The characteristics when realized by the inverse filter of 1200 and the amplitude characteristics (C) show the characteristics when realized by the same 300.

FIG. 4 is a characteristic diagram of a bell-shaped characteristic.

FIG. 5 is a characteristic diagram showing a correction target characteristic A and a new correction target characteristic B.

FIG. 6 is a diagram showing a second filter 4 having a number of taps (filter coefficient length) 300 shown in comparison with an amplitude characteristic (B) in the case where only the second filter 4 having a number of taps (filter coefficient length) 1200 is provided. 6 is a characteristic diagram showing an amplitude characteristic C corrected by an inverse filter 2 having a bell-shaped characteristic first filter 3 shown in FIG.

FIG. 7 is an external view of a speaker device according to a second embodiment of the present invention and a block diagram of an internal processing circuit.

FIG. 8 is an external view of a speaker device according to a second embodiment of the present invention and a block diagram of an internal processing circuit.

FIG. 9 is an overall block diagram showing a third embodiment of the speaker device of the present invention.

[Explanation of symbols]

1L, 1R Sound source 2L, 2R Inverse filter 3L, 3R First filter (IIR type filter) 4L, 4R Second filter (FIR type filter, convolver) 5L1 to 5L3, 5R1 to 5R3 Amplifier 6L1 to 6L3, 6R1 to 6R3 Amplifier 7 Control unit 8 Memory 14L, 14R Convolver (sound localization filter)

Front page continuation (72) Inventor Takeo Tsubooka 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Co., Ltd. (72) Inventor Yasuo Sato 3--12 Moriya-cho, Kanagawa-ku, Yokohama Within Victor Company of Japan, Ltd.

Claims (3)

[Claims] 1. A first filter having an inverse filter for correcting a response characteristic of a speaker in a predetermined frequency band, which is composed of an IIR type filter having a desired characteristic in a specific frequency band, and an FIR type filter operating as a convolver. An audio system in which the characteristics of the first filter are set so as to optimize the filter coefficient length of the second filter to a predetermined length. A speaker device having a signal processing device. 2. A plurality of multi-way type speakers are provided as the speakers, and all the speakers are corrected by one inverse filter without being divided for each channel. The speaker device described. 3. The speaker according to claim 2, wherein the inverse filter is arranged in each system of a stereophonic sound field control unit configured by a pair of convolvers to control a stereophonic sound field including a sound field and a sound image. apparatus.