JP2709855B2 - Speaker drive circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loudspeaker driving circuit, and in particular, divides a frequency band of an audio signal into a plurality of bands, such as a two-way or three-way system, and The present invention relates to a device for driving a corresponding plurality of speakers.

[Prior Art] Conventionally, as the above-described three-way speaker driving circuit, for example, there is one as shown in FIG. That is, the low-frequency component of the audio signal supplied to the input terminal 2 is extracted by the low-pass filter 6 of the LC network 4,
The mid-band component of the audio signal is extracted by the high-pass filter 8 and the low-pass filter 10 of the LC network 4, and the high-band component of the audio signal is extracted by the high-pass filter of the LC network 4.
The low-frequency component amplifier 14, the mid-frequency component amplifier 16, and the high-frequency component amplifier 18 are respectively amplified by the low-frequency component amplifier 14, the low-frequency component woofer 20, the mid-frequency component squawker 22, It is supplied to the tweeter 24 for the region component. However,
As shown in FIG. 4, woofer 20, squawker 2, tweeter
Since the baffle surfaces 26 of all 24 are the same, the positions of the diaphragms are different from each other, there is a time difference of ta between the squawker 22 and the woofer 20, and tb is between the squawker 22 and the tweeter 24. There is a time difference. Moreover, the use of the high-pass filter 8 and the low-pass filter 10 for extracting the middle-frequency component causes a delay of tc. In order to compensate for the shift of the time axis due to the time difference and the delay, a delay circuit 28 for delaying the low-frequency component by an amount obtained by subtracting the delay by the filter 6 from tc + ta is provided between the low-pass filter 6 and the amplifier 14. , Tc + tb delay circuit 30 for delaying high frequency components
Is provided between the high-pass filter 12 and the amplifier 18.

[Problems to be Solved by the Invention] However, in such a speaker drive circuit, dedicated amplifiers 14, 16, and 18 must be provided for each of the low band, the middle band, and the high band. The band component is supplied to the delay circuit 28, the output of the delay circuit 28 is supplied to the amplifier 14, and the mid band component is further supplied from the LC network 4 to the amplifier 14.
16 and delay circuit for high frequency components from LC network 4
30 and the output of the delay circuit 30 must be supplied to the amplifier 18, and there is a problem that the connection is complicated.

An object of the present invention is to provide a speaker driving circuit that solves the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above object, the first invention provides a first high-pass filter for dividing an input signal into at least two frequency bands, and a first low-pass filter. A first group of filter means having a pass filter; and at least a time axis correcting means provided on an output side of the first low-pass filter, wherein an output of the time axis correcting means and an output of the first high-pass filter are provided. Are added by an adding means, and the output of the adding means is amplified by one amplifying means.
A second high-pass filter split into two frequency bands;
And a second group of filter means having a second low-pass filter. Then, the crossover frequency between the second high-pass filter and the second low-pass filter is set lower than the crossover frequency between the first high-pass filter and the first low-pass filter. I have. Also, in the second invention, the first group of filter means divides the input signal into three frequency bands of a low band, a middle band, and a high band.
, A first band-pass filter, and a first high-pass filter. The time axis correction unit is provided on the output side of the first low-pass filter unit and the output side of the first high-pass filter unit, respectively. The output of the time axis correcting means and the output of the first band pass filter means are added by the adding means and amplified by one amplifying means. A second group of filter means for dividing the output of the amplifying means into three frequency bands of a low band, a middle band, and a high band;
It has a second band-pass filter and a second high-pass filter. Further, the pass band of the second band pass filter is set wider than the pass band of the first band pass filter.

[Operation] According to the first aspect of the invention, the input signal is band-divided by the first group of filter means, the shift of the low-frequency component on the time axis is corrected by the time-axis correction means, and thereafter the high-frequency component is corrected by the addition means. The signal is combined with the band component, amplified by a single amplifier, and band-divided again by the second group of filter. The components near the crossover frequency of the first group of filter means among the high-frequency components that have not been time-axis corrected are added to the second low-pass filter when they are added and re-divided. The crossover frequency between the second high-pass filter and the second low-pass filter of the second group of filter means may be changed by the first high-pass filter of the first group of filter means. And the first low-pass filter, the crossover frequency is set lower than that of the first low-pass filter. Since it is supplied to the high-pass filter side of the second group of filter means, there is no time axis shift. According to the second aspect, the input signal is band-divided by the first group of filter means, the time axis deviation of the low-frequency component and the high-frequency component is corrected by the time-axis correction means, and thereafter, the addition means is used. The signal is combined with the mid-range component, amplified by one amplifier, and band-divided again by the second group of filters. In addition, among the mid-frequency components that have not been subjected to time-axis correction, components near the crossover frequency of the first group of filter means are added and re-divided when the second low-pass filter means, 2, the pass band of the second band-pass filter means of the second group of filter means is wider than the band-pass filter of the first group of filter means. Therefore, of the mid-range components that have not been time-axis corrected, the crossover frequencies of the low-pass filter means and the band-pass filter means of the first group of filter means and the band-pass filter means of the first group of filter means Most of the signals in the vicinity of the crossover frequency of the high-pass filter means are supplied to the band-pass filter means side of the second group of filter means, so that the time axis does not shift.

[Example] In FIG. 1, reference numeral 31 denotes an input terminal, and an audio signal supplied thereto is supplied to a controller 32. The controller 32 includes a woofer low-pass filter 34 for extracting a low-frequency component from the audio signal, a squaker for extracting a mid-frequency component from the audio signal, for example, a low-pass filter 36 and a high-pass filter 38, And a tweeter high-pass filter 40 for extracting a band component. Woofer filter
The low frequency component from 34 is a time axis correction means, for example, a delay circuit
The signal is supplied to an adder 44 via a
Is supplied to the adder 44 as it is, and the high-frequency component from the tweeter filter 40 is supplied to the adder 44 via time axis correction means, for example, a delay circuit 46.

The output of the adder 44 is amplified by one amplifier 48 before being supplied to the LC network 4. This LC network 4 is configured in the same way as the LC network 4 shown in FIG.
It is divided into three components, a middle range and a high range, and the low range is supplied to the woofer 20, the middle range is supplied to the squawker 22, and the high range is supplied to the tweeter 24.

As the delay circuit 42, for example, various types such as a digital delay circuit and an analog delay circuit can be used.
In particular, as an analog delay circuit, a leading edge of an audio signal is detected by an edge detection circuit, a control signal is generated based on the detected signal, and the attenuator blocks or attenuates the audio signal for a set time from the leading edge of the audio signal. In addition, a device that performs a function equivalent to a delay can be used. The delay times of the delay circuits 42 and 46 are the time difference ta between the squawker 22 and the woofer 20 and the squawker 22 and the tweeter 24 shown in FIG.
In consideration of the time difference tb with respect to the delay time, the high-pass filter 8 in the controller 32, the mid-range delay due to the low-pass filter 10, and the mid-range delay in the LC network 4, the time axis of the low- and high-frequency components is It is set to match the time axis of the component.

As shown in FIGS. 2B and 2D, the crossover frequency between the woofer filter and the squawker filter in the LC network 4 is determined by the woofer filter 34 in the controller 32, the squawker filter 36, and the like. 38
The crossover frequency between the squawker filter and the tweeter filter in the LC network 4 is set lower than the controller.
The crossover frequency between the squawker filters 36 and 38 and the tweeter filter 40 in 32 is set higher. That is, the band of the squawker filter in the LC network 4 is set wider than the bands of the squawker filters 36 and 38 in the controller 32.

In the loudspeaker driving circuit thus configured, when an audio signal having a band as shown in FIG. 2A is input to the input terminal 31, each of the loudspeakers has a frequency band as shown in FIG. The woofer filter 34, the squawker filters 36 and 38, and the tweeter filter 40 perform band division into low, middle, and high bands, respectively. The signal is re-synthesized by the mixer 44 as shown in FIG. 2 (c). The re-synthesized audio signal is amplified by the amplifier 48 and supplied to the LC network 4. In the LC network 4, the re-synthesized audio signal is again band-divided into a low band, a middle band, and a high band, and supplied to the corresponding woofer 20, squawker 22, and tweeter 24.

Here, the reason why the crossover frequency between the LC network 4 and the controller 32 is slightly shifted is as follows. That is, in the controller 32, the audio signal is band-divided into a high-frequency component, a mid-frequency component, and a low-frequency component, and thereafter, the high-frequency component and the low-frequency component are delayed, and re-synthesized with an undelayed mid-frequency component. , And again in the LC network 4 into low, middle, and high bands. At this time, a mid-range component, which is a frequency component near both crossover frequencies, that has passed through the squawker filters 36 and 38 and has not been delayed, is subdivided in the LC network 4 when the woofer 20 and the tweeter 24 May be supplied to When the non-delayed component is supplied to the woofer 20 and the tweeter 24, the sound is radiated earlier than the squawker 22 by the time difference ta and tb, as shown in FIG. 4, deviating from the purpose of simultaneous (in-phase) output. , Impair sound quality. Therefore, if the band of the squawker in the LC network is made wider than the band of the squawker in the controller 32, as shown by the hatching in FIG. 2D, the undelayed mid band components are radiated from the woofer 20 and the tweeter 24. Is very slight and does not impair the sound quality. Conversely, as indicated by the dotted lines in FIG. 2 (d), the delayed low-frequency component and high-frequency component are slightly acoustically radiated from the squawker 22, but the delay in the delay circuits 42 and 46 is reduced by the mid-range component. Therefore, even if sound is radiated from the squawker 22, no adverse effect occurs.

In the above-described embodiment, the frequency band is divided into three parts of a low band, a middle band, and a high band. However, the frequency band is divided into a low band (for a woofer) and a middle and high band (for a squawker and a tweeter), and a two-way speaker system is formed. You may make it apply. In this case, if the diaphragm of the speaker for the woofer is located before the diaphragm of the speaker for the squawker and the tweeter, the crossover frequency between the filter for the mid-high range and the filter for the low speed in the LC network is set to the mid-high frequency in the controller. What is necessary is just to set a little lower than the crossover frequency of the band filter and the low band filter. Note that, even in the case of a two-way speaker system, the positional relationship of the diaphragm of each speaker may be different from the above-described positional relationship depending on the relationship between the size and the mounting position of the speaker. In that case, the crossover frequency between the middle-high band filter and the low band filter in the LC network may be set slightly higher than the crossover frequency between the middle-high band filter and the low band filter in the controller.

[Effects of the Invention] As described above, according to the present invention, the audio signal is divided into bands, and after the time axis of the component requiring the time axis correction is corrected, the audio signal is recombined to perform Since the audio signal synthesized by the amplifier is amplified, divided into bands again, and supplied to the speakers, the entire band can be amplified by one amplifier. Since it is only necessary to supply the output from the amplifying means to the filter means (LC network 4 in the embodiment), the connection is also simplified. In addition, the crossover frequency of each filter of the second group of filter means for dividing the frequency band to be supplied to the speaker is controlled by the filters of the first group of filter means (each filter in the controller 32) which is divided for time axis adjustment. Since the crossover frequency is shifted, the sound quality is not impaired.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of a speaker driving circuit according to the present invention, FIG. 2 is a waveform diagram of each part of the embodiment, FIG. 3 is a block diagram of a conventional speaker driving circuit, and FIG. FIG. 2 is a configuration diagram of a speaker driven in the present embodiment. 4 LC network (second filter means), 34, 3
6, 38, 40 ... first filter means, 42, 46 ... delay circuit (time axis correction means), 44 ... addition means, 48 ... amplification means.

Claims (2)

(57) [Claims] 1. A first group of filter means, comprising: a first high-pass filter; and a first low-pass filter, for dividing an input signal into at least two frequency bands; Time axis correcting means provided at least on the output side of the pass filter means, adding means for adding the output of the time axis correcting means and the output of the first high-pass filter, and amplifying the output of the adding means A second group of filter means having one amplifying means, a second high-pass filter, and a second low-pass filter for dividing an output of the amplifying means into at least two frequency bands; And the crossover frequency between the second high-pass filter and the second low-pass filter is set lower than the crossover frequency between the first high-pass filter and the first low-pass filter. Have been Peaker drive circuit. 2. A first low-pass filter, a first band-pass filter, and a first high-pass filter for dividing an input signal into three frequency bands of a low band, a middle band, and a high band. A first group of filter means having: a first low-pass filter means and a first high-pass filter means; and time-axis correction means provided on the output side of the first high-pass filter means. Adding means for adding the output of the first band-pass filter means; one amplifying means for amplifying the output of the adding means; and three frequencies of low, middle and high frequencies for the output of the amplifying means Second low-pass filter means for dividing into band, second
And a second group of filter means having a second band-pass filter means and a second high-pass filter means, wherein the pass band of the second band-pass filter means is higher than the pass band of the first band-pass filter means. Speaker drive circuit also widely set.