JPH04371007A - Low band correcting device for audio equipment on vehicle - Google Patents

Abstract

PURPOSE:To correct the reduction of the sound pressure in the low band by making monaural signals of low frequency parts of Lch and Rch on the rear side to prevent the phase inference and preliminarily presetting the phase of the rear side to equalize phases of sounds from speakers on the front side and the rear side to each other at a listening point. CONSTITUTION:Signals fl, fr, rl and rr of Lch and Rch on the front side and the rear side pass preamplifiers 1 to 4, and signals fl and fr are directly amplified power amplifiers 5 and 6 and are outputted to speakers FL and FR. Signals rl and rr are inputted to high pass filters 7 and 8 and low pass filters 9 and 10 and are divided to middle and high frequency parts and low band parts. Monaural signals obtained by adding these output signals in an adder 11 have phases changed by a variable phase shifter 12, and the output of the filter 7 as the middle and high frequency part of the signal rl and the output of the filter 8 as that of the signal rr are synthesized by adders 13 and 14, and results are outputted to speakers RL and RR through power amplifiers 15 and 16.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency correction device for in-vehicle audio.

0002

2. Description of the Related Art Unlike home audio, in-vehicle audio often lacks a low frequency range because a sufficient back cavity cannot be provided due to speaker installation conditions. Furthermore, as the vehicle is running, the low range is masked by road noise, wind noise, etc., resulting in an audible lack of low range.

[0003] For this reason, a 3D woofer as shown in FIG. 5 has been conventionally used as a first method for correcting this lack of low frequency range. Furthermore, as a second method, as shown in FIG. 6, the low range can be corrected by boosting the low range using the output frequency characteristic of the amplifier.

0004

[Problems to be Solved by the Invention] However, in the conventional car audio low frequency correction device described above, the first 3D
The method using a woofer requires a space to place the woofer speaker, and also requires an amplifier dedicated to the woofer and wiring for the woofer, resulting in high costs. The second method of boosting the low range has the problem that when the volume is increased, the low range is distorted first, resulting in a harsh sound quality.

Furthermore, conventionally, as shown in FIG.
Because the sound reaches the listener from each of the rear Lch and Rch speakers, and because the listening point in the vehicle is offset to the left and right, phase differences are likely to occur, especially in the low frequency range. When this occurs, there is a problem in that the sound pressure in the low range decreases.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and an object thereof is to provide an excellent low-frequency correction device for in-vehicle audio that can correct low-frequency ranges at low cost.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a filter circuit for extracting the low frequency portion of Lch and Rch on the rear side, and a filter circuit for extracting the low frequency portion of the Lch and Rch on the rear side. A circuit for synthesizing the output and the rear Lc
A phase shifter circuit that changes the phase characteristics of the output of the low frequency range of h and Rch, a filter circuit that extracts the middle and high frequency range of the rear Lch and Rch, and a rear Lch and Rch
A circuit is provided for synthesizing the output of the middle and high range portions of the H and the output of the phase shifter circuit, thereby making it possible to correct the auditory lack of low frequencies.

[0008]

[Operation] Therefore, according to the present invention, the phase on the rear side is preset in advance so that the phase of the low frequency range of the audio output from the front and rear Lch and Rch speakers is matched at the listening point. Okay, rear Lc
By combining the low-frequency outputs of h and Rch to prevent phase interference, it is possible to correct the decrease in low-frequency sound pressure caused by the phase difference.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of an embodiment of the present invention. 2 and 3 are principle diagrams showing the principle of the present invention. The principle of the present invention is that, as shown in Fig. 2, the rear Lch
By converting the low frequency parts of the Lch and Rch into monaural signals, phase interference between the Lch and Rch can be prevented, and as shown in FIG. This means presetting the rear phase in advance so that the phases match at the listening point.

Next, the configuration and operation of the embodiment will be explained with reference to FIG. In FIG. 1, fl, fr, rl, and rr are front and rear Lch and Rch signals, respectively, and these signals pass through preamplifiers 1, 2, 3, and 4. Of these, fl and fr are directly connected to power amplifiers 5 and 6.
The power of the signal is amplified and output to the speakers FL and FR, respectively. rl and rr are high-pass filters 7 and 8, respectively.
Then, the signals are input to low-pass filters 9 and 10, and are divided into a middle-high frequency band and a low-frequency band, respectively. The crossover frequency needs to be set to 100 Hz or less, considering that the low frequency parts of musical sounds (especially bass, bass drum, etc.) are often recorded so as to be localized in the center.

The signals output from the low-pass filters 9 and 10 are added together by an adder 11 to become a monaural signal. The signal output from the adder 11 is sent to the variable phase shifter 1
2 and the phase can be varied. The signal output from the variable phase shifter 12 is combined with the output of the high-pass filter 7, which is the mid-high range part of rl, and the output of the high-pass filter 8, which is the mid-high range part of rr, by an adder 13 and an adder 14, respectively. Ru. The outputs of adders 13 and 14 are input to power amplifiers 15 and 16, respectively, and are output to speakers RL and 14, respectively.
Output to RR.

As described above, the phase characteristics of the low frequency portion of the audio output from the speakers RL and RR can be easily varied by changing the characteristics of the variable phase shifter 12. Therefore, the optimal phase characteristics can be adjusted by reproducing this device in a target vehicle and measuring the sound pressure characteristics of each speaker at the listening point with a spectrum analyzer.

[0013]

[Effects of the Invention] As described above, the present invention provides rear Lch
By converting the low-frequency parts of the Lch and Rch into monaural signals, phase interference between the Lch and Rch is prevented, and the low-frequency phases of the audio output from the front and rear speakers are matched at the listening point. By presetting the rear side phase in advance, it is possible to correct the drop in sound pressure in the low range at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a low-frequency correction device for in-vehicle audio according to an embodiment of the present invention.

[Figure 2] Diagram of the operating principle in the same embodiment

[Figure 3] Diagram of the operating principle in the same embodiment

[Figure 4] Diagram of operating principle in conventional example

[Figure 5] Example of use of woofer in conventional example

[Figure 6] Example of using low-range boost in conventional example

[Explanation of symbols]

7 High pass filter 8 High pass filter 9 Low pass filter 10 Low pass filter 11 Adder 12 Variable phase shifter circuit 13 Adder 14 Adder

Claims (1)

[Claims] 1. A filter circuit for extracting low frequency parts of rear Lch and Rch in order to perform low frequency correction of vehicle interior acoustic characteristics in in-vehicle audio;
a circuit for synthesizing the low-frequency outputs of h and Rch, a phase shifter circuit that changes the phase characteristics of the low-frequency outputs of the rear Lch and Rch, and a rear Lch and Rch circuit.
A low frequency correction device for vehicle audio, comprising a filter circuit that extracts the middle and high frequency parts of the rear Lch and Rch, and a circuit that synthesizes the output of the middle and high range parts of the rear Lch and Rch and the output of the phase shifter circuit.