JPH07120911B2 - Equalizer circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an equalizer circuit that corrects the sound quality and frequency characteristics of a reproduced sound so that the reproduced sound is reproduced in a state close to the original sound in a reproduced sound field. In particular, the present invention relates to an equalizer circuit having an ideal phase characteristic.

[Prior Art and Problems to be Solved by the Invention] In recent years, audio amplifiers that are generally used,
Especially for audio amplifiers installed in automobiles,
It incorporates an equalizer circuit that corrects the acoustic characteristics peculiar to the vehicle interior, which is the sound field, and corrects the sound quality and frequency characteristics of the reproduced sound so that the reproduced sound by the amplifier is reproduced in a state close to the original sound.

As this equalizer circuit, an NFB type having an arrangement as shown in FIG. 5 is generally used.

This NFB type equalizer circuit is one in which a kind of filter circuit 2 having frequency selectivity is connected to the feedback circuit of the NFB amplifier 1, and the filter circuit 2 is provided with, for example, a sixth Various circuits constituted by R and C as shown in the drawing or FIG. 7 are used.

For example, when listening to an ideal sound close to the original sound in a room having a frequency characteristic as shown by the frequency characteristic curve A in FIG. Connect the slow-pass filter, band-pass filter, and high-pass filter having the structure shown in Fig. 8 as shown in Figs. 8A and 8B to give the characteristics shown by the frequency characteristic curve B in the same figure. If reproduced with an amplifier having an equalizer circuit, the peak portion of the frequency characteristic curve of the room is corrected, and the sound with a flat frequency characteristic is obtained over a wide range of frequencies as shown by the frequency characteristic curve of FIG. Is reproduced, and in terms of frequency characteristics, reproduction is performed in a state close to the original sound. As described above, conventionally, an equalizer circuit capable of correcting the sound field characteristic in the vehicle interior is provided in the amplifier, and even in a vehicle interior where conditions are not so good, it is possible to listen to music or the like in a relatively good state. I was able to do it.

However, such a conventional equalizer circuit can be flattened by the equalizer circuit in terms of frequency characteristics, but is very unsatisfactory in terms of phase characteristics.

That is, in the case of this equalizer circuit, when the phase characteristic is measured with a measuring instrument by sequentially increasing or decreasing the frequency with a single tone composed of a sine wave, the phase characteristic curve shown by D in FIG. A characteristic that does not vary much over almost the entire area can be obtained. However, this phase characteristic is a curve obtained as a result of combining the phase characteristic curve E of the low-pass filter, the phase characteristic curve F of the band-pass filter, and the phase characteristic curve G of the high-pass filter. In the area where the phase characteristic curves of the filter of (1) overlap, phase distortion occurs due to the phase difference, resulting in deterioration of sound quality, turbidity, and unclear localization of the sound image. This phase distortion becomes particularly large at the point where the frequency characteristic curves of the filters overlap, that is, near the dip point. This is because the equalizer circuit is a feedback system circuit.

By the way, although sound quality has been improved from the past,
The improvement that has been made conventionally is, as described above, in terms of how to reproduce level-flat frequency characteristics in the sound field. However, when higher quality sound is required, the above-mentioned phase distortion cannot be ignored. The phase of the reproduced sound is
It is an important factor for localization of sound image, so it has a sense of presence, transparency, or no fatigue even after listening for a long time. Sound, in short, is an especially important improvement item when pursuing natural sound reproduction.

[Object of the Invention] The present invention has been made in order to solve the above-mentioned conventional problems, and is capable of reproducing natural sound without phase distortion by a relatively simple circuit. The purpose is to provide a possible equalizer circuit.

SUMMARY OF THE INVENTION The present invention for achieving the above object is an equalizer circuit that corrects the sound quality and frequency characteristics of a reproduced sound so that the reproduced sound in various sound fields can be reproduced in a state close to the original sound. Therefore, in the frequency range higher than around 1 KHz, the phase of the input audio signal has characteristics such that it advances as the frequency of the audio signal becomes higher, and from about 1 KHz to 5 KHz in order to give a sense of perspective. A mid-range correction and high-range correction circuit in which a resistor and a capacitor are connected in parallel or in series, having a circuit constant that relatively advances the phase of the frequency
And, in a frequency region lower than about 1 KHz, the phase of the input audio signal has such a characteristic that it delays as the frequency of the audio signal becomes lower, and the peak of the resonance frequency of the reproduced sound field is It consists of a low-frequency correction circuit in which resistors and capacitors are connected in parallel or in series and which have circuit constants with opposite characteristics. These correction circuits enable the phase characteristics in continuous frequency to be measured. It is characterized by passively adjusting.

With this equalizer circuit, phase distortion can be eliminated, the front and rear relationship of the sound source can be clarified, and it becomes possible to make the sound more natural than ever before.

Embodiments of the Invention Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of an equalizer circuit according to the present invention.

This circuit is composed of a resistor and a capacitor, as shown in the figure.Capacitor C _1L, resistor R _1L , capacitor C
A parallel circuit of _2L and a resistor R _2L constitutes a left high-pass filter, and a parallel circuit of a capacitor C _1R and a resistor R _1R , a capacitor C _2R and a resistor R _2R constitutes a right high-pass filter. And capacitor C
_3L , the capacitor C _4L, and the resistor R _{3L form a} left low-pass filter, and the capacitor C _3R , the capacitor C _4R, and the resistor R _{3R form a} right low-pass filter. Of these capacitors C and resistors R, capacitor C ₂ and resistor R ₂ are high-frequency correction circuits, capacitor C ₁ and resistor R ₁ are mid-range correction circuits, and capacitors C ₃ and C ₄ and resistors are R ₃ constitutes a low frequency correction circuit. Then, each of these correction circuits functions to adjust the phase characteristics in continuous frequencies. These high-pass filter and low-pass filter are used as passive elements, they are connected to each other, and one end of the low-pass filter is grounded. If only one side of the circuit of FIG. 1 is illustrated, it is equivalently shown as in FIG.

In the equalizer circuit of this example, it is very important to determine the constants of the constituent elements.

Specifically, it is ideal that the resonance frequency in the room that serves as the sound field or the vehicle interior is substantially matched. But,
In the equalizer circuit of the present embodiment, the changes in the phase characteristics and the frequency characteristics are very smooth, so it is not necessary to make strict settings. The phase characteristics should be delayed in the frequency band of about 1 KHz or less, and the level should increase as the frequency decreases. By doing so, the sense of localization in the left-right direction is improved, and the sound has a solemn feeling. In the frequency band of the extent or 5KH _z than about 1 KHz, while as the phase characteristic becomes proceeds Gimi, so that the frequency characteristic levels rise.
By doing so, the sense of localization in the front-back direction is improved. Frequency band around 5KH _z from 12KH _z are the frequency band influencing the music of the richness, the same characteristics as described above, that is, with so that the phase characteristic becomes proceeds Gimi, frequency characteristics Try to rise. 12KH _z
The above frequency band is an important frequency region for improving the atmosphere and producing a more natural sound, and is also a region necessary for eliminating the psychological oppressive feeling that restrains the head. Further, in the vicinity of about 1 KHz, a peak inverse characteristic of the resonance frequency of the reproduced sound field (for example, the passenger compartment) is set. Therefore, it is necessary to use a constant that satisfies the characteristics required for each of these frequency bands. An example of this characteristic is shown in FIG. The characteristics required for each frequency band described above are satisfied.

In addition, in order to emphasize the phase correction and to correct the frequency characteristic, the equalizer circuit may use an inductor L ₂ as a part thereof, as shown equivalently on one side in FIG. . In this example, the inductor L ₂ is used for high frequency phase correction (enhancement). However, in this case, it is necessary to bring the resonance frequency due to the relationship between the inductor and each element of the circuit to outside the used frequency band.

Since various equalizer circuits shown in this embodiment are open loop circuits that are very simply configured, unlike conventional complicated circuits in which filters having various characteristics are serially connected, phase equalization It has a characteristic that even if a percussion instrument with a very small dynamic range and a large dynamic range that produces an instant sound is played back, there is no sound deviation. Then, as a result of actually operating the equalizer circuit of the present invention, if the characteristics in the psychological aspect that cannot be measured by the measuring device are described in detail, the following can be said. (A) Phase distortion is reduced, For example, even when reproducing sounds with the same frequency but different qualities, the sense of localization of the sound image is improved to a greater extent than before.

Specifically, for example, even when the sound of the violin and the sound of the piano emit the sound of the same frequency at the same time, the mutual positional relationship (front and rear, left and right) between the violin and the piano becomes very clear.

(B) The sound becomes very clear. In other words, it feels like the curtain is off. This is natural because the phase distortion is reduced. Specifically, the sound of striking a string or the sound of rubbing can be heard well.

(C) The sound becomes realistic. More specifically, it feels as if you are on the side of the speaker or performer. This is considered to be a synergistic effect due to improved localization.
To make this sense of reality even more specific, a nearby sound source is located in front of (close to) the speaker, a distant sound source is located farther than the speaker, and in the left-right direction, the azimuth angle of the speaker. Wider or narrower, reproduce the azimuth angle of each sound source. In other words, it is closer to the image of reproduction of the original sound field than the image of reproduction of the original sound.

(D) The sound did not get tired even after listening for a long time. It is considered that this is because the phase distortion remarkably decreased and the sound became closer to a natural sound. This psychological effect is especially important in car audio.

(E) Even when I listened to it in the passenger compartment, I felt as if I was listening to it in a large hall, and I no longer had the oppressive feeling of holding my head down. It is considered that this is because the localization feeling is improved due to the level up of the frequency band of 12 KHz or more and the phase advance, and the position of the sound image is clear.

(F) By adjusting the volume with the volume adjuster (volume), the entire sound image sounds like approaching or moving away. Specifically, lowering the volume will make you feel as if you are playing far away, and increasing it will make you feel that you are playing closer.

(G) The so-called flicker noise at the output saturation of the latter-stage connected amplifier is reduced, but it is completely eliminated.

As described above, in this embodiment, each filter has one
Although the one formed by the resistor and the capacitor is illustrated as an example, the equalizer circuit is not limited to this, and if an equivalent circuit is formed, an equalizer circuit formed by a complicated circuit that results in the circuit of this embodiment ( Needless to say, for example, π-type connection) may be used. Further, the equalizer circuit of this embodiment is of course applicable to various amplifiers such as an audio amplifier normally used indoors and an audio amplifier mounted in a passenger car.

[Effects of the Invention] As is clear from the above description, according to the equalizer circuit of the present invention, phase distortion can be eliminated, and more natural sound can be obtained.

Also, it has never been used in audio circuits such as home stereos, CD players, record players, tape players, FM receivers (audio after FM detection), TV receivers (audio after FM detection), and loudspeakers. I was able to play a good sound (the original sound field). I was able to listen to FM and AM car radios without feeling tired, as if I was in a broadcasting studio or a performance hall in the car, without any problems while driving.

[Brief description of drawings]

FIG. 1 is a block diagram of an equalizer circuit according to the present invention, and FIG.
FIG. 1 is a block diagram of only one side of the equalizer circuit shown in FIG. 1, FIG. 3 is a characteristic diagram of the equalizer circuit according to the present invention, and FIG. 4 shows another example of the equalizer circuit only on one side. Block diagram, FIG. 5 is a schematic block diagram of one filter constituting a conventional equalizer circuit, FIGS. 6 and 7 are specific circuit diagrams of the filter circuit shown in FIG. 5, and FIG. 8A. And FIG. 8B is a schematic diagram showing a configuration of a conventional equalizer circuit, and FIG. 9 is a characteristic diagram of the conventional equalizer circuit. R ₁ , C ₁ : Mid-range correction circuit, R ₂ , C ₂ , L ₂ : High range correction circuit, C ₃ , C ₄ , R ₃ : Low range correction circuit.

Claims (1)

[Claims] Claim: What is claimed is: 1. An equalizer circuit for correcting the sound quality and frequency characteristics of a reproduced sound in a variety of sound fields so that the reproduced sound can be reproduced in a state close to the original sound. In the above, the input audio signal has a characteristic that the phase advances as the frequency of the audio signal becomes higher, and the phase of the frequency of about 1 KHz to 5 KHz is advanced relatively in order to give perspective. In the mid-range correction and high-range correction circuits in which resistors and capacitors are connected in parallel or in series with such circuit constants, and in the frequency range lower than about 1 KHz, the phase of the input audio signal is A resistor and a capacitor are connected in parallel that have characteristics such that they become delayed as the frequency of the audio signal decreases, and that they have circuit constants that are the characteristics opposite to the peak of the resonance frequency of the reproduced sound field. There are made low-frequency correction circuit connected in series are interconnected by respective correction circuits, equalizer circuit, characterized in that passively adjust the phase characteristics between the successive frequencies.