JPH0722438B2 - Speaker device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker device for general sound reproduction.

Conventional configuration and its problems Conventionally, even if the sound pressure frequency characteristics of the speaker measured in an anechoic room were flat, when the speaker was installed in the actual room, the low-frequency characteristics differed greatly depending on the installation location. . FIG. 1 is a sound pressure frequency characteristic diagram of the speaker according to the installation location of the speaker. In FIG. 1, a is a sound pressure frequency characteristic when the speaker is placed in the air, b is a sound pressure frequency characteristic when the speaker is placed on the floor, and c is a sound pressure frequency characteristic when the speaker is placed in a corner. Show. As can be seen from FIG. 1, the characteristic c when the speaker is placed in a corner and the characteristic a when the speaker is placed in the air differ in sound pressure frequency level in the low frequency range by 10 dB or more. This is because when the speaker is placed near the wall, the radiation impedance increases due to the interaction due to the reflection from the wall in the low frequency range, the efficiency of the speaker also increases, and the sound pressure increases.

Therefore, there is a drawback in that the characteristics of the low frequency range largely change depending on the installation position of the speaker, and the entire reproduced sound sounds different.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a speaker device in which the low frequency sound pressure frequency characteristic is less likely to change regardless of the installation position of the speaker.

According to the present invention, the impedance measurement means for measuring the impedance of the speaker, the storage means for storing the impedance of the speaker at each installation position measured in advance, and the measured value from the impedance measurement means and the stored value are compared. The comparison / determination means and the control means for controlling the correction means for correcting the frequency characteristic according to the content of the comparison are provided, whereby a constant low frequency sound pressure frequency characteristic can be obtained regardless of the installation position of the speaker.

Description of Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows a block diagram of the speaker device in the first embodiment of the present invention. In FIG. 2, 1 is a sound source,
2 is an equalizer for correcting frequency characteristics in the low frequency band, 3 is an oscillator, 4 is an amplifier, 5a and 5b are switches, 6 is a speaker,
Reference numeral 7 is an impedance measuring circuit, and 8 is a microcomputer including a comparison / determination means 9, a storage means 10, and a control means 11.

The operation of the speaker device configured as above will be described.

First, the impedance of the speaker is measured. switch
5a and 5b are connected to the A side, a sine wave is generated from the oscillator 3, passed through the amplifier 4 and reproduced by the speaker 6. A sine wave near the minimum resonance frequency of the speaker is input to the speaker 6, and the impedance at that time is measured by the impedance measuring circuit 7.

FIG. 3 shows a mechanical system equivalent circuit diagram of the speaker. here,
Z _M is the vibration system impedance, Z _ME is the mechanical impedance, M _M is the vibration system mass, S _M is the overall vibration system stiffness,
R _MS is the mechanical resistance of the entire vibration system, M _MA is the radiant mass, and R _MA is the radiative resistance.

Where Z _M and Z _ME are Is represented.

In equation (1), the radiation mass M _MA changes depending on the installation position of the speaker. If the speaker is mounted on the wall, the value will be twice as much as when measured with the speaker placed in the air.
When placed in a corner, it is tripled. The impedance of the equivalent circuit is calculated from equations (1) and (2). Since M _{MA in} equation (3) changes depending on the speaker installation position, the impedance of the equivalent circuit also changes.

On the other hand, if the acoustic power of the speaker is W, the energy density | P | ² becomes Is represented. When a speaker is placed near a wall at a low frequency, which is almost omnidirectional, the radiation space is halved and the directivity coefficient is doubled. That is, since the energy density | P | ^{2 in} equation (4) becomes four times, the sound pressure level is
It will increase by 6 dB. By the same principle, it rises by 12 dB at a place where two surfaces intersect, such as a wall and floor, and by 18 dB at a place where three surfaces intersect.

The impedance and the change in sound pressure level depending on the installation position of the speaker have been described above.

Next, the value measured by the impedance measuring circuit 7 is sent to the comparing and judging means 9. In the comparison judgment means 9,
The impedance value already stored in the storage means 10 is compared to determine the installation position of the speaker.

The storage unit 10 stores the impedance value and the correction coefficient of the frequency characteristic depending on the installation position. When the speaker installation location is determined by the comparison / determination means 9, the control means 11 outputs a control signal for the equalizer 2 to correct the frequency corresponding to the installation location, and sets the frequency characteristic of the equalizer 2.

When the speaker is placed in the air, the boost amount in the low range is increased, and when it is placed in the corner, the boost amount in the low range is reduced.

This completes the speaker device characteristic settings.
5a and 5b are switched to the B side, and the signal from the sound source 1 is reproduced with the frequency characteristic set by the above method.

By correcting the frequency characteristic according to the installation position of the speaker as in the above method, the frequency characteristic can be kept constant.

Next, a second embodiment of the present invention will be described.

FIG. 4 shows a block diagram of a speaker device according to a second embodiment of the present invention. In FIG. 4, the same members as those in FIG. 2 are designated by the same reference numerals. In addition, 12 is a feedback circuit, 13 is a detector, and 14 is an adder.

The operation of the speaker device configured as described above will be described. First, the impedance of the speaker is measured. The switches 5a and 5b are connected to the A side, the impedance is measured in the same manner as in the first embodiment, and the data is sent to the comparing and judging means 9. In the comparison / determination means 9, the speaker installation position is determined by comparing with the impedance at each installation position stored in the storage means 10 in advance. Storage means 10
Also stores the feedback amount corresponding to the installation position, and the control means 11 controls the feedback gain of the feedback circuit 12. Here, a velocity type MFB (motional feedback) method is used, and by increasing the feedback gain, it is possible to lower the low-frequency resonance frequency Q _O and lower the low-frequency sound pressure. Also in
The sound pressure characteristics in the high range can be kept constant. The operation of the simple MFB method will be described below.

As shown in equation (5), Q _O becomes smaller as the feedback gain increases. The sound pressure | Pr | is as shown in equation (6).

That is, the sound pressure | Pr | decreases as the feedback gain increases. When the speaker is placed near the wall, the low range goes up, so the feedback gain of the feedback circuit 12 is increased to reduce the sound pressure in the low range, and when the speaker 6 is installed in the air, the feedback of the feedback circuit 12 is returned. It is possible to reduce the gain and reproduce without reducing the sound pressure in the low frequency range. In this way, by setting the feedback gain according to the impedance change of the speaker depending on the installation position and changing the sound pressure characteristic in the low frequency range, it is possible to keep the low frequency sound pressure frequency characteristic constant regardless of the speaker installation position. Is.

Next, after setting the feedback gain, switch the switches 5a and 5b to B.
To reproduce the signal from the sound source 1. By detecting the speed of the vibration system by the detector 13 and feeding back a voltage proportional to the speed from the feedback circuit 12 to the drive system, distortion is small and the low frequency sound pressure frequency characteristic is constant regardless of the installation position of the speaker. It is possible to keep. Although the speed type MFB method is used in the second embodiment, the same effect can be obtained by using the acceleration type and amplitude type MFB methods.

Advantageous Effects of the Invention According to the present invention, the storage unit stores the impedance value according to the installation position of the speaker, and the comparison determination unit compares the value measured by the impedance measurement circuit with the stored value to determine the installation position, and the control unit. Since the frequency characteristic is controlled by the correction means, the constant frequency characteristic can be always obtained regardless of the installation position of the speaker.

Further, in order to correct the frequency characteristic, a detector for detecting the movement of the speaker vibration system and a feedback circuit whose feedback amount changes according to the output of the control means are provided, and even if the MFB method is performed, not only the same effect as described above is obtained, The distortion can be reduced, and the effect is great.

[Brief description of drawings]

FIG. 1 is a sound pressure frequency characteristic diagram according to a speaker installation position, FIG. 2 is a configuration diagram of a speaker device according to a first embodiment of the present invention, FIG. 3 is a mechanical system equivalent circuit diagram of the speaker, and FIG. It is a block diagram of the speaker apparatus in the 2nd Example of this invention. 2 ... Equalizer, 7 ... Impedance measurement circuit, 8
...... Microcomputer, 9 …… Comparison judgment means, 10 ・ ・ ・
… Memory means, 11 …… Control means, 12 …… Feedback circuit, 13 ……
Detector.

Claims (3)

[Claims] 1. A comparison judgment for comparing impedance measurement means for measuring the impedance of a speaker, storage means for storing the impedance of the speaker at each installation position measured in advance, and the measured value of the impedance measurement means and the stored value. A speaker device comprising: a means and a control means for controlling a correction means for correcting a frequency characteristic according to the contents of comparison. 2. The frequency characteristic is corrected by using an MFB system composed of a detector for detecting the motion of an oscillating system and a feedback circuit whose feedback gain is changed by the control means. The speaker device according to the first section. 3. The speaker device according to claim 1, wherein the correcting means uses an equalizer.