JPH02168799A - Speaker non-linear distortion prevention device - Google Patents

Abstract

PURPOSE:To prevent the generation of non-linear distortion during a large output by providing a filter circuit, an attenuator, a subtractor, an attenuator adjustment circuit and an amplifier output calculator and adjusting a signal level only when the input voltage of a speaker goes to the level generating the non-linear distortion or above. CONSTITUTION:The output signal of the amplifier output detection circuit 10 of the amplifier output calculation circuit is inputted into a speaker non-linear distortion level detection circuit 8 together with the output signal of a speaker non-linear distortion level input circuit 7. The speaker non-linear distortion level detection circuit 8 compares two pieces of information and sends a control signal to attenuators 5a-5b. When a signal from the amplifier output calculation circuit 10 exceeds the signal being set through the speaker non-linear distortion level input circuit 7, an attenuator control voltage is generated and the attenuation quantity of the attenuators 5a-5b is adjusted. Thus, the output of the adjusted attenuators 5a-5b is subtracted from an input signal by a subtractor 6. Consequently, the non-linear distortion of the speaker can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speaker nonlinear distortion prevention device that prevents nonlinear distortion of a speaker caused by an input signal by subtracting a signal band-limited by a filter circuit from the input signal. It is something.

BACKGROUND OF THE INVENTION Conventionally, there have been many speakers such as pack-loaded horn speakers that utilize acoustic tubes. By the way, in such a speaker, there is a region where the acoustic impedance is small, so the amplitude becomes too large and nonlinear distortion occurs. Conventionally, the only way to prevent this is to use a graphic equalizer to adjust the level in the region where the acoustic impedance is small, or to use a level that does not cause nonlinear distortion.

Problems to be Solved by the Invention However, in the configuration using the tally equalizer as described above, level adjustment by the graph equalizer 1 riser is performed even for signals below the level at which nonlinear distortion occurs. Furthermore, if a graphic equalizer is not used, there is a problem in that it can only be used at a level below the level at which nonlinear distortion occurs, making it impossible to obtain a large output.

The present invention solves the above problem by adjusting the level of the signal in the frequency band where nonlinear distortion occurs when the input to the speaker exceeds the level that causes nonlinear distortion of the speaker. It is an object of the present invention to provide a speaker nonlinear distortion prevention device that can prevent the occurrence of nonlinear distortion.

Means for Solving the Problems In order to solve the above problems, the speaker nonlinear distortion prevention device of the present invention includes a filter circuit that limits the band of an input signal, an attenuator that adjusts the level of the output of the filter circuit, and a filter that controls the output of the attenuator from the input signal. a subtracter that subtracts the output and uses it as an input to power up the speaker; an amplifier output calculation circuit that calculates the output level of the power amplifier from the output of the subtracter; and a respeaker based on the signal from the amplifier output calculation circuit. The attenuator adjustment circuit determines whether the input applied to the force is at the nonlinear distortion level of the speaker and adjusts the amount of attenuation of the attenuator accordingly.

Effect With the above configuration, the signal in the frequency band where the amplitude of the speaker becomes large is filtered by the filter circuit, the level of the signal is adjusted by the attenuator, and the signal of this attenuator is subtracted from the input signal by the subtracter, thereby increasing the power of the speaker. The attenuation amount of the attenuator is adjusted by determining whether the added subtracted signal is at the nonlinear distortion level of the speaker, thereby limiting the signal in the frequency band where nonlinear distortion occurs, and thereby preventing nonlinear distortion from occurring. To prevent.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a speaker nonlinear distortion prevention device according to an embodiment of the present invention. In Figure 11,
Bandpass filter (hereinafter referred to as BP) connected to input terminal 1
A filter circuit is constituted by a low-pass filter (hereinafter referred to as LPF) 2 and a cut-off frequency input circuit 4 for these BPF2 and LPF3.
PF2 and LPF3 are connected to attenuators 5a and 5b, respectively, and the output signals of attenuators 5a and 5b are subtracted from the signal input from input terminal 1 by subtracter 6.

The attenuator adjustment circuit includes a speaker nonlinear distortion level input circuit 7 and a speaker nonlinear distortion level detection circuit 8 to which the output of the speaker nonlinear distortion level input circuit 7 is input, and the amplifier output calculation circuit includes an amplifier gain input circuit and
It consists of an amplifier output detection circuit 10 to which the output of the amplifier gain input circuit 9 and the output of the subtracter 6 are input.
and speaker 13 are connected. The output signal of the amplifier output detection circuit 10 of the amplifier output measuring circuit is inputted to the speaker nonlinear distortion level detection circuit 8 of the attenuator adjustment circuit together with the output signal of the speaker nonlinear distortion level input circuit i￥87, and the speaker nonlinear distortion level detection circuit 8 The output signal of the level detection circuit 8 is inputted to attenuators 5a and 5b, respectively, to adjust the amount of attenuation of attenuators 5a and 5b.6 FIG. 9 is a system diagram using a speaker nonlinear distortion prevention device. In FIG. 9, 14 is a CD player which is a source, 15 is a preamplifier, and 16 is a speaker nonlinear distortion prevention device, which is connected to the power amplifier 12 and the speaker 13.

Next, its effect will be explained. The input signal from input terminal 1 is applied to subtracter 6, BPF2, and LPF3, respectively. Incidentally, the amplitude frequency characteristics of BPF2 and Ll)F3 are as shown in FIGS. 2 and 3, respectively. Here, f1 to f3 are respective cutoff frequencies.

Here, the nonlinear distortion of the speaker will be explained with reference to the drawings. Nonlinear distortion is particularly a problem with speakers that do not utilize acoustic L:, such as backloaded speakers, so here we will discuss speakers that utilize acoustic tubes. FIG. 4 shows the amplitude frequency characteristics of the above speaker. In a speaker using an acoustic tube, there is a frequency at which the acoustic impedance approaches zero. In Figure 4,
This includes f4 and below and f5 to f6. Therefore, in this frequency band, even if the input applied to the speaker is small, the amplitude will be large. If the amplitude exceeds a certain level, the amplitude becomes too large and nonlinear distortion occurs. In other words, nonlinear distortion occurs at amplitudes greater than 0 in FIG. 4. FIG. 5 shows the relationship between the input power to the speaker and the distortion rate of the speaker output. When the input power exceeds P for signals below f4 or between f5 and f6, nonlinear distortion occurs.

Here, fl in FIG. 2 is matched with F5, F2 is matched with F6, and F3 in FIG. 3 is matched with F4. Also, depending on the speaker 13 to be combined, f4~. Since F6 changes, that information is input to the cutoff frequency input circuit 4, and f1 to f3 are changed.

Next, the signal band-limited by BPF2 and LPF3 is level-adjusted by attenuators 58 to 5b. By the way, as for the method of controlling the attenuators 5a to 5b, first, the gain of the power amplifier 12 to be combined is set by the amplifier gain input circuit 9. The set information is then input to the amplifier output detection circuit. In addition, the output of the subtracter 6, that is, the input signal of the power amplifier 12 is also input to the amplifier output detection circuit 1.
Enter o. The amplifier output detection circuit 10 calculates the output value of the power amplifier 12 from these two signals, and inputs the information to the speaker nonlinear distortion level detection circuit 8. Next, the input level (P in FIG. 5) at which nonlinear distortion occurs in the speakers 3 to be combined is set by the speaker nonlinear distortion level input circuit 7, and that information is also input to the speaker nonlinear distortion level detection circuit 8. Then, the speaker nonlinear distortion level detection circuit 8 compares these two pieces of information and sends a control signal to the attenuators 5a to 5b.

FIG. 6 is a diagram showing the relationship between the input power of the speaker 2 and the control voltage of the attenuator. Amplifier output detection port +'?
The signal from 810 is input to the speaker nonlinear distortion level input.
When the signal does not exceed the signal set by fI7, no attenuator control voltage is generated. Therefore, attenuators 5a to 5b
The amount of attenuation is −ω. Next, when the signal from the amplifier output detection circuit 10 exceeds the signal set by the speaker nonlinear distortion level input circuit 7, that is, when the input power of the speaker 13 exceeds P at which nonlinear distortion occurs, the attenuator control voltage Occurs. In this way, a control voltage is generated according to the input power of the speaker 13, and the attenuators 5a to 5
Adjust the attenuation amount of b.

The outputs of the attenuators 5a to 5b adjusted as described above are subtracted from the input signal by a subtracter 6. FIG. 7 shows the amplitude frequency characteristics of the output signal of the subtracter 6. a
is a signal at a level that does not cause nonlinear distortion of the speaker 13,
b is a signal at a level that begins to occur, and C to d are signals at a level that begins to occur. In this manner, at frequencies below f4 and between f5 and f6, the level at which nonlinear distortion begins to occur is never exceeded. FIG. 8 is a diagram showing this as an amplitude frequency characteristic of the speaker 13.

In this way, according to the present embodiment, the outputs of +31-'l' 2 and I-PF3 are level-adjusted by the attenuators 5a to 5b, and the levels are subtracted from the input signal by the subtracter 6, thereby reducing the nonlinear distortion of the speaker. can be prevented. Furthermore, it is possible to determine whether the input power applied to the speaker 13 is at a level at which nonlinear distortion occurs, based on which signal is used by the speaker nonlinear distortion level detection circuit 8, the amplifier output detection circuit 10, or the speaker nonlinear distortion level input port ii7. , This makes it possible to generate a control voltage according to the input power of the speaker 13. Further, various power amplifiers 12 can be combined with each other through the amplifier cane input circuit 9, and various speakers 13 can be combined with each other through the cut-off frequency input circuit 4 and the speaker nonlinear distortion level input circuit 7.

In this embodiment, B I) F is a filter having a low cut-off frequency and a high cut-off frequency, but it may be a zero-order pair (n is a positive integer) of B P F.

Effects of the Invention As described above, according to the present invention, by providing a filter circuit, an attenuator, a subtracter, an attenuator adjustment circuit, and an amplifier output calculation circuit, the input power of the speaker can be increased to a level that causes nonlinear distortion. By adjusting the level of the signal in the frequency band where nonlinear distortion occurs, it is possible to prevent nonlinear distortion from occurring at high output.

Also, the filter circuit can be BPF or 1. ,, l"F
By doing so, the frequency band to be controlled can be divided. Further, by providing a cut-off frequency input circuit in the filter circuit and a speaker nonlinear distortion level input circuit in the attenuator adjustment circuit, the present invention can be combined with various speakers. By providing an amplifier gain input circuit to the amplifier output calculation circuit, it is possible to realize a number of excellent speaker nonlinear distortion prevention devices that can be combined with various power amplifiers.

[Brief explanation of the drawing]

Fig. 1 shows the configuration of a speaker nonlinear distortion prevention device according to an embodiment of the present invention. The figure is an amplitude frequency characteristic diagram of a speaker using an acoustic tube.
Figure 6 is a speaker input power vs. distortion rate characteristic diagram, Figure 6 is a speaker input power vs. attenuator control voltage characteristic diagram, Figure 7 is an amplitude frequency characteristic diagram at the output of the speaker nonlinear distortion prevention device, and Figure 8 is a speaker nonlinear distortion prevention device diagram. FIG. 9 is a block diagram showing a system configuration using the speaker nonlinear distortion prevention device. 1...Input terminal, 2...BPF, 3...LPF,
4... Cutoff frequency input circuit, 5a-5b... Attenuator, 6... Subtractor, 7... Speaker nonlinear distortion level input circuit, 8... Speaker nonlinear distortion level detection circuit, 9... Amplifier gain input circuit, 10... Amplifier output detection circuit, 11... Output terminal, 12... Power amplifier, 13... Speaker. Agent Yoshihiro Morimoto β1 Yang [Rainbow-Ill,,< niY (9A) Snore lσ (8A) Shiba Imitation

Claims (1)

[Claims] 1. A filter circuit that limits the band of an input signal, an attenuator that adjusts the level of the output of the filter circuit, and a subtracter that subtracts the output of the attenuator from the input signal and inputs it to the power amplifier of the speaker. and an amplifier output calculation circuit that calculates the output level of the power amplifier from the output of the subtracter, and a signal from the amplifier output calculation circuit that determines whether the input applied to the speaker is at the nonlinear region level of the speaker. and an attenuator adjustment circuit that adjusts the amount of attenuation of the attenuator. 2. The filter circuit includes at least one of a band pass filter that passes only a certain frequency band and a low pass filter that passes only a low frequency band, and a cutoff frequency of at least one of the band pass filter and the low pass filter. 2. The speaker nonlinear distortion prevention device according to claim 1, further comprising a cut-off frequency input circuit. 3. The amplifier output calculation circuit includes an amplifier gain input circuit that sets the gain of the power amplifier, and an amplifier output detection circuit that detects the output value of the power amplifier based on the output of the subtracter and the output of the amplifier gain input circuit. 2. The speaker nonlinear distortion prevention device according to item 1. 4. The attenuator adjustment circuit includes a speaker nonlinear distortion level input circuit that sets the speaker nonlinear distortion level, and a signal from the amplifier output calculation circuit and the speaker nonlinear distortion level input circuit to adjust the output of the power amplifier to the speaker nonlinear distortion level. 2. The speaker nonlinear distortion prevention device according to claim 1, further comprising a speaker nonlinear distortion level detection circuit that determines whether the nonlinear distortion level is at a certain level and applies a control signal corresponding to the level to the attenuator when the nonlinear distortion level is exceeded.