JPH0787632B2 - In-vehicle low frequency correction device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted reduction correction device that improves the acoustic characteristics of a passenger compartment of an automobile.

2. Description of the Related Art In recent years, in-vehicle low-frequency correction devices are mainly used as a speaker system for low-frequency reproduction that is effective in improving the acoustic characteristics in the passenger compartment, but in combination with conventional reproduction devices without correction devices. The present situation is that the fine adjustment of the reproduction frequency band so as to be adapted to the vehicle interior spaces having different shapes and shapes is not made in the configuration.

A conventional vehicle-mounted low-frequency correction device will be described below.

FIG. 7 shows a low frequency reproduction system as an example of a conventional vehicle-mounted low frequency correction device. Reference numeral 1 is a reproducing device such as a car radio, a car tape deck, a car compact disc player, 2 is a mixing circuit, 3 is a band pass filter, 4 is an amplifier, and 5 is a speaker.

FIG. 8 shows the amplitude characteristic of the bandpass filter 3 described in FIG.

Regarding the vehicle-mounted low-frequency correction device configured as described above,
The operation will be described below.

First, the right and left signals sent from the playback device 1 are mixed by the mixing circuit 2, limited by the bandpass filter 3 to low-frequency sounds centered at a frequency of 50 to 100 Hz, and amplified by the amplitude unit 4. And reproduced by the speaker 5. As a result, the low-frequency sound that was insufficient only with the reproduction device without the low-frequency correction device is increased in sound pressure because the reproduction sound from the speaker 5 is added, and is balanced with the mid-high range sound and is flat in the vehicle interior to the low range. The pressure frequency characteristic is obtained.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-described conventional configuration, since the characteristic of the bandpass filter 3 is such that it becomes symmetrical about the frequency at which the amplitude becomes maximum as shown in FIG.
For example, when the center frequency is set to 60 Hz, the playback sound pressure of 60 Hz increases, but even if you try to raise the sound pressure of 150 Hz or more included in the musical instrument base by 1 dB to 2 dB, only a specific frequency other than the above center frequency (60 Hz) The sound pressure cannot be increased, and the sound pressure rises over the entire reproduction frequency band of the bandpass filter 3. As a result, the sound pressure rises to an unnecessary frequency. It will not change. Also, on the acoustic characteristics of the interior of the car, when the center frequency is set to 60 Hz, even if you try to raise the sound pressure near 200 Hz, which is buried in the road noise of the car, by a few more dB, the same result as above, Asymmetrical amplitude characteristics or frequency characteristics capable of increasing only the reproduced sound pressure at the target plural frequencies have not been obtained.

As described above, the current low-pass correction device having the configuration using the bandpass filter 3 has a drawback that effective correction cannot be performed.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a vehicle-mounted low-frequency correction device having an asymmetrical amplitude characteristic.

Means for Solving the Problems In order to achieve this object, an in-vehicle low-frequency correction device of the present invention comprises a mixing circuit for mixing a signal from a reproduction device, a high-pass filter of at least a second order or higher, and a low-pass filter in series. A configuration in which a bandpass filter configured to be connected and limiting the low-frequency reproduction frequency band of the output signal of the mixing circuit, an amplifier that amplifies the signal from the handpass filter, and a speaker that reproduces the signal from the amplifier It is what

Operation With this configuration, we realize a bandpass filter with an asymmetrical amplitude characteristic that can improve only the reproduced sound pressure at the target multiple frequencies, and obtain excellent sound pressure frequency characteristics. You can

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the structure of a vehicle-mounted low-frequency correction device according to an embodiment of the present invention. In FIG. 1, 6 is a reproducing device such as a car radio, a car tape deck, and a car compact disc player, 7 is a mixing circuit, 8 is at least a high-pass filter of at least second order, 9 is a low-pass filter of at least second order, and 10 is The amplifier 11 is a speaker.

The operation of the vehicle-mounted low-frequency correction device of the present invention configured as described above will be described below.

First, the right and left signals sent from the reproducing device 6 are mixed by the mixing circuit 7, and are mixed by the circuit configuration shown in FIG. 4 and at least a second-order or more high-pass filter 8 having the amplitude characteristic shown in FIG. Ultra low frequencies below 60Hz are cut with a slope of -12dB / octave. The system function of the high pass filter 8 is expressed by the following equation.

However, C ₁ , C ₂ : Capacitor, R ₁ ,, R ₂ ,, R _F , R _S : Resistance, V _i : Input voltage, V
_o : Output voltage Further, the low-frequency cutoff frequency of the high-pass filter 8 and the Q _H of the circuit showing the sharpness of resonance are expressed by the following equations.

Here, when the Q of the circuit is set to 1 or more, as shown in FIG. 2, the amplitude characteristic can have a peak near the low cutoff frequency.

Next, the signal that has passed through the high-pass filter 8 is processed by the circuit configuration shown in FIG. 5 and the low-pass filter 9 of at least second order having the amplitude characteristic shown in FIG.
The above frequencies are cut with a slope of -12 dB / octave. The system function of the low pass filter 9 is expressed by the following equation.

However, S = jw, C ₃ , C ₄ : Capacitor, R ₃ , R ₄ : Resistance, V _X : Input voltage, V _Y : Output voltage Also, the high frequency cutoff frequency of this low pass filter 9 and the circuit Q _L showing the sharpness of resonance. Is expressed by the following equation.

Here, the low pass cutoff frequency of the high pass filter 8 is
60 Hz, as the Q _H of the circuit showing the sharpness of the resonance becomes 3.0, C
₁ = 0.1μF, C ₂ = 0.1μF, R ₁ = 33kΩ, R ₂ = 22kΩ, R _F = 39k
Ω, Rs = 15kΩ and the constants of the capacitor and resistance are set, R ₃ = 47kΩ, R so that the high-pass cutoff frequency of the low-pass filter 9 is 150Hz and the Q _L of the circuit showing the sharpness of resonance is 0.6.
Set ₄ = 47 kΩ, C ₃ = 0.027 μF, C ₄ = 0.018 μF and the constants of the resistor and capacitor.

FIG. 6 shows the amplitude characteristic of the high-pass filter 8, the amplitude characteristic of the low-pass filter 9, and the amplitude characteristic after passing through the high-pass filter 8 and the low-pass filter 9 at this time.

As can be seen by comparing the amplitude characteristic of FIG. 6 with the conventional characteristic shown in FIG. 8, the overall characteristic of FIG. 6 clearly shows an asymmetrical amplitude characteristic or frequency characteristic.
Thus, the overall characteristic of the present invention is that the adjustment of the sound pressure level in the vicinity of 60 Hz and the adjustment of the sound pressure level in the vicinity of 150 Hz to 200 Hz, which is the connecting portion from the vicinity of 60 Hz to the mid-high range, are performed individually and arbitrarily. It is possible to adjust to the sound pressure level of, compared with the conventional symmetrical bandpass filter shown in FIG. 8 at a frequency of 150 Hz or higher.
Amplitude is increased from 1dB to 2dB.

Thus, when a signal having an asymmetrical amplitude characteristic is reproduced by the speaker 11 in addition to the amplifier 10, the maximum amplitude is larger than that of the conventional vehicle-mounted low-frequency correction device having a symmetrical amplitude characteristic. Fine adjustment of sound pressure at frequencies above and above 150Hz, which is important for low frequency sound reproduction, and sound pressure around 200Hz, which is apt to be buried due to vehicle interior characteristics and car road noise, etc., are raised to arbitrary levels. As a result, the sound pressure does not increase over the entire reproduction frequency band including unnecessary frequencies, and only the sound pressure at the required multiple points is increased to increase the bass range. It is possible to obtain an excellent corrected sound pressure frequency characteristic, and it is possible to make the sound natural and easy to hear.

As described above, an asymmetric amplitude characteristic can be obtained by connecting at least a second-order or higher active high-pass filter and an active low-pass filter in series to the filter that limits the frequency band of the signal to be reproduced. A good vehicle interior sound pressure frequency characteristic can be obtained.

In the first embodiment, other constants may be used for the capacitor and the resistor in order to determine the center frequency of the high pass filter 8 and Q _H that indicates the sharpness of resonance. Further, in order to determine the center frequency of the low-pass filter 9 and Q _L indicating the sharpness of resonance, other constants may be used for the resistors and capacitors.

EFFECTS OF THE INVENTION As described above, according to the present invention, the band-pass filter for limiting the low-frequency reproduction frequency band of the signal to be reproduced is configured by connecting at least a second-order or higher high-pass filter and a low-pass filter in series. , It is possible to construct a bandpass filter with an asymmetrical amplitude characteristic that can increase only the sound pressure at the frequencies of the required multiple points. It is possible to realize a vehicle-mounted low-frequency correction device that can obtain characteristics.

[Brief description of drawings]

FIG. 1 is a block diagram of a vehicle-mounted low-frequency correction device according to an embodiment of the present invention, FIG. 2 is an amplitude characteristic diagram of the high-pass filter of FIG. 1, and FIG. 3 is an amplitude characteristic diagram of the low-pass filter of FIG. 4 is an electric circuit diagram of the high pass filter of FIG. 1, FIG. 5 is an electric circuit diagram of the low pass filter of FIG. 1,
FIG. 6 is a general amplitude characteristic diagram of a high-pass filter, a low-pass filter, and a combination of both in the embodiment of the present invention, and FIG. 7 is a block diagram of a conventional vehicle-mounted low-frequency correction device.
FIG. 8 is an amplitude characteristic diagram of the bandpass filter of FIG. 6 ... Reproducing device, 7 ... Mixing circuit, 8 ... High-pass filter, 9 ... Low-pass filter, 10 ... Amplifier,
11 …… Speaker.

Claims (1)

[Claims] 1. A mixing circuit for mixing a signal from a reproducing device which generates an electric signal corresponding to a sound to be reproduced, and a high-pass filter and a low-pass filter of at least a second order or higher, which are connected in series. An in-vehicle low-frequency correction device including a band-pass filter that limits a low-frequency reproduction frequency band of an output signal of a circuit, an amplifier that amplifies a signal from the band-pass filter, and a speaker that reproduces a signal from the amplifier.