Subwoofer compensation circuit

This circuit is suitable for closed subwoofer speakers, or inverted speakers. Its boosted frequency range is 30 to
200Hz and can be adjusted. Figure 9-73 is the circuit schematic. The signal
    output by the front stage passes through a buffer filter composed of ICl-a and ICl-b to filter out signals above 300№, and is sent to ICl-c for mixing and then enters the high-pass filter composed of ICl-d. The filter boosts signals in the ultra-low frequency bands . The frequency of its promotion can be adjusted by RP [. The Q value of the filter is determined by the ratio of R13 and R12, which is generally around 0.8. It can be determined based on the total Q value of the speaker and the listening effect.     The power amplifier connected after this circuit can be LM3886, the selected speaker can be 8 inches in diameter, and the resonant frequency of the cabinet should be lower than 60Hz. Carefully adjust the RPi during use of the circuit, and select the Q value of the circuit according to the actual situation to achieve the best sound effect.