Subwoofer Filter Circuit
This is a circuit of subwoofer active filter circuit is a 24 dB octave filter with a Bessel character and cutoff frequency of 200 Hz. So, if you are interested in experimenting with audio circuits in subwoofer range, this circuit is for you. This is the figure of the circuit;
In subwoofer range, all audio frequencies below 200 Hz can be fed to a single speaker box since the human directional perception of sound diminishes at this frequency range. The normal stereo signals above 200 Hz can be fed to two satellite speaker boxes. How does the subwoofer filter works: A1 and A2 buffer the signals coming from right and left channels. Op amp combinations A2/A4 and A9/A10 function as the high pass filters. The outputs are then connected to the final amplifiers of the battelite boxes. Signals from both channels are fed to A5. Op amps A6/A7 function as the low pass filter, A8 as the output amplifier for the subwoofer signal.
The signal level can be balanced between the subwoofer and the satellite lines. The power needed for this filter circuit must ne a symmetrical power supply. The op amps can have either JFET or bipolar inputs.