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Crossover For Subwoofer
Since the bass information is present in both (stereo) loudspeakers, the signal for the sub woofer can simply be tapped from one of them. The network is a 1st order low-pass filter with variable input (P1) and presettable cut-off frequency (P2). The signal from the loudspeaker is applied to terminal ‘LSP’. Voltage divider R1-R2-P1 is designed for use with the output signal of an average output amplifier of around d 50 W. The crossover frequency of the network may be varied between 50 Hz and 160 Hz with P2. The values of R3, P2, and C1, are calculated on the assumption that the subwoofer amplifier to be connected to K1 has a standard input resistance of 47 kΩ.
If this figure is lower, the value of C1 will need to be increased slightly. It is advisable to open the volume of the subwoofer amplifier fully and adjust the sound level with P1. This ensures that the input of the subwoofer amplifier cannot be overloaded or damaged. Make sure that the ground of the loudspeaker signal line is linked to the ground of the subwoofer amplifier. If phase reversal is required, this is best done by reversing the wires to the subwoofer. If notwithstanding the above additional protection is desired at the input of the subwoofer amplifier, this is best effected by ‘overload protection ’ elsewhere in this site.