Subwoofer filter

R25 EE 74 July/August 1986 LE)io cll 180 n -II II 10n 10n (Sat.) ® S1 50mA A2 10n 10n R19 A R21 180 n R2 C11 . 68n R24 C2 481..bwoofer filter TR1 01 D1...D6 = 1N4001 50mA 07 08 101J (D IC1 C21 (DI IC2 C24• maw ? The filter described here is intended primarily for experimenting with a (central) subwoofer (see Active Sub- woofer, EE March 1986, p. 28). As the human ear cannot sense direction in a standing wave, directional sensi- tivity is generally poor at low fre- quencies, so that is would seem superfluous to use a stereo set-up below about 200 Hz. Therefore, the low frequencies can be concen- trated on one good bass enclosure, which, of course, keeps the cost of the overall system down. The satellite loudspeakers (see EE, April 1986, p. 22) will then have to cope with the higher frequencies only. The requisite cross-over network de- scribed here is based on 24 dB/ octave Bessel filters: the cross-over frequency lies around 200 Hz. With reference to the circuit diagram, Ai and...