Active subwoofer

EE 28 March 1986 Technical characteristics System: Net volume: Crossover network: Frequency range: Recommended amplifier output: Maximum sound pressure: Sensitivity: active closed box 85 litres electronic; 24 dB/octave; Besse! filter 30-100 Hz (see Fig. lb) 50-100 W >100 dB (50-100 Hz) 87.5 dB (1 watt at 1 metre) The subwoofer described in this article can be used to extend any existing loudspeaker system. It has been designed to obtain a frequency response within .±1 dB over the frequency range 30-100 Hz with an enclosure volume of only 85 litres ACTIVE SUBWOOFER The faithful reproduction of very low audio frequencies in normal living rooms poses a number of problems. The first is that the lowest frequency, f, that can be reproduced depends on the length, 1, of the room: f=c/21 [Hz] where c is the velocity of sound waves in metres per second at nor- mal atmospheric pressure and at 20 °C. In a 6-metre long room, therefore, the lowest frequency that can be reproduced without dist...