Subwoofer series elac debut power rating 100 watt effective output 200 watt system 1 way system principle active frequency response 35 150 hz sensitivity 89 dbmw crossover frequency 50 150 hz power supply mains operation colour black front colour black housing material mdf enclosure controllable via knob toggle switch control features switchable phase control onoff bass level control volume control speaker enclosure bass reflex number of