Floor speaker series elac debut power rating 55 watt effective output 140 watt system 25 way system principle passive frequency response 42 20000 hz sensitivity 87 dbmw impedances 4 6 8 ohm crossover frequencies 200 3000 hz recommended amplifier power 20 140 power supply passive colour black front colour black housing surface veneer vinyl housing material mdf enclosure design down firing subwoofer speaker enclosure bass reflex nu