Bookshelf speaker series elac debut power rating 50 watt effective output 70 watt system 2 way system speaker system 20 stereo principle passive frequency response 44 20000 hz sensitivity 87 dbmw impedances 4 6 8 ohm crossover frequency 3000 hz recommended amplifier power 20 120 power supply passive colour black front colour black housing material mdf enclosure speaker enclosure bass reflex number of tweeters 1 treble chassis 25 mm