Bookshelf speaker series dali zensor system 2 way system principle passive frequency response 50 26500 hz sensitivity 88 dbmw noise level 108 db impedance 6 ohm crossover frequency 2600 hz recommended amplifier power 25 125 power supply passive colour black cabinet surface ash housing surface veneer vinyl speaker enclosure bass reflex number of tweeters 1 treble chassis 25 mm tweeter material tweeter tissue number of midbass drivers