Bookshelf speaker series indiana line dj power rating 30 watt effective output 140 watt system 3 way system principle passive frequency response 40 22000 hz sensitivity 93 dbmw impedances 4 6 8 ohm crossover frequencies 500 3500 hz recommended amplifier power 30 140 power supply passive colour black cabinet surface ash housing surface veneer housing material mdf enclosure speaker enclosures bass reflex magnetically shielded removable s