Bookshelf speaker bluetooth speaker series audio pro addon power rating 110 watt system 2 way system principle active frequency response 45 25000 hz impedance 4 ohm crossover frequency 2800 hz amplifier type digital housing surface veneer function streaming control feature bluetooth pairing speaker enclosure bass reflex number of tweeters 1 number of midbass drivers 1 analogue input 35mm jack line in digital inputs digital optical other c