Bookshelf speaker power rating 80 watt effective output 130 watt system 2 way system principle passive frequency response 80 20000 hz sensitivity 87 dbmw crossover frequency 2500 hz power supply passive cabinet surface ash speaker enclosure bass reflex number of tweeters 1 treble chassis 25 mm tweeter material tweeter tissue number of midbass drivers 1 bassmidtone chassis 102 mm midbass driver material woofer midrange aluminium bass reflex