Pa subwoofer principle passive woofer size 18 inch design 1 way system speaker lf 1x 18 dimensions 550 x 680 x 475 mm weight 26 kg power rating rms 600 watts power handling peak 1 200 watt noise level 94 db impedance 8 ohm frequency response 35 3500 hz types of connection 6 35mm trs screw terminal speakon case material bass reflex