Active speaker pa sound system principle active woofer size 8 inch construction bi amping speaker lf 1x 8 dimensions 245 x 292 x 476 mm weight 102 kg power handling peak 400 watt noise level 121 db impedance 8 ohm frequency response 50 20000 hz connections sd card microphone usb types of connection rcacinch stereo usb case material bass reflex