Pa sound system principles active passive woofer size 8 inch design 2 way system construction bi amping speakers lf 1x 8 hf 1x dimensions 510 x 310 x 245 mm weight 15 kg power handling peak 600 watt noise level 123 db impedance 8 ohm frequency response 50 20000 hz connections sd card microphone usb types of connection rcacinch stereo clamp contacts usb case material bass reflex