The Thunder-KS4P I is a passive subwoofer featuring 2x long excursion 18” neodimium magnet woofer with 3” voice coil. The Thunder-KS4P I features 2x SpeakON NL4 connectors that allow to input the signals from external active systems or amplifiers, with either a 2-wire or a 4-wire cable, as well as route the signal to other loudspeakers.