The Thunder-KS3P I is a compact passive subwoofer featuring a long excursion 21” neodimium magnet woofer with 4” voice coil. The Thunder-KS3P 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.