The B4-SUB is an actively driven cardioid subwoofer powered by a single amplifier channel. It houses two long excursion neodymium drivers in an integrated cardioid setup: a 15" driver in a bass-reflex design facing to the front and a 12" driver in a two chamber bandpass design radiating to the rear. The cardioid dispersion pattern resulting from this approach avoids unwanted energy behind the system that greatly reduces the reverberant field at low frequencies and provides the greatest accuracy of low frequency reproduction. The B4 subwoofer can only be used in a ground stacked setup. The B4-SUB cabinet is constructed from marine plywood, has an impact and weather resistant paint finish and a pair of handles. An M20 threaded flange in the top panel accepts the d&b Loudspeaker stand winder M20. The loudspeaker cabinet is also available in Special Colour (SC) options.