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 arrangement avoids unwanted energy behind the system that greatly reduces the excitation of 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 configuration.
 

The B4-SUB cabinet is constructed from marine plywood and 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 front of the loudspeaker cabinet is protected by a rigid metal grill in front of an acoustically transparent foam. Two runners extend from the rear to the front panel of the cabinet protecting the bottom panel against scratching.Two correspondingly shaped recesses are incorporated in the top panel of each cabinet that accept these runners to prevent cabinet movement when stacked. Mounted on the rear panel are four heavy duty wheels.