Back then the approach used a combination of stacking standard loudspeakers with specific amplifier configurations, which proved both effective and consistent and was followed by the introduction of both the J-SUB and J-INFRA cardioid subwoofers, using front and rear radiating drivers powered by separate amplifier channels. In 2008 d&b perfected and patented the 'Loudspeaker system with reduced rear sound radiation' which in turn led to the development of the B4 subwoofer. Being the first utilisation of this patented technique, the B4-SUB is really quite unique.

The B4-SUB enclosure houses two long excursion neodymium drivers: a15" driver in bass-reflex design facing to the front and a 12" driver in a two chamber bandpass design radiating to the rear. The design reduces unwanted level behind the cabinet by more than 15dB over its entire operating bandwidth and provides the highest accuracy in low frequency reproduction extending from 40 Hz to 150/100 Hz.

Each channel of a d&b D6 or D12 amplifier drives up to two loudspeakers with the B4-SUB configuration selected. The B4-SUB is specifically designed for ground stack use only; an M20 threaded flange in the top panel accepts a loudspeaker stand, while two runners extend from front to rear of the bottom panel and fit to correspondingly shaped recesses in the top to greatly aid stacking. Weighing 44kg (97lb), producing 128dB SPL and 131dB SPL when driven with the D6 and D12 respectively, the cabinet has a pair of handles, four wheels on the rear and an optional transport lid all in an enclosure measuring 476mm (18.74") x 580mm (22.84") x 800mm (31.6").

The B4-SUB may be integrated into setups consisting of d&b's latest T-Series or E-Series loudspeaker systems. It is complimented by a variety of mounting accessories for these loudspeaker Series matching them acoustically as well as providing a solid physical base for stacking. Firmware and software updates that include the B4-SUB are available for download under the relevant sections within Support/Downloads at www.dbaudio.com. These provide B4-SUB configurations for all current d&b amplifiers and R1 Remote control software V1.8 which also supports this subwoofer. For the first time, this highly economic medium sized subwoofer delivers the huge acoustical advantage of cardioid behaviour into another level of reinforcement systems.

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