The loudspeaker in question is the new d&b B4-SUB, ostensibly a cardioid sub and the new addition to d&b's extensive subwoofer collection. "But this one is very different," said Taylor. "Matthias Christner from the R&D acoustics department refers to it as PSP (as opposed to DSP) which stands for Plywood Signal Processing!
"DSP is normally needed to create the necessary phase shift over frequency required by the cardioid sub design, which of course needs its own dedicated amp channel. To do that in the passive domain, which is simply through cabinet design, has long been dismissed as improbable. Essentially Matthias has used a band pass cabinet design coupled with unique driver characteristics and some unusual porting to replicate acoustically what would normally be done in the electronic domain using DSP.
"Why is such an apparently odd loudspeaker design desirable? In a word, size. Most cardioid subs are either very large, or need three cabinets close stacked in opposition. The B4 is not only small and performs in isolation in a cardioid manner, it is also power lean; that is you can drive eight B4s off just two of d&b's D6 or D12 amplifiers, the cardioid amp channel not being needed, which paves the way to small distributed bass arrays, even in a proscenium arch theatre. That's a double benefit, cardioid performance keeping low frequencies off the stage, and arrayed bass providing a far more even coverage across the audience."
(Jim Evans)
