Hi Fi version
A loudspeaker with two front cavities: one cylindrical & one rectangular
The purpose of this loudspeaker design is to provide a long shallow duct between the diaphragm and the outside world that behaves almost like a pure mass, which lowers the fundamental resonance frequency and therefore extends the bass response, albeit with some sacrifice in sensitivity. A sketch of the loudspeaker is shown in Figure 1. The driver either has a flat diaphragm or conical one with a sheet added to create a planar surface. This radiates sound into the cylindrical cavity which is coupled to the rectangular one by means of an annular ring. Finally, sound is radiated into the outside world through a rectangular outlet slot.
By Tim Mellow of Mellow Acoustics Ltd