Loudspeakers

Developed by PS Audio's Senior Loudspeaker Design Engineer, Chris Brunhaven, the aspen range's planar magnetic (PM) mid and treble drivers are core to the performance and sound of this speaker family. PM drivers are attractive for any number of reasons but principally for the elegance of a single, directly driven diaphragm with no translational components. A conventional driver will include a voice-coil former, spider/suspension, dustcap/phase plug, cone and surround, etc, that can all contribute to resonances and reflections, the latter from mistermination at the various mechanical boundaries. Planar diaphragms are also very light – 12µm Teonex here – while the 'voice coil' is nothing more than a few turns of 17µm etched aluminium on the surface with, again here, a reversed turn at the outer edge for damping. The low sensitivity of earlier PM drivers is countered with powerful neodymium magnets but the precise corrugation, clamping and damping of the diaphragm is also key – ensuring the film responds in a uniform and predictable fashion is the biggest obstacle faced by any designer lured by the potential of PM driver technology.

The main components – but not all the detail – of PS Audio's PM drivers are illustrated in the rendering showing, from front to back (left to right), a perforated 1.5mm low-carbon steel pole plate; N52 NEO magnets (15 pieces of 3x5x50mm, but the FR10 tweeter has three rows and the midrange seven rows vs. the five rows shown here); and an acoustically resistive scrim cloth and wool felt strip. The thin-film diaphragm lies at the centre, with cloth/magnet/pole piece behind, terminating in a polycarbonate rear chamber filled with polyester/wool and Twaron fibre for acoustic loading and damping of the back wave. PM