'From a functional, aesthetic and sound quality perspective, Rega considers pure wool is ideal empirically speaking, but it does suffer from numerous problems in static generation and physical stability which have cost penalties. (If cost is irrelevant, a felt mat will consist of at least three kinds of wool fibres, plus a few strands of synthetic fibre, multi layered at different angles, and pre shrunk two or three times before die cutting to the required shape.'
'A reviewer once questioned the validity of Rega using an ultra-stiff platter beneath a soft felt mat - superficially a not unreasonable question. However, he had failed to realise that the platter and mat have entirely different functions: the platter behaves as a flywheel, gyroscope, and becomes the source of stable energy needed by the disc; the mat requirement is that of an ideal interface in transferring this rotational energy into the vinyl disc. Because the surface area of contact is very large (up to 700 square centimetres), and relatively thin, a low level of friction still couples the disc to the platter with zero slippage. Although one square centimetre of contact would allow some horizontal or vertical flexibility, 700 effectively becomes rigid - much more so than the vinyl itself.
Taken from the Rega book 'A Vibration Measuring Machine' (pages 221/2).