Above photo: TAD Spotmat #8
So what's the purpose of a platter mat anyway...?
Should it merely be a cushy pad for the record to lie against while being played...? If so, why...? Explain that.
Should it serve to grip both the record and the platter surfaces in order to prevent record slippage...?
Should it serve to isolate the record from low frequency bearing-rumble coming up off the platter...?
Should it serve to damp resonance coming off the record as the record reacts to the stylus vibrating in the groove...?
Should the record be tightly coupled to the platter mat surface...?
Should the platter mat serve to de-couple the record from the platter, ...and even from the platter mat... as much as is possible...?
Should the platter mat react to resonant energy coming off the record and re-direct this energy into itself or allow the resonance to dissipate into air...?
Should the platter mat react to resonant energy coming off the record by re-directing this energy back into the record, into the stylus..?
Should it serve to conduct static electricity....? To not conduct static electricity...? To ground static electricity to the spindle...?
What if....you didn't use a platter mat?
Dampen: Websters Dictionary def: To check or diminish vigor or activity.....
In the audio world, the term dampen is used in combination with terms like resonance and vibration. As in to dampen unwanted resonance.
Isolate: Websters Dictionary def: To keep by itself; separate from others.....
In the audio world, the term isolate is used in combination with terms like acoustic resonance, resonance and vibrations. As in to isolate from unwanted acoustic resonance.
For this page I would like to examine different approaches commonly employed when designing the platter to record interface.
1) Record resonance's are absorbed into the platter mat through a tightly coupled fit between mat and record. The intent is to duplicate as closely as is possible the conditions under which the original master disc was cut. Rigidity is the key ingredient. Typically some type of clamping or weighting and curving force from above the record is employed to assist in the coupling. Mat construction is of a material designed to damp and dissipate resonant energy. Or maybe the record is coupled to the bare platter surface. In this case, the platter mass is intended to be enough to dampen resonant energy off the record and from the bearing.
2) The record lies upon a soft flat pad. The pad, known as a platter mat, serves to cushion the record, provide grip and will offer some vibration damping between record and the platter bearing. This type of mat may be used with or without a record clamp.
3) Record is decoupled as much as is possible from the record player by limiting areas of contact between platter and mat and, with some, between mat and record. This will include a volume of air under the record. Record resonance's may be transmitted into this mat and dissipated or they may by design be allowed to dissipate in air. Isolation is an important ingredient in this scheme. This type of mat typically can not be used with a record clamp.
An example of category 1:
Direct Coupling between bare platter and the Lp.
Above thumbnails, a Teres screw-down clamping system. With the hard delrin spacer located under the record, it raises the record slightly above the surface level of the bare platter. The outer face of the clamp, as it is screwed down on top of the record forces the record to curve downward in a gentle parabola until the soft vinyl makes contact with the platter, who's shape it conforms to. A typical result is a coupling between record and platter so efficient that a slight vacuum is noticed when removing the record from this player.
DIY "None-Felt" mat: cheap and easy to make.
Cork / leather mat. Here's one that works nicely
Cork / felt mat
Ringmat just pictures so far. More to come
Spotmat: review and analysis