I have pondered just making one
The job of the mat is to control vinyl resonance while the cartridge is tracking the groove, thus preventing the vinyl from talking back to the cartridge. This results in measurably and audibly superior performance.
To do this, the platter pad has to have the same durometer as the vinyl itself.
To know if the pad is doing its job, turn down the volume all the way. Play an LP and listen to the sound emanating from the cartridge itself. If you can hear it from more than a foot away the platter pad is falling short of its goal.
