Aaarrrggghhh. You’ve done it again, DDrive. Stop already with the "motor vibrations going up into the spindle". This is not really a problem with a direct-drive turntable. As I mentioned on the other thread, DDs are subject to bearing noise, just like any other type of turntable, and to EMI because the motor is close to the platter surface and thus relatively close to the transducer itself, compared to a belt-drive and some (not all) idlers. But DD's are not much subject to mechanical vibrations due to the motor, unless via a circuitous route via the chassis transmission of vibrations that in turn might reach the bearing. The motor when producing torque also exerts a force on the chassis, opposite in direction to the force on the platter, which is why, maybe, DD's sound best with rather massive chassis'.
I also took a look at the Arche website; in my opinion, that platter mat is designed for belt-drive turntables, wherein motor vibration CAN in fact be transmitted into the platter via the belt making contact with the rim. The most it can do for a DD turntable is to improve isolation of the LP from bearing noise or vibration, if that is a problem. I guess also that by the mere fact of elevating the LP further away from the motor, it might also diminish any EMI effects from the motor. Perhaps this has something to do with why it sounds very good on your turntable. However, I do not detect that EMI is a problem with my SP10 Mk3, although I have never measured the field strength at the platter surface. As you know, the Mk3 platter is quite thick and constructed of alu, stainless, and what I think is brass or bronze, all of which make for a pretty good EMI shielding effect.
I can’t resist correcting Dover, because the opportunity to do so is rare. The force that keeps a body in orbit is by convention referred to as a "centripetal force", because it is literally "center-seeking". Think about a biblical type of sling shot. When you spin it around over your head, you are applying a force that keeps the projectile in the sling from flying off in a straight line tangent to the orbit. That force has a vector direction toward the center of rotation, your hand. I actually do not know where we got the term "centrifugal", but it is clearly a misnomer. What we think of as centrifugal force is really inertia, the tendency of a body in motion to continue in motion in a straight line, unless acted upon by an outside force. Inertia is observed as the result of the absence of a force. Centripetal force is applied via the sling to counter-act the inertia of the stone or other projectile in the pocket of the sling.
