turntable speed control

Let me clarify if I may.  The potential slightly fast speed of a "warmed up" turntable is caused by BOTH the belt and bearing.  As the table is used the belt becomes slightly more pliable.  In some bearing designs this allows the bearing to more precisely align itself and work as it was designed.  The "cold" stiffer belt pulls on the platter harder which can create a chaotic situation in the bearing and reduce its performance.  My turntables avoid this, however I have measured this increase in speed myself, in some designs.  My tables btw, often use the Phoenix controllers and they are excellent and great value.  Drift on my tables, with Phoenix controllers is essentially non existent.

Bruce
Anvil Turntables

Hi again. My favorite? Surgical silk thread with a light application of instrument string rosin ( applied while table is spinning ). Sounds best and you also feel very cool when your finished. I also like light test fishing line although its a little noisy on the platter and the knot makes a little ticking sound ( which I have not heard through playback). Belt circumference  affects speed so you need a variable controller.
Why not rubber? Rubber belts get micro tears in them ( meaning pliancy is all over the place) and along with wear can really mess up your W&F. The more friction you have in your bearing the more pronounced this is.

Rubber belts have a bigger "fatter" sound, and less pliable belts tend to sound "crisper" and cleaner, generally throughout the frequency range.
Hope this helps.

Bruce