Belt stretch

Again...

You aren't hearing from other skeptics because your argument is with pure science, not conjecture. Belt creep is a matter of sheer physics; it isn't a theory. That said, there are some very ingenious workarounds for the problem. Frank Schroeder has one that addresses belt creep and implements noise cancellation simultaneously. I heard his turntable at some length, and it works. There are others who offset or minimize the issue in their designs, too. Whatever the drive system, it is the implementation of it that separates the men from the boys.

Doug is also correct in his assertion that rubber deforms. The key to success here is in choosing an optimum footprint, density, pressure, physical configuration, and mass of the rubber, so that it does its job in the least invasive way. This means that the rest of the turntable has to be designed in keeping with that aspect. It can be done, however.

The bottomline, I suppose, is that the type of drive isn't quite as important as the makeup of it, and if that makeup includes slip, there's your first obstacle to overcome.

Mosin, Im not arguing that belt slip exists or that rubber deforms or that there is some theoretical friction from stylus drag. Im questioning the audibility of these conditions and other than "I can hear it" and attributing "it" to the afore mentioned conditions no one yet has demonstrated that this so far unmeasurable speed variation is responsible for the effects they are hearing. If the speed measures stable with a strobe then what pitch related anomaly can be heard? When John hears better bass extension and dynamics with his idler compared to belt but both systems are showing no deviation in speed perhaps its not speed shift that he is hearing.

If the speed measures stable with a strobe then what pitch related anomaly can be heard?

1. Any pitch-related anomaly whose time duration from delay through recovery is shorter than the time that passes between two marks on the strobe disc. This would be a greater risk with low resolution strobes (ie, fewer marks per circumference).

2. Any pitch-related anomaly which slows the platter by precisely one (or any other whole number) strobe mark in 1/60th of a second (1/50 in some other countries). This would be a greater risk with high resolution strobes (ie, more marks per circumference).

A strobe isn't perfect. It's a an unnumbered, circular yardstick with markings giving it one very specific resolution. Changes that are completed below that resolution won't be detected. Changes that cause a whole number shift in mark position won't be detected.

You haven't responded to Mosin's or my suggestion: listen to a good quality belt drive table properly set up with a variety of belts. Hear the differences. Supply some explanation other than speed variation for the differences you'll certainly hear.

"listen to a good quality belt drive table properly set up with a variety of belts. Hear the differences."
Doug, that is exactly my point. If the tt is properly set up and all youve done is change the belt and it strobes the same as the belt you had on before mabey your not hearing speed variation mabey what your hearing has something to do with coupling, damping or? With all the enthusiasm for the idler drive lately why assume the performance is solely (or at all) due to speed regulation since it seems these small deviations have yet to be measured or quantified or much less correlated to a paricular hearing sensitivity.
Thankyou for the fun dialogue Ill sum up by saying "if you dont know what it is you dont know what it isnt" and in that spirit Ill be researching this much farther and will report back on any ground breaking discoveries

This is a shining example of what I was talking about in one of my earlier threads, "The High end and Glubglub". Lifted from a discussions in logical argument and philosophy:

"What he (the skeptic) wants it is logically impossible to supply. But doesn't the logical impossibility of the skeptic's demand defeat his cause? If he raises a logically impossible demand, can we be expected to fulfill it? He says we have no evidence, but whatever we adduce he refuses to count as evidence. At least we know what we would count as evidence, and we show him what it is. But he only shakes his head and says it isn't evidence. But then surely he is using the word "evidence" in a very peculiar way (a meaningless way?), so that nothing whatever would count as a case of it...Might he not just as well say, "There is no glubglub?"" In short, a waste of time.