Belt stretch

Rccc,

What makes your limits (or mine) the ultimate arbiter of the possible? There may be one being who could claim that, but you're not Him/Her.

Let's test your hypotheses with a few questions, taken straight from the musical casebooks:

Do you have perfect pitch? If I hit a random key on a piano can you tell me which note it was? If your answer is no, do you therefore argue that no one else has perfect pitch either? Tell it to my mother, she'll laugh in your face. Test her, she'll prove you wrong.

If I play any two consecutive bars from one of 600 long, complex pieces of music that you've heard, can you infallibly tell me:
a) which one of those 600 pieces the two bars came from?
b) what movement they came from?
c) which instruments carry the melody and harmony?
d) what happened in the bars immediately preceding, and what comes next?
You can't do that? Well, neither can I. But Toscanini could. Fritz Reiner could. Vladimir Ashkenazy can.

Can you go to a concert, hear a Mozart symphony for the very first time, then go home and write it out - note for note? You can't do that? Tchaikovsky could and did, when he was 12 years old.

Could you travel to another city to jam with a famous string quartet, and after 10 seconds announce to the first violinist that his instrument was tuned 1/4 tone higher than your piano back home (though you hadn't been home in a week)? Max Reger did that. He was 10 years old.

Can you tune your piano for any chosen key so it's correct out to five harmonics above the fundamental? Debussy could. Did it nearly every day of his life.

I prefer to expand my horizons by being amazed at what is possible, not limit them by deciding what isn't. To each his own of course.

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.

Rccc,

Thanks for taking all the responses so civilly. I hope you don't feel too "mugged".

What I have yet to see is anyone demonstrating a hearing sensitivity of X to speed fluctuation and correlating that speed difference to a belt drive system.

I guess that's the core of your position, an honest skepticism about the audibility of belt stretch or slip (assuming a properly set up rig of good quality). Fair enough.

Forget the theoretical arguments. Just listen for yourself. Come over and visit. We'll play some tunes using our most optimized belt. I'll then switch to some other belts we've tried, which are stretchier and/or more slippery.

If you hear the difference (which I guarantee) would the demonstration be convincing? Or am I missing your point?

Jean,

You were doing okay until you said, "a rubber wheel grips without deformation".

Pardon me, but that's nonsense. Rubber is an elastic material. Elastic materials ALWAYS deform under load, then rebound back toward their original shape when the load is reduced - that's what "elastic" means.

Another aspect of this is that energies stored in an elastic material by compressive deformation are released with a time delay when the material is allowed to rebound. Depending on the TT design, this energy normally feeds back into the platter at a fairly low frequency. The cartridge picks this up as "mud" - nothing you can specifically hear, but a lack of clarity and some opaqueness to low level detail. Very TT specific, but a real engineering problem nonetheless.

If you believe a rubber idler wheel (or a rubber anything) is not deforming, you're fooling yourself. The amplitude and frequency of deformations may be adjustable by choosing rubber of different durometers, but they can never be eliminated.

That said, we're in agreement that Rccc should listen for himself. He'll hear what he hears and can make informed TT choices based on his own sonic sensitivities and musical priorities.