Turntable speed accuracy

While there is tremendous value in technical explanations for some of the perceived problems with vinyl playback, I think it is important to remember that those possible explanations are incomplete, and don't fully address the fact that what we are ultimately concerning ourselves with is an impossibly complex and fragile thing: the FEELING in music. Small speed stability problems that affect the perceived feeling of the music, wether caused by run-out errors or rotational speed error, are probably beyond the capability of any known measuring system.

I have (like all of us posting on this thread) struggled to make my
expensive belt-drive turntable as speed-stable as possible. Thread drive and a motor controller have improved the situation to a barely acceptable point. I say barely acceptable because I can still hear problems compared to the rock solid stability, and fabulous swagger that live music can have. In addition, the very same LP that has no perceived run-out issues when I use thread drive, will sound speed unstable when played using the rubber belt. This, in spite of my strobe showing that the speed should be rock solid. NOT!

Halcro, another way to do it is with a stopwatch if you are fast enough. The motor should be able to accelerate the platter from 0 to 33.33 rpm in less than 3.6 seconds. So you could start the laser then start the motor and stopwatch and time it until the laser spot stops moving.

Tonywinsc,
Your explanation makes a lot of sense to me....especially with my experiences with DD turntables compared to belt drive.
I'll try your experiment with the one revolution......although I'm not quite sure what it proves?

It will show that the designer used a motor with sufficient torque to maintain a stable speed.

Keep in mind that the effect of the vinyl record runout is worse at the inner groove. As the needle is further out from the spindle the radius of the runout is proportionally smaller so Wow will be less at the outer groove of the record. So effectively another problematic issue when playing the inner grooves of records. Does anyone notice a rhythm/timing difference in the music from the outer to inner tracks?