Has anyone had trouble with speed on their tt

We have yet to define speed stability.

Glad to see someone acknowledging the complexity. The definition is actually simple. What's infinitely complex is the number of different time periods across which speed stability must be maintained - simultaneously - to assure musically accurate reproduction. This is routinely glossed over in discussions of speed stability.

No strobe (Timeline or otherwise) operates in short enough increments of time to detect micro-/pico-/nano-second variations. Knowing that a TT is speed stable across a time span of minutes tells us nothing about how stable or unstable it may be across a few thousandths or millionths of a second. Such short-period variations are just as audible and musically important, arguably more so.

The Timeline whoopla only considers speed stability across relatively lengthy time periods. While not insignificant, this ignores short-period speed stability issues that are more significant - at least to my ears. Its a bit of a tempest in a teacup.

I count three speed related issues with turntables.
1) Absolute speed- this is what the timeline device can measure with utmost
accuracy. This is the least important of the speed issues with regards to how the
music sounds. If the platter speed is off 1% or less, who cares? You will not
know it unless you have a tuning fork near one ear while playing a record with
the same frequency tone for comparison.
2) Slow variation in speed. I'll define this as Wow&Flutter; which could also
include speed variation beyond the 1.8 second period if a motor controller has
an issue or if line voltage is an issue. The record itself is usually the biggest
contributor, (if you have even a decent level of turntable), to Wow&Flutter due to
center hole tolerances. If bad enough, piano notes sound sour. This is a more
critical issue than absolute speed.
3) Fast variation in speed. This is the big one. Take a look at my system page
for more detail about this. This was an eye opener for me. A lot of potential
contributors to this issue. The biggest problem here is that you may not hear it
or notice it directly; but once this type of issue is resolved you will be amazed at
the difference in sound. My contributor to fast speed variation was my
turntable's suspension system. It was causing high frequency oscillations in the
platter. Other contributors to fast variation in speed could be due to cycling of
closed loop controllers about the speed set point, speed controllers that
constantly adjust speed, motors with too little torque to overcome stylus drag
during loud passages, or motors with too much torque and also belt problems.

I believe that listening is the final test in evaluating a system; but I also believe in
using measurement tools to reduce time and trials in getting to that final
listening test. I put a lot of stock into Dr. Feickert's iPhone app. Use it as a
relative tool. I think the frequency measurements are dead on because the app
uses the iPhone's internal clock.

Dougdeacon said...

"No strobe (Timeline or otherwise) operates in short enough increments of time to detect micro-/pico-/nano-second variations. Knowing that a TT is speed stable across a time span of minutes tells us nothing about how stable or unstable it may be across a few thousandths or millionths of a second. Such short-period variations are just as audible and musically important, arguably more so."

Brilliant. This is so true.

Tonywinsc also touched on the same point.

IMO it is the reduction of these tiny speed changes that is one key to a TTs performance. Do we have a way to objectively measure this? Maybe, with some of the new optical speed sensors capable of measuring greater than 1x10^6 counts per rev, but I sure know that we can hear it.

Read Doug Deacon's last post again. He gets it.

Zavato said, "stick with a design that has an AC synchronous motor and a platter heavy enough to have some flywheel effect."

I could not disagree more. Flywheel effect caused by the platter is the reason many turntables lack micro dynamics, or sound lackluster in more general ways. It is a simple case of letting the platter control the speed, rather than the device assigned the job, the motor. That doesn't work, if you want a turntable that is truly precise.