Turntable speed accuracy


There is another thread (about the NVS table) which has a subordinate discussion about turntable speed accuracy and different methods of checking. Some suggest using the Timeline laser, others use a strobe disk.

I assume everyone agrees that speed accuracy is of utmost importance. What is the best way to verify results? What is the most speed-accurate drive method? And is speed accuracy really the most important consideration for proper turntable design or are there some compromises with certain drive types that make others still viable?
peterayer
Dear Halcro,

your new experience with a thread driven Raven sounds good.
Next, you could try this:
- disassemble the three feet from both of your motor housings
- set up the housings flat on some kind of damping mat (a piece of anti-drone mat for washing machines would help)
- rearrange the strings

Now the motor housings are no longer able to wobble slightly on their feet (that's particularly the case when strong tension of the belt/tape/thread is applied). In my experience this has also positive effects on speed consistency and sound improvement.
Halcro great to see you trying the thread drive. The pulley shape should be concave for thread drive so it self centres and does not ride up and down.
Dev I have been using my thread drive final audio Parthenon for over 20 yrs with silk thread , surgical silk, quite high tension and there is only a very faint mark on the platter, no wear.
Okay, I'm sure that I'm missing something hear as it relates to the Timeline. . .

Sutherland states that if your turntable is spinning at 33 1/3 RPM it will take 1.8 seconds to complete a revolution. His Timeline flashes at this 1.8 second interval, and if the revolutions are precise, the laser image will hit the same spot on the wall with every revolution. Makes complete sense.

However. . .33 1/3 RPM means that in one second (33 1/3 divided by 60 seconds/minute) your table will complete .5555 revolutions, or one revolution every 1.111 seconds, not 1.8 seconds.

What am I missing?
It's actually 1.80018... I think it's a repeating number. Let's hope Mr. Sutherland set his timing thus. Otherwise, the instrument is off by .00018 sec per revolution. Apparently this much error would drive some of us crazy or to a new turntable.