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
I have just fitted a thread drive to replace the rubber belt on the Raven AC-2 (thank you Daniel for the Bavarian thread)........and apart from the increased accuracy in speed constancy over the original rubber.......the actual improvement in sound is astonishing?
The bass appears to have added a half octave in depth, the clarity and dynamics have improved and the sense of excitement and realism on every track is palpable.
Is there more to this than speed consistency?

Incidentally......I had to reset the speed on the Raven motor controller because of the differences in force transfer between the rubber and the thread and I used the KAB Strobe initially to find the 'ball-park' setting.
I then set the 'correct' speed using the Timeline and the adjustments to the controller were quite severe. I'm not talking fine adjustment here.........it required about 7 or 8 presses of the 'faster' button to reach 'correct' speed over that settled by the KAB.This is rather a serious indictment of the KAB which simply cannot be correct?
I don't know if it's just my strobe or whether this is endemic to the functioning of the KAB?
I know that the Timeline is exact as it agrees 100% with the speed indication on my Victor TT-101 DD turntable which is quartz locked.
So the question to those relying on the KAB or other versions of a strobe to set the speed of their turntables........you may wrongly believe your speed is correct.
And to those who state that it doesn't matter......how do you know when you haven't heard?
I'm sure because TTWeights places many ads here on Agon they had a BIG say in why the thread was closed. My own search for a table that has spot on accuracy still continues......
I have just replaced the rubber belt on my Raven AC-2 with the Bavarian thread sent to me by Dertonarm ( thanks Daniel).
The speed consistency is slightly improved with this thread drive but the sound of the turntable has been somewhat transformed.
There appears to be a half octave of added bass together with an increased level of excitement and realism to each and every track and record.
Is there more to the drive method than pure speed accuracy?
When I changed to the thread drive, I needed to adjust the Raven motor controller to correct for the differing characteristics and I used the KAB Strobe to quickly get me to the 'ballpark'.
I then installed the Timeline and was shocked to find how inaccurately the platter was now running? I needed to press the 'UP' button about 7 times to reach the correct speed on both 33.33rpm and 45rpm.
When the speeds were corrected with the Timeline......the KAB Strobe indicated incorrect speeds!?
I know the Timeline is correct as it agrees exactly with the speeds on my Victor TT-101 which are quartz-locked.
Perhaps it is only my KAB Strobe which is faulty?.......but I urge caution for all those relying on strobes to set their speeds?
And for those who claim that speed accuracy does not matter.........how do you know if you haven't heard it? :^)
Halcro, interesting and thanks for sharing. What's very interesting is if you already had it set-up for accurate speed with the belt which I assume you did and by just installing the thread the variance.

Is the thread now longer then the belt size was? Not the same tention possibly?

Another tweak to try would be with your table is to use only two motors, have one motor on each side with separate threads but only one operational motor.

Are you not concerned with the thread maring the platter POD material? D mentioned someone else whom did this and it did such so this person has since moved onto using a 1/4 mylar belt and actually has the two motors set-up as mentioned above. Table being isolated separate from the motors.

I also have the thread on hand and my table being the TW BK with an almost all copper platter being mostly different than yours I'm concerned and have yet to do it, last thing I want to do is damage the looks of the platter.

On tables like the MS appear to be no issues due to the different plater material, gun metal or stainless.
Dear Henry, What about listening? When you set the table up using the KAB vs using the Timeline, were there any audible differences? If the KAB was that far off, on the slow side, you ought to have heard it in the form of pitch distortion and/or rhythm distortion. One would have to think that one of your two devices might indeed be defective. Either that or neither is quite accurate.

I had an interesting experience just a few days ago. When I originally set up my Lenco, I had it running at 33 rpm per the KAB strobe, with AC direct from one of my dedicated house lines. (You can adjust speed on a Lenco by moving the idler wheel up or down a tapered shaft driven by the motor.) Then I inserted my Walker Audio motor controller and had the Lenco set at exactly 33 with the Walker. Then some months later, I removed the Walker and was running direct from the wall socket again, but I had not re-checked the speed when I went back to house AC. The other day, I had an audiophile friend here listening with me to the Lenco, and he remarked that it sounded "slow"; he perceived a pitch problem. So we took out the KAB strobe again, and indeed, with the stylus in the groove, the Lenco was slow. I was embarrassed that I had not picked up on this problem. However, after he left, I realized that I had been bothered by the musical timing with the Lenco. Tempo seemed consistently "slow", but I heard no real problem with pitch. I had even wondered why Ella Fitzgerald had chosen a slow tempo for a Harold Arlen tune that I considered to be a good swing. The point is that what he perceived as a pitch problem was perceived by me as a timing problem. Obviously, tt speed affects both. I subsequently re-inserted the Walker and now all is well. The brain is a funny organ. He cannot sing to save his life, and I am a long time amateur jazz singer. You would think that I would have at least as good a sense of pitch as he does.