Low Cost Turntable - Incredible Performance

@richardbrand Thanks for taking the time!

I still do not understand the 4 Hz. Table rotation is 30 RPMinute = 30rp/60s = 0.5 rps = 0.5 Hz. Off center record spinning should be correct 2x revolution (thanks for this!) so record wobble frequency is at 1 Hz, not 2 Hz.

If the test tone 3150 Hz frequency is sampled with a measuring frequency of 4 Hz, so 4 times per second, one gets 8 data points per revolution: 2 at minimum speed/tone frequency, 2 at maximum speed/tone frequency, 4 at in between speeds/frequencies. That then measures the precision of the average speed, how close the platter rotates to the normative 33.33. Given that there is no perfect record, one has to take the wobble of the record out to assess the actual TT performance.
It also suggests that the % metric is derived from a Fourrier transformation of the received tone signal. Then I can see how you can look at maximum deviation above and below 4 Hz in the transform. It appears that it is critical to make the distinction of tone frequency and measuring frequency. 

The deviation above 4 Hz in the transform is microspeed variation of the TT.

Re tone variability of 3148–3152 Hz, so delta of 4 Hz, that is <1 cent (800 cent = 1 octave = doubling of frequency). In sequence, indistinguishable, even to trained musicians. On a good day, I can do 3–4 cents when tuning. <1c is in comma territory, and if that would be objectionable, then any equal tempered piano would sound bad. [It does, but that is my personal dislike of the instrument and preference for HIPP baroque music].

Well familiar with interference. Easy to generate on a violin. Interesting concept re flutter affecting sustained notes. However, considering a perfect TT, direct and reflected sounds are also out of phase due to different travel distances. The phase difference has nothing to do with flutter, only with direct vs. reflection, plus there are various reflections (side, floor, ceiling, back wall ...). Not sure I buy that rationale, but a fun thought experiment.

Additionally, in classical music, sustained notes are smeared with vibrato (as opposed to note shaping with messa di voce in HIPP baroque playing). So any microspeed and reflection variation is lost due to the dreadful vibrato sauce. 

I happen to still believe you’re better off investing in some of the used direct drive tables of the 80s and 90s

^this. 

There are not many recognized experts  on the care and feeding of vintage Japanese DD turntables.

@mikevanloo @lewm 

Here is one. If you live in Perth, Australia, he’s just a short drive away.

https://liquidaudio.com.au/

My first turntable was a Pioneer belt drive semi-automatic bought in 1975 for about $150.  Loved it to it's demise after 35 years in service.  

RB, You wrote, "Direct drive tables tend to have worse flutter than belt drive, because direct drive uses impulses to rotate the platter while elastic belts tend to absorb vibration from higher speed motors."

First, is the premise correct? Do DD TTs in fact have higher flutter than belt drive?  I don’t know one way or the other. But to your following point about DD TTs using "impulses" to rotate the platter.  This sounds like the old "cogging" allegation that BD lovers foist on to DD TTs. The treatment of cogging is either to use a lot of poles, so the impulses are very closely spaced, and there are other tricks of the trade that address the timing, all of which are very effective in rendering cogging inaudible. Modern or even late 20th century DD TTs don’t have audible cogging. Plus many of the best DD TTs use coreless motors that are inherently free of cogging.  As to the bit about the belt absorbing motor irregularities in a BD TT, that depends entirely on the compliance of the belt, and that speaks to one of the most common points of discussion with BD. Should you have a noncompliant belt so the motor can control the platter as stiffly as possible (but this allows noise transfer) or a compliant belt that isolates motor and platter, relatively speaking, but allows stylus drag and any other sources of friction to slow the platter before the motor can compensate, even assuming the motor is seeing some sort of feedback vis platter speed? With a compliant belt the platter speed can vary up and down, as the motor tries to catch up with what the platter is doing. Like "cogging" with DD, the issue with belt compliance and motor torque in BD TTs is more for argument's sake than it is a major determinant of SQ, assuming well designed and built examples of each type. But there is no free lunch.

thecarpathian: Glad you posted that chart. It means I can keep my crappy old Technics SL-1200 ML2. It is listed at .01 or .025% WOW depending on the method used.