How important is low W & F performance anyway?

Now, a question to you: can you be aware ( everything the same ) between 0.03% and 0.0018%? and how identify you that difference by ears?

My hearing is not very good so I'm not a good example for this.  The mfr is an audiophile and musician and he could hear differences that I could not.  When we were tuning the control loop, I gave them ability to modify it in real time while they were listening to music and the person making the changes did not inform the listeners when he made a change or what change he made.  The parameter he was changing was the gain in final output stage;  it did not change the W&F measurement significantly (the overall reading stay centered around 0.005%) but it did change the spectrum of the signal derived from the optical encoder.  The sidebands stayed below -60dBc but the primary bump in the response shifted location (closer or farther away from 3125 Hz).  The listeners reported a subtle change in the voicing of the table from "more analytical" (higher gain) to "warmer" (less gain).  We ended up adding a user adjustment for this to customize the voicing of the table to enhance or compliment the user's system or to match their preference and set the factory default level to midway between the two.

@phoenixengr 

Multi track tape machines typically have a wow and flutter spec of .1 % or higher.

The revered Scully lathe was .2. 

Were the turntables in question using the same test specs as the manufacturers, IEC, CCIR, DIN? 

@billstevenson 

Congrats on a good find, and that it measured so well. I tell others, they are solid, a darn good choice for someone getting started in Vinyl.

Were the turntables in question using the same test specs as the manufacturers, IEC, CCIR, DIN? 

Are you asking about my test method or the mfr’s test method?  The mfr’s published specs do not indicate which method and/or weighting they used (I suspect they don’t actually measure anything, they just pull numbers out of the air given the discrepancy between specs and actual measurements). Different methods will produce slightly different results but they shouldn't exceed a ratio of ~2x.

The polar plot software I have uses 2-Sigma method, unweighted.  The BW is adjustable up to 200 Hz.  Multi-Instrument software uses RMS and 2-Sigma but it does not necessarily conform to the IEC/DIN/CCIR specs for the center frequency.  The Leader LFM-39 is selectable. 

All of my measurements were taken from the output of the encoders used for closed loop feedback so the center frequency differs from any of the standard tests, but the signal is free from record defects, off center pressings, or contributions from the tone arm or lathe.  It should reflect the most accurate movement of the actual platter.  Too many of the commercial offerings for W&F measurements attempt to filter out contributions from the LP/tonearm and in doing so, remove valuable information about the drive.  It’s important to look at not only the amplitude of these deviations but also the spectrum.  Multi-Instrument software and the HP 35655A dynamic signal analyzer provide this.