A Few Turntable Measurements using the RPM Android App

@mijostyn The belt is brand new. Just put it on about a month ago. The old belt had stretched. The measurements I reported using the RPM app were done with the new belt.

 I was shocked by the poorer performance of the WOW. Acoustic Signature does not publish specs for speed stability, wow, flutter and rumble.

Seems that AS relies on the marketing of their special spindle material, the huge platter and the brass inserts to impress buyers. Must be good performance with all those buzz words, right. A simple measurement shows the difficulty of relying on bling rather than real measured performance. I was fooled. I bought it. One of my biggest audio gear mistakes. Won't happen again.

I believe in these RPM apps!  Perhaps that is because my 42 year old direct drive Denon DP-30L measured so well. Spot on RPM and decent wow. Thanks for the tip!

@brev Yah, it is fun making these measurements. I wish that the developer would publish his/her methodology. For example, what algorithm is used for the WOW calculation? Is it one of the standards?

I don't think we'll find out any time soon. Apps are usually closely guarded secrets.

But he/she could indicate which standard he/she is following, if any. Without this knowledge, it is impossible to compare RPM results to manufacturers' published performance.But relative performance between tables is valid.

Dear @kevemaher  : As you I bougth my units at blind on specs and were ( two units ) coming from an audiophile that I respect, so second hand at very good price: 2 top of the line ( in those times. ) TTs with 3 outboard motors and one motyor controler that I had to modify to choose between one TT or the other and till today I have not a single issue with those AS and the " belts " I use are simple silk thread amnd yes I have to push-start. In reality a critical issue with my model TTs was that came with no kind of damping footers so what I did it is to put 3 AT-616 pneumatic Audio Technica footers and a top these footers goes a centered an inverted aluminum tip-toes that for me makes very good job.

Here you can read some real time measurements in one of AS today model:

https://www.acoustic-signature.com/files/downloads/tests/2021-08-stereoplay-double-x-neo-ta-500-neo-mcx1-en.pdf

R.

@rauliruegas Hi, Thanks for the link. Surprisingly, the wow and flutter reported for the Double X by the author of the article you referenced is the same as the wow value I reported above for the AS WOW XXL using the RPM app. This result is encouraging, but not enough for me to trust completely, because the method of analyzing the data may be different.

There is no denying that the Double X measured wow value is 5x higher than the 0.02% I measured for the DP-57L table using the RPM app. Even more damning, the Double X it is worse than the wow reported for the Micro Seiki DD-40, an "entry level"  turntable.

The rumble spectrum is also quite informative. Although I can't make a 1:1 comparison with my (unpublished) results because gain and reference voltages may differ, I can say that the rise in noise from the 500 Hz baseline to the peak at 10Hz is about 60 dB for the Double X table in the article. I'm using the blue curve. This may be an incorrect trace, but there is no legend to indicate what the conditions were for each curve. My results indicate only a 30 dB rise for the DD-40. This is a 30 dB (30X) difference!!! Perhaps the region around the Double X was particularly high in vibration on the day of measurement. Or the line filtering in the Double X power supply is poor design or faulty.

One can also see the on the same chart a 50ish Hz peak.frequency. It rises 60dB above the baseline. The source is not identified, but is probably the AC line frequency. My measurements used a rumble track on the Hi-Fi News test record. The AC peak for the DD-40 is not visible, buried in the noise, which is already lower than the Double X.

It is very obvious now why Acoustic Signature does not publish these specifications. It could be very difficult to explain why a 70s "entry level" table beats their Double X for wow, flutter and rumble.

With all this now under our belt, can one say which table sounds better?

No.

But if one had to pick a table based on these results, the choice is clear.

I am also boggled to read that the reviewer summarized that the Double X performance as "high end".

How low do wow, flutter, and rumble have to be before they become inaudible in a "typical" listening situation? If the value is higher than that of every measurement result shown here, then the better performance of the DD-40 and DP-57L is not really needed. The Double X performance will be indistinguishable from those tables. But I think the answer is that since the manufacturer cannot control the conditions that a buyer will use its product, the manufacturer must strive to equal or beat the performance of the other "high end" tables.

If none of those publish these specs either, then my entire discussion is meaningless, since there's no way to determine from measurements which table is "better". Listening is always a very good method, but is usually highly compromised in any showroom environment. Perhaps listing is the only spec to test for. But how many people purchase a table without extensive listening to it prior to that purchase? I'd wager most do.