Turntable Speed: What matters?

The red and blue lines are passes. Differences from it being a perfect circle are variances in speed. If you have a test tone and the tone goes up or down intermittently then the speed is going up or down. How centered it is, is mostly how centered the record actually is.

It shows pitch stability, which is also speed stability. It isn’t a tachometer. The other measurement is about amplitude where you can see resonances.

Folsom said:

It's not that I want to crash your party but if you want to do real measurements this thread is all about it. What they're doing tells you more than any tach or other simplistic measurement would ever tell you.

Click to expand...

I checked the link and read at least 6 or 7 pages. With all due respect I hardly called them "real measurements". Those are mainly FFT analysis of just 1 second or less of 3.15khz test tone track. There are lots of post about resonance frequency, FM distortion and vinyl eccentricity. It's good to know some people show interest to those stuff but a proper test method for wow&flutter requires more than 1 second of evaluation, DIN or better AES standard duration in that case. Because wow&flutter is a function of change in speed over time and that's why evaluation time is paramount for the end result.Those pages you shared contain primitive good information but nothing fancy about FFT analysis with a software oscilloscope. There are so many things to talk about on this subject but in that regard a plain RPM app or better turntable speed app on ios can give you better results on wow&flutter. They're not very accurate but better than basic FFT analysis or beam forming.

I have no idea what you’re talking about. Firstly wow and flutter are the same thing just measured on either side of 4hz. Secondly they’re akin to using a tachometer, they are a percentage.

Doing it like in that thread will show you if you have a bearing problem if speed is stable in half a rotation for example but mixed in the other half. Wow and flutter would just give you a group percentage and inform you nothing about the bearing mostly working. There is less to learn without the visual.

Would I describe it as perfect? No. But there are give and takes. You could take a basic same measurement with equipment described in the thread, and average them over playing a huge variety of different albums. It’d be expensive and maybe not really any more informative. It would be the same information that a wow & flutter measuring device uses except you wouldn’t have to live with a mostly useless percentage figure; like with what manufacturers give.

Also, I don’t know why you have a problem with FFT. There are more steps in an wow & flutter percentage for representation. I mean it’s like arguing that you don’t like charts for stocks, and prefer to just read the order book of purely price and amounts…

Folsom said:

Also, I don’t know why you have a problem with FFT. There are more steps in an wow & flutter percentage for representation. I mean it’s like arguing that you don’t like charts for stocks, and prefer to just read the order book of purely price and amounts…

Click to expand...

I like FFT and use FFT spectrogram for audio restoration all the time. In my prior life I was looking FFT waterfall constantly cause our lives used to depend on those graphs.

Folsom said:

I have no idea what you’re talking about.

Click to expand...

Let me explain what I meant on my prior posts. FFT is a useful tool but a snapshot is not enough for wow&flutter measurements. There are two different things, one is wow&flutter the other is speed accuracy. You can check speed accuracy with a snapshot FFT (like the ones in the link you shared) but you need a predetermined time of measurement for wow&flutter evaluation (AES, DIN etc). A single revolution or one second of measurement is not enough for wow&flutter.

A turntable that runs at 34rpm with a %0.05 wow&flutter sounds better than another identical turntable which runs at 33.3rpm with %0.1 wow&flutter. Speed accuracy can easily be fixed by adjusting motor speed but it’s hard to fix bad wow&flutter. Additionally it’s very hard to detect a turntable running a little bit slow or fast but it is easy to detect good or bad wow&flutter. Lower wow&flutter enables better pace, rhythm and tone which is very noticeable with piano and violin sound. That’s why it’s more important.

I don’t say that FFT graphs in the forum you shared are unimportant or meaningless. On the contrary checking speed accuracy and bearing chatter is very important. I wanted to point out the significance of wow&flutter.