Turntable speed measurements for speed accuracy?


I'm curious why don't turntable manufacturers publish speed accuracy measurements? Some do, but most don't.
james1969
The quartz units always had a rating since the units design was stable. Belts driven is always if'y, in that the variables, belt age, motor accuracy due to line volt fluctuations etc. were not in the manufacturers control after the units were manufactured.
The reason is that most manufacturers, including those who publish measurements, do not measure at the platter and probably do not know how. What is widely done and extremely misleading, is to report the accuracy of the chip used. This information is provided by the manufacturer of the chip and really has no correlation with the turntable's actual speed accuracy.
It would be nice if review rags would perform speed accuracy tests with every turntable they review. It seems like this is a fundamental specification of performance to actually measure.

If a turntable cannot spin a record at a consistent speed, then what good is it?

Especially the high end manufacturers, if you put a high end turntable on the market, shouldn't you back up your high end design with a standard or reproducible speed accuracy measurement?

I only bring this up, because my last 'high end' turntable costing over $6500 (and this is on the low end for 'high end' turntables) could not play a record and keep a consistent speed. It sure had exotic features on it like vacuum pull down platter, exotic wood finish and '25 years of experience' of manufacturing turntables.

A vintage $300 turntable is able to keep a more consistent speed than a current design $6500 turntable. The turntable drive implementations are different, the vintage table uses a Quartz Direct Drive where as the 'modern high end' table uses a belt drive. The difference was noticeable right from the first song cued up.

I'm sure there is more to a good sounding turntable than just speed accuracy, but I would think this is priority number one? Yes?

Hello,

The problem with speed accuracy in many turntables, as I see it, is that far too many of them depend upon mains current as their sole power source. If a turntable has a precision power supply, then speed control is addressed by default. In my opinion, a turntable's primary tasks are to spin a record accurately, and spin it quietly. Do that, and you are halfway home.

Regards,
Win

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What is widely done and extremely misleading, is to report the accuracy of the chip used. This information is provided by the manufacturer of the chip and really has no correlation with the turntable's actual speed accuracy.
Agreed. There's some correlation but it's hardly conclusive or adequate information.

It's just as inaccurate to report on the speed accuracy of the motor itself. Speed accuracy at the platter is the goal, and it's easily affected by stylus drag. Measuring or quoting specs anywhere but at the platter with the stylus in a modulated groove has little meaning.

If a turntable has a precision power supply, then speed control is addressed by default.
I disagree. A precise source of power is certainly essential, but it isn't sufficient. Power must be converted from electrical to mechanical energy by the motor, wherein many opportunities for inaccuracy reside. Even if the motor does that job perfectly (and no motor does) that mechanical energy must be transmitted to the platter without loss or inaccuracy, another opportunity for errors. Finally, the entire system must be able to overcome the variable load of stylus drag whilst playing real records, an extremely difficult engineering problem.

I agree it's vital, but maintaining constant and accurate platter speed under variable load is a terribly complex problem, and no set of wow and flutter measurements will come anywhere close to identifying how good a particular rig really is in this respect.
Doug,

I agree completely. My answer was simplistic, so that's why I said "halfway there" in my post. There are so many relationships to consider that it is mind boggling. I suppose the real test comes when the stylus hits the record in the presence of experienced, but unbiased listeners.

Regards,
Win
Doug : "Finally, the entire system must be able to overcome the variable load of stylus drag whilst playing real records, an extremely difficult engineering problem. "

There is a name for this, it's called mechanical coupling. I think you are overstating the difficulty of achieving tight coupling, it isn't hard at all as anyone with an idler table can attest.

The difficulty has been getting a motor that runs on speed which is quiet enough to be used when tightly coupled. That difficulty is slowly being addressed through several avenues, some of which haven't reached the market yet.


Mark,

Thanks for the clarity. It is possible to achieve speed stability, as you most certainly know. Still, it is a game of fine tuning that I suppose will always continue to progress. The best we can hope for is a result that doesn't hamper music, and that, like Doug says, is easier said than done.

Regards,
Win

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Just FYI the new Adjust+ software/LP system measures platter speed, wow/flutter, etc. I am about to order one, but there are some options, that are not explained on the the site and I have emailed Chris.
Please report your findings on this software. Sounds interesting...
You must not have heard . . . it has been conclusively proven through many exhaustive hours of turntable-watching . . . oops, I mean turntable-listening tests, that there is absolutely NO correlation between the speed at which the platter turns and the accuracy of the music reproduction.

Oh wait, no that was something else that didn't matter . . . crap. Where's my issue of Stereophile?
I lived with a SOTA Cosmos mk3 for 2 years, then upgraded it to the mk4 status. I could hear the speed UN-stability it was playing with my records. Which is what drew the turntable out into critical listening for me. I could hear the speed change over various songs pretty easily. This turntable retails for over $6500 and it cannot even play a record consistently.

I wonder if it is the belt drive design. Regardless, the SOTA implementation of a belt drive is pretty poor. Compared to a vintage $300 Luxman PD-264 - a direct drive design sourced from Panasonic, this turntable plays at a far more consistent speed than the SOTA.

Have you heard a record played on a direct drive turntable vs a belt drive? I think the reason why you do not see direct drive turntables in the 'high end' world, is because Technics/Panasonic holds the patent for Quartz locked direct drive:

http://www.kabusa.com/ttdrive.htm

There is a link to explain in more detail the evolution of turntable drive design.

Where are the 'high end' direct drive tables? The Grand Prix Audio Monoco table is a new one. Brinkman has a direct drive table now called the Oasis. Hopefully we will see more.