Direct drive vs belt vs rim vs idler arm

Yes I agree, thats pretty much what I proposed for testing to quantify the variation between that minimum and maximum drag levels and the impact of a piece of music in total...I think you misread my syntax ( no pun intended ). ("how consistant" , ie I meant range of variation. )

I am wondering that every Turntable discussion is based on speed only. Like Dev wrote, it is the beginning and it is important. But is that all?
A little more knowledge should be available I think, we have the year 2013 now and serious High End has 5 digits or more and a lot of owners want to spend that money

- Quality and Influence from the Bearing
- Quality and Influence from the Chassis
- Quality and Influence from the Belt
- Quality and Influence from the Platter
- Influence from Suspension and how it was solved
- Why are some platters so heavy
- Direct Drive works with continuous correction, what is the sonic result
- Platter weight from DD and their sonic attributes
- Weight in general and why
- Is a polished frame good for sonics
- Idler Drive has direct contact to Platter and Spindle
- Advantages / Disadvantages
- Speed correction or not
- What material is used and is it stable over the years
- suspension for Idlers, necessary or not
- sonic results from contact motor to platter
- isolation from internal vibrations in general
- is reliability important or not
- do Fangroups replace knowledge
- are facts welcome or do they disturb dreaming
- why are no turntable manufacturers found in such discussions
- is analog the last resort for "I-do-what-I-want-and-who-cares-Design"
- what is a stable Design
- why can a unit change Performance when your wife opens the window
- what is sonic feedback

and so on and on

Hi Dover, one thing to quickly recalculate is that the record spins 0.5556 revolutions per second. (Inverse of 1.8) So the speed error would be 0.008% if it takes 7200 seconds to lose/gain one rotation.
What I believe is that we will hear a difference in PRAT if speed is off before we hear sour notes (tonal pitch); at least most of us. If speed is off by 0.1%, then concert A would be off by 0.44Hz. I do not think that I could tell the difference even if I had a tuning fork to my ear. But I now know that I can sense the pace of the music by small changes in speed. An orchestra, for example, tunes to the oboe. If the oboe is off a Hertz or two, it doesn't matter because the whole orchestra will be matched to it; but the tempo of the music doesn't change- can't do that with a recording.

Your tt platter is a flywheel. Like any good flywheel design, the bulk of the mass is on the outer edge (Think 2001 A Space Odyssey). The moment of inertial equations illustrate the effectiveness of having the bulk of the mass at the outer edge. A uniform mass flywheel is I=1/2mr^2, but when the mass is concentrated at the outer edge it is I=mr^2. The moment of inertia is doubled. Therefore, a "hollow" flywheel half the mass of a solid flywheel has the same moment of inertia. And the moment of inertia is directly related to the amount of torque it takes to accelerate the platter- double "I" and torque must double to get the same amount of acceleration. Conversely, double "I" and the impact of stylus drag change on platter speed drops by half.

Here is another thought to feed on our neurosis. (I hate to suffer alone :) Like I have said before, the tolerance on the center hole of records is such that the record Wow&Flutter is going to be around 0.5%. My favorite iPhone app will show you that too. It will show you the raw W&F as well as the filtered W&F of your tt. Last Winter, I filed out the center hole of my test record a bit so I could center it on the tt platter. It worked and I was able to reduce/change the record W&F. It is not easy to do. The outside diameter of records is not that round either. I had to try to center it relative to the grooves. But now, think about this. Your turntable has W&F in the 0.03% range and a typical record, say 0.5%. The two values are additive, so depending on the position of the record relative to the platter the total W&F could be 0.53% or 0.47% or somewhere in-between. (Min and max values worse case). So it is very likely that you could play a particular record one day and it seems to sound really great- pace is on and the music flows and the next time it sound kind of dead- all based on the randomness of the record position to the platter. Other than my test record, I have never experimented with this concept. I try not to think about it.