Direct drive vs belt vs rim vs idler arm

1) The Final has been shown, through your own testing, to slow down due to stylus drag.....end of story
2) You are quite right, the Final has much higher intrinsic resistance to stylus drag than the other TT's mentioned...if you assume that the others have their servos disengaged
3) Cogging, if present, at 11hz for the DD example you gave would be easily mitigated by a correctly operating servo. The corresponding frequency for the thread drive you mentioned would be around 120hz, with no servo present to corect. I leave it up to the listener to decide which frequency, would be the most benign. If you are talking about what I call "jitter" a much higher frequency artefact common on DD's, you will have to wait for my upcoming web site to see how it is addressed.
4) You need to revisit your laws on motion to see what happens to ANY drive system that does not reduce torque to stasis levels at design speed.
5) Regarding the 1000 tonearms, phase switching, full cycle detection FG, double servos,SPZ, high kinetic energy of rotation, sine cosine, et el. you shouldnt believe everything you read in sales brochures. They are, afterall, trying to seperate you from your money.
5) Hopefully, for the last time. There are many paths to enlightement. You like the Final, thats great. Enjoy the music it plays. This hobby of ours in not a competition.

Richard
1) The 0.0008% speed impact from stylus drag I measured on the Final is insignificant in the context of the other issues raised such as eccentric records etc - the ones you believe are spurious. The measured speed change is less than the wow and flutter quoted for both the SP10 and L07D with their speed correction engaged.
2) I recall you said it was a myth that the servos are operating frequently, and I assume they only occur after the drop off in speed, which will initially be higher as you acknowledge.
3) Cant comment on cogging as I dont have enough knowledge other than I can hear it on most DD's. You have acknowledged that whilst they may occur at different frequencies the magnitude is lower with the higher speed motor.
4) Pass
5) I dont believe much of what I read. Having studied engineering at the University of Auckland it is easy to identify the contradictions within the brochures. For example, as you have alluded to, there is no way the Technics would support the load of 1000 tonearms without the speed correction being employed.
6) No doubt there are many paths to enlightenment, but you haven't convinced me that speed correction is required on all turntables, which was your original assertion, based on your observations of the performance of a Goldmund Studio which I believe is a very poorly designed turntable.

Yes, thank you, I have enjoyed the Final for over 20 years.
It has not required a new plinth, redesigned power supply, additional mats & clamps , or any further expenditure to address inherent design issues.
It continues to be state of the art some 40 years after production commenced.

Gentlepeople
The problem with posts like this, where a difference in opinion is being aired, is that there is a tendnacy for us to talk past eachother and place significance on things that are written outside of what the author meant. This is perfectly natural.
That said I will try to clarify what I meant with my six points.
1) and 2) The Final has higher intrinsic resistance to stylus drag due to its platter which has a higher moment of inertia than the other two TTs, ONLY if you turn off their servos.
With the servo in play The SP10MK3 will show NO measurable speed change with retardation torque levels up to 10KG/cm. In their literature they use the analogy of 1000 cartridges tracking simultaenously. So we can infer from this that 1001 cartridges tracking will cause a speed change. I note that the Final slows down with 1 cartridge tracking. Lets make this clear, speed change due to stylus drag on the SP10MK3, even with 1000 cartridges in play, is so small that it is undetectable. You can take it then that I did do not acknowledge that the initial drop of in speed would be higher with the DDs. While a speed change must be there, with the SP10, it is not measurable. This is where correct matching of motor torque capability, servo characteristics and platter moment of inertia are critical.
I do not have data on the LO7D, but I expect that it would also perform well on this front.
For me the problem with speed changes due to stylus drag is that they are a function of the music being played, unlike wow and flutter which are independant of the music. Much like tape hiss, we can listen past w&f to engage with the music. This is not possible with stylus drag speed problems, as it is inside the music itself. That said it is obvious that lower w&f would be better.
Record concentricity problems are a pain especialy when one has just put down good money for a new record. But this is not a platter speed accuracy issue, so in that sense it is spurious to any discussion on absolute platter speed accuracy, even if its effect dwarfs any platter speed errors.
3)Cogging. I don't want to put words in your mouth, but I don't think that what you are hearing is actually motor cogging as in the physical effect of the motors construction. The very low frequency at which actual cogging occurs is, I suspect, not what bothers you. I do agree that there is a problem with many DD's, but it is not physical motor cogging and it can be fixed. (Maybe the Goldmund should be outside this comment.)
4) 5) Stasis torque levels. The platter will speed up if the torque output from the motor exceeds that requied to overcome bearing friction, stylus drag and windage. Not enough torque and the platter will slow down. Drive systems revert to stasis (low maintenance ) torque levels once design speed is reached. This is taught in engineering classes. Putting this another way. Motor torque output is a function of the load.
6) You are totally correct when stating that the DDs need a lot of work to bring them up to their potetnial. This, however, does not detract from the fundamental performance of the drive method.
Lewm said "If you prefer your thread drive to any and all direct-drives you have ever heard, that is all well and good. I am sure it is superb. But I don't think you can prove from first principles that it is inherently superior to all direct drive."
Totally correct. The opposite is also true, so let's call it a day and both enjoy this thrilling hobby of ours.

Dear Dover, I have no issue with anything you say, where it's a matter of opinion. And I believe you are totally honest when you relate to us that there is something about the "sound" of the direct-drive turntables with which you are familiar that you don't like, or you don't like as much as you like your Final. Quite apart from what Richard says, my problem with your statements is that you are relating whatever it is you don't like about DD to a known issue with all motors (cogging) or to servo effect. As audiophiles we all have the tendency to impute cause-effect relationships like this, when in fact few of us ever do the necessary experiments to prove the relationship. You may dislike DD; that's fine. But you don't know that what you don't like is directly related to cogging or servo. (In fact, which is it, cogging or servo action? You change the tune on that with regularity.)

In my system, I have a highly tweaked Lenco, a Technics SP10 Mk3, and an L07D, all set up side by side by side. They are each very different from one another in the method by which speed is "controlled". (As I have mentioned previously, the only meaningful attack on cogging is the coreless motor; L07D has that feature. But the Mk3 is just as good if not a touch superior to the L07D, with its monster "cogging" motor.) They are all superb turntables; they are more remarkable for their similarity in "sound" than they are for their differences in sound.

I hope that the DD turntables upon which you have made your judgement were properly serviced and adjusted. Leaky capacitors and the consequences of same (blown solid state devices in the speed control electronics) can take a toll on the performance of DD turntables that is not readily apparent, i.e., the table may still "work" but may not be working to its max.

Lewm - in my posts I have tried to relate what I hear with the design etc. Some folk misread stuff. I am not anti direct drive or any drive. What I have heard in very good systems is that there are very few DD's that dont sound awful, by which I mean grainy, grey, music dissembled, fragmented, a lack of dynamics and transparency. The only ones I've heard that dont sound awful are the SP10mk3 and L07D. The Goldmund I heard had a rebuilt and upgraded power supply, many other upgrades and was in very good state of tune. The standard L07D demolished it - demolished it. Demolished it in terms of speed and timing. The Kenwood sounded more lucid, crisper and cleaner. I use this example to illustrate that in my view if you are running direct drive it needs to be at the level of the SP10mk3/L07D at least or you may be better off with an idler or belt drive. Ironically the Goldmund would probably pass the Timeline test, so the Timeline test is very valuable to give you assurance that the basic speed is accurate and maintained, but then we get into the dirty unknown. What happens in between at the micro level.
I have made a statement supported by physics that the high inertia of the Final will result in deceleration due to stylus lag variation of 1/4 in magnitude of that of the Technics SP10mk3 and Kenwood L07D. Furthermore results that quantified the stylus drag with and without the stylus playing are at a level less than the wow and flutter levels of the Technics SP10mk3 and Kenwood L07D.
A counter argument has been proposed that properly designed servo speed correction is a fundamental requirement for any TT. No numbers or empirical evidence have been put forward.
This is the nub - both the Final and the SP10mk3 are 2 of the best TT's made, they are at or near the top of the tree - so the question is what if you cant afford or obtain the top of the tree? What compromises should you make if you are going to make any ? Most think that what they have is the best. My nature is to try and understand why things sound the way they do. I have been able to improve my system by doing this - understanding what I have, its design construct and selecting products that achieve the goals which for me are important, speed, timing, coherency, harmonic structure. I personally dont have perfect pitch, but I'm extemely sensitive to timing - if the timing is off, I cant stand the music, fall asleep, lose interest.
The posts here that have references to gear I might have heard, hard facts are valuable and enlightening. Recent examples are Halcro's speed testing and Mosins' debate on belt creep which led me to study up previous posts and discussions on vintage idler motors, which was informative. Folk shouldn't get offended by posts - just get pissed off enough to go away and do some research. We all learn from this process.