Stylus-Drag..Fact or Fiction?

"Cogging is a function of the number of poles; the rotor experiences a regularly irregular rotational force due to the naturally varying intensity of the magnetic fields produced by the stator. The rotor is therefore constantly inconstant in its speed. There is a regularity to it that is said to be audible to some, and that's "cogging". The tendency can be ameliorated by using a stator with a lot of poles, the more the better."

This is only partially correct.  Cogging is caused by the change in variable magnetic reluctance as the PM rotor passes the metal pole pieces of the stator.  Adding more poles does not decrease the frequency or amplitude of cogging.  If you turn the motor by hand you will feel the cogging and it "feels" finer with a 24 pole motor vs a 12 pole motor because the cogs are closer together.  A 24 pole motor turns at half the speed of 12 pole motor so the frequency of the cogs is identical in both (120Hz).  The magnitude of the vibration caused by cogging will be identical in motors with identical power ratings and the vibration is directly proportional to the power consumed by the motor.  In most cases, the 24 pole "upgrade" motor is higher power than the 12 pole motor it replaces, so the 24 pole motor will actually produce more cogging than the 12 pole motor it replaces.  This was investigated in the link below:


https://www.diyaudio.com/forums/analogue-source/309925-hurst-motors-300-rpm-vs-600-rpm-upgrade-myth....


Coreless motors have no metal pole pieces in the stator windings so they produce no cogging.

Phoenix, Thank you for that explanation. Do DC motors cog at all?

Mike

Mike, Yes you have to ask for it and it will probably cost you an additional fee. Gabon ebony has a specific gravity close to 1. 1 is the specific gravity of water. So Gabon ebony is very stiff and heavier than most wood. Once it is dry it is also very stable. Great arm for Koetsu's and Air Tights. Problem with it is that it is rare and very difficult to dry. Usually you wind up wasting 30 to 40% of the wood in the process. Good Gabon Ebony is jet black. Black piano keys use to be made out of it. I use it for details in cabinets like drawer pulls, handles, inlay and such. It turns very nicely. 

Usefull information here.

https://www.rarewoodsusa.com/product/ebony-gabon/

"Phoenix, Thank you for that explanation. Do DC motors cog at all?"

Any motor with iron pole pieces will exhibit cogging.  In a DC motor, the magnets are stationary but the rotor coils are wound on steel laminates with poles which also produces cogging.

Some of the better BLDC motors have stators with skewed poles (angled slots rather than vertical) so the rotor sees more or less a constant magnetic reluctance and produce much less cogging.

But an AC synchronous motor could still exhibit cogging, if it is poorly designed with an inadequate number of poles.

But one should look at the rpm of such motors- instead of running at 33 rpm like a direct drive, 1800 rpm is common; at that speed cogging simply isn't a thing.  It becomes a thing when the frequency of the event is slow enough that it falls within the perceptual (time) range of the human ear.

By comparison the speed variation caused by a stylus totally dominates the field.

Most of the direct drive motors (at least the better ones) are coreless so they have no cogging. An 1800 RPM motor is a 4 pole induction motor; the stator does not have the poles and gaps that an AC synch motor will have. When you turn an induction motor by hand there is no cogging because there is no permanent magnet in the rotor. The rotor is magnetized by the rotating field, but that requires a certain amount of "slip" to operate and is a function of the torque load. Because of this slip, induction motors are not truly synchronous which introduces another variable in speed control.  Induction motors are speed sensitive to voltage as well as torque, where AC synch motors are unaffected by either.  DC motor speed is affected by voltage, temp and torque load.  As stated previously by others, there’s no free lunch and there are strengths and weaknesses to each design choice.


Stylus drag is fairly constant so in most cases, it is inaudible. While there is a measurable change in speed caused by stylus drag that varies from the start of a record to the finish, it is rather small and extremely slow changing and mostly inaudible. Changes in speed with groove modulation exist in theory, but I have never seen any data that claims to measure or quantify it; it must be extremely small. Heavy platters with lots of inertia will have a positive effect on this phenomenon, because changes in groove modulation are short duration (by definition) and more inertia will reduce short term speed variations.

In my experience, the biggest change in speed of BD tables is caused by the warming of the belt and bearing oil viscosity; it is not uncommon to see speed drift of 0.2~0.3 RPM over a 45 minute playing time which is audible to those with pitch sensitive hearing and if corrected all at once, audible to just about everyone.

While coreless motors exhibit no cogging, they do show, at a much lower level, perturbations in output torque. As designed and as built are two different things. 

Is this audible? maybe. What this wonderful hobby has taught me is that pretty much everything is audible, at least in the analogue world where I live.   

Halcro, Very few of us have perfect pitch and even those that do probably still do not have the resolution to hear the degree of slow down caused by stylus drag. Unless you have a table like the Monaco that can pick up speed changes in 1/72nd of a rotation there is little you can do other than set your turntable speed while playing a record. The drag (speed) is going to change across the record and with various frequencies and modulation thus the speed is going to vary fractionally. I would love to see how a table like Kuzma's Stabi XL DC performs with the timeline. I would hazard a guess that it does very well. I know for a fact my SOTA slows down a little just by using a strobe disc. Their new drive might counter that but it has lower resolution, 1 rotation. Will that be good enough? It should certainly do better. At any rate I can not hear changes in pitch that slight so does it really matter? Again to me the most important aspect of vinyl playback is noise. Not only can you hear it but it can also drive your subwoofers crazy particularly if you use room control. I have had several records that I had to return because the lath used to cut the master was in bad shape and the rumble was obnoxious, all Rykodisc I might add. 
Today is Yom Kippur and I would like to apologize to anyone I have pissed off last year:)  

Thank you Phoenix. What do you think is the optimum motor to use for a turntable?

From my experience, the highest performance for either belt drive or DD is a 3 phase BLDC motor with the caveat that it is run as a 3 phase AC synch motor and not a DC motor (they can be operated both ways).  If done right, they have little or no cogging, more torque than a comparable AC synch motor and the speed is determined by the frequency so speed control is fairly simple, though the drive circuitry is not.

Richardkrebs, I do not think there is much difference between analog and digital in that regard. There is just more stuff to deal with in the analog world. Staying purely in the analog world I think you rob yourself of some fine musical experiences. As an example, Jethro Tull's Thick as a Brick.
I have three versions, the original Album, the CD version and a remastered 96/24 download. In the CD version Ian's voice is cutting and uncomfortable at 95 db forcing me to use a notch filter centered at 3000 Hz. The album not so at all. Ian's voice is perfectly smooth. I just got the digital download and listened to it for the first time running the album in sinc at the same time volume matching with a meter. Ian's voice has a bit more bite than the album but not uncomfortable at all, but the download has superior bass and a better dynamic range so it is more punch. At the end of the first side I hear a squeak in the bass drum pedal for the very first time and I can not hear it in the other versions. Imaging is better in the 3rd dimension. Ian's flute and Martin's guitar float in space where on the Album an CD version they are painted on a wall.
Now much of this is probably due to the mastering but some is not particularly the dynamic range. Much less dynamic compression than on the album and CD. 
I'll go where ever the music is best. Sometimes vinyl wins the comparison sometimes not. This is also true for old analog recordings like Thick as a Brick. It is not just the modality. Other issues come into play. The only common denominator I have noticed is that digital recordings sound better in high res digital so I avoid newer recordings in vinyl. With older recordings recorded before 1980 vinyl is frequently better than the CD version. 
Sorry for getting off topic. But, In the end it is all about the enjoyment of music. Cool looking equipment is no good if it does not sound right.
Some systems will tilt the analysis for instance in a system that is a bit dull the CD version of Thick as a Brick might sound better. And so you get variations in opinion not due to different hearing. Different systems.
When I do these things with friends present more often than not we come to exactly the same conclusions. Don't give up on digital. There is a world of great music there. The only problem is that there is no equipment there that is as fascinating as vinyl playback. 

Mike

In my experience, the biggest change in speed of BD tables is caused by the warming of the belt and bearing oil viscosity; it is not uncommon to see speed drift of 0.2~0.3 RPM over a 45 minute playing time which is audible to those with pitch sensitive hearing and if corrected all at once, audible to just about everyone.

That’s why I’ve always turned my SDS on first and had my BD TT spinning, while the system’s electronics/tubes warm up, B+ stabilizes, etc, for about an hour.  Then there’s that 0W-20 Mobile 1, in the VPI’s bearing.  I figure; every little bit helps!

Phoenixengr, that would involve using a sophisticated solid state 3 phase converter plus the electronics to control speed. I can just see people getting a rotary converter with their Turntable:)
Rodman, use Millers racing oil. It has nano particles in it that reduce friction another 25%.

richardkrebs
Is this audible? maybe. What this wonderful hobby has taught me is that pretty much everything is audible, at least in the analogue world where I live.

Hi Richard 
Based on my personal experiences with the Goldilocks adventure, room dimensions,and specifically, the narrow rectangle  - shooting down the short wall, and the type of pickup tonearm/cart used, has "very much" to do with how much is "audible" 8^0

Dear friends: I would like to know if each single LP was recorded/cutted at exactly/accurated 33.333..rpm and if for any reasons exist tiny deviations from 33.333..rpm accuracy why or how can we or not detected through an accurate TT that spins at exactly 33.333...rpm during play time of LPs? 

I think that some one can put some light about.

 The stylus-drag is a fact and can be fixed but those tiny differences in speed/pitch always comes by speed non-accurated TTs or by the LP it self?

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Phoenix, Thank you for embellishing on my response to Atma-sphere re my point that operating a motor with 3-phase AC synchronicity does not per se eliminate cogging.  I am a rank amateur on this subject with only a good college level background in physics (and a lifelong habit of thinking like a scientist).  But I was a bit puzzled by your statement: "A 24 pole motor turns at half the speed of 12 pole motor so the frequency of the cogs is identical in both (120Hz)."  In a direct-drive turntable, doesn't the motor have to turn at 33.3333 rpm, regardless of the number of poles?  And therefore might there not be a theoretical advantage to having double the number of poles?

Oh, and thanks for clearing up the many ambiguous on-line websites that don't come right out and say that coreless motors are free of cogging.  It makes perfect sense (and I think I hear the benefits), but you'd be surprised at how poorly this subject is addressed and explained. (Or maybe you wouldn't be surprised.)

Raul raises a good point. How accurately are the various cutting lathes spinning? This is a whole different topic. 

It does lead nicely into long term average speed accuracy....
There is a trend to show how incredibly accurate peoples DD TTs run, posting videos using the timeline over extended runs. This is a great demonstration of how accurately a TT's long term speed control can be.

But how important is an average 33.3333333 rpm?
Lets say TT1 runs at an average 33.333 and TT2 runs at an average 33.334. A 1000hz tone cut accurately at 33.333 would of course be played back at 1000hz on TT1, but it would be higher on TT2 at 1000.03hz.
I don't claim to be able to hear this difference. 

What I think is important is the TTs dynamic speed accuracy. How does it behave under a varying load. I believe that we are sensitive to real time changes in pitch. But do not hear them as such. Halcro describes the Raven as being more relaxed than the Victor. This general description pretty much covers many BD/DD comparisons. Clearly we are hearing differences but not describing these in terms of pitch. We  use different descriptors.. 

The timeline only tells us how long it takes for the platter to make one rotation. Confirming, or not, that it took 1.8 seconds at its 33.33 setting. That is, was its average speed 33.33 or not.  It does not tell us anything about what happened to the platters dynamic speed during that rotation. 

Yeah, yeah, the platters inertia will save you, I don't think so. There are no free lunches.  


Chris.

Many thanks for the input of which I completely concur.


Lewm
I couldn't resist!  

Dear @richardkrebs  :  "   This is a whole different topic. ", yes diferent but with direct relationship with " audible "/or not speed deviations that we " charge  " to the TT culprit when maybe not always came from the speed unstability in the TT.

Perhaps we need a recording engineering to answer the question, that I remember in this moment Atmasphere has enough experience about and maybe he could chime here on it.

In the other side:  "  TTs dynamic speed accuracy. """ M.Lavigne posted about " steady " as the critical issue and yes this is the main subject with any TT.

In your example if both TTs are " steady " we can't be able to detect it and maybe we can't even if not steady because speed difference is so tiny.

R.

"But I was a bit puzzled by your statement: "A 24 pole motor turns at half the speed of 12 pole motor so the frequency of the cogs is identical in both (120Hz)." In a direct-drive turntable, doesn't the motor have to turn at 33.3333 rpm, regardless of the number of poles? And therefore might there not be a theoretical advantage to having double the number of poles?"

My statement was in response to the assertion that adding more poles reduces cogging (it doesn't).  Doubling the number of poles does not change the vibration signature because it will also cause the motor to turn at half the speed (assuming the same 60Hz drive signal).  Both a 12 pole and a 24 pole motor will produce vibration from cogging at 120Hz (10 revs/sec x 12 poles at 600 RPM  and 5 revs/sec x 24 poles at 300 RPM).  The amplitude of the vibrations is directly proportional to the power consumption of the motor, not the number of poles.  If you go to the link I provided, you will see that the measurements bore this out.

The motor on a direct drive table does turn at 33.333 RPM so the number of poles will determine the drive frequency needed in that case (RPM=Freq x 60/pole pairs or Freq=RPM x pole pairs/60).  If the motor uses steel pole pieces, it is subject to cogging and the frequency of vibration will be 0.555Hz x number of poles;  in most cases, this would be below 20 Hz so it will show up as rumble.  To run a DD motor from 60Hz would require 216 poles.


From what I've seen, most of the DD tables use a DC motor with servo control (feedback) to maintain proper speed.  This of course, comes with its own set of problems.

Audiophiles are strange.

It is obvious that adults can’t develop perfect pitch (see why), so most likely none of you can detect such a tiny difference in pitch/tone by ear in a blind test playing records on your turntable. Even professional and very well educated musicians does not have a perfect pitch. How to develop perfect pitch? Watch this. I found it very interesting.

If you could detect a difference in tone between 33.333 and 33.334 then you’re not a human, or you must be 1 of 10 000 people trained for a perfect pitch since you’re baby.

In other words: If your turntable spinning slightly faster or slower you can’t detect it anyway when it comes to such a tiny difference people describing here above.

C’mon: 33.333 or 33.334? Are you serious?

Only 1 out of 10 000 people might have a perfect pitch and the only reason for this is because they’re born in a family of musicians and they were trained in the first 4 years of their life. Just watch this video.


P.S. I am using top japanese DD turntables with two tonearms on each and all those DDs are stable as hell.

Stylus-Drag ? Even if the tracking force is 1-3g, how about 900g record weight we’re putting on top or the record each time we play it? "Stylus-Drag problem" does not exist for me. Happy listening.

chakster.

I said... "I don't claim to be able to hear this difference"

You seem to be agreeing with me?.

"Dear friends: I would like to know if each single LP was recorded/cutted at exactly/accurated 33.333..rpm and if for any reasons exist tiny deviations from 33.333..rpm accuracy why or how can we or not detected through an accurate TT that spins at exactly 33.333...rpm during play time of LPs?"

The most popular motor for the cutting lathes is a Technics SP02 direct drive motor which is quartz locked for speed accuracy and weighs ~110lbs with plenty of torque.  W&F are rated at 0.0084% RMS.  In terms of absolute speed accuracy, it should be more accurate (and more stable) than most of the DD tables playing the LP it cuts.

http://pspatialaudio.com/lathes.htm

of course, this is a natural selection problem. far beyond numbers or instruments. my son-in-law is a physicist working for the Allen Institute. they do brain research. he assembles big data for the neuroscientists.

he said in maybe 10 years they will be able to replicate a cubic cm of mouse brain tissue. but right now it’s too much data to replicate. he does not think he will live long enough for them to be able to do that for a cm of human brain tissue. just too much data.

so when we think that we can measure what our senses have evolved to sense, we are kidding ourselves. and not just the hearing part. the whole body is involved in whether we think something is fake or real.

which is why getting as close to absolutely steady as possible means more to our musical sensibilities than what we view as corrected speed. there are no naturally occurring servos.

In general, accurate rotation is obtained by servo-control by negative feedback, but at the micro level, if it rotates or becomes faster, it detects it and slows it, and repeats the operation to make it faster if it gets slower. If you try to measure a period with a small level, you cannot measure the instantaneous state, so you should measure the average value. Therefore, fine vibration generated by servo-control cannot be measured by the measuring instrument, it depends on the human ear.

Mike.
Exactly. This is what I was trying to say with respect to dynamic speed stability, (steadiness)
The level of granularity we use to measure TTs is simply too crude to show us what is going on in real time under dynamic conditions.  

But we sure can hear it.

Hi @lewm.

... No matter how much I search on that last topic, I have never found a satisfactory treatise on the subject of coreless motors vis a vis cogging, but most talk about coreless motors as if they are free of it. ...

Here's a few links that may be of interest;  cannot say if they count as satisfactory. 

Comparison of Slotless and Slotted Motors. The article does discuss cogging.https://www.celeramotion.com/applimotion/support/technical-papers/slotless-vs-slotted-motors/

Brushless, slotless, and cogless (1999)
https://www.designnews.com/content/brushless-slotless-and-cogless/60538412940113

Very interesting thread.  As I read through these responses, I have to wonder if the original recording mechanism, the record lathe that cuts the master from which the molds are made, is equally subject to modulation induced speed variations.  Plowing a new field, so to speak, would seem to take a bit more energy than playing an existing groove.  How does the record lathe overcome this?  And if it doesn’t, perhaps stylus drag speed variation in the playback system mirrors the speed variation in the recording process........

I started a thread years ago inviting people to upload videos of their turntables with the Timeline.  Lots of promises but no one took me up on the challenge.  Here is a link to that thread:

https://forum.audiogon.com/discussions/turntable-speed-accuracy/post?highlight=SME%2Band%2BSutherlan...

Here is a link to a video of my SME 30/12A with the Timeline:

https://www.youtube.com/watch?v=Clwc_c8sVn0

Look for the red laser dash on the edge of the LP cover.  It is not perfect, as you can clearly see the quality of the laser dash changes slightly indicating micro speed fluctuations, but it is pretty good.

I also made a video using my friend's Technics SP10 Mk3 with the Timeline:  https://www.youtube.com/watch?v=haqhT6khqZY

Great performance, but when we moved that table into my system and compared its sound to my SME 30/12A using the same arm and cartridge, the SME sounded much more natural and like real music.

The belt v. DD debate will go on for a long time.

’Very interesting thread. As I read through these responses, I have to wonder if the original recording mechanism, the record lathe that cuts the master from which the molds are made, is equally subject to modulation induced speed variations. ’

@pickindoug- Phoenixengr addressed that exact issue, just four posts before yours.

^^^^  up 2 posts

@peterayer 

Peter
your findings were very interesting (One table short of a Goldilocks adventure.) 

Your findings are supported by what Richard said.

richardkrebs
The level of granularity we use to measure TTs is simply too crude to show us what is going on in real time under dynamic conditions.

But we sure can hear it.

Still

IMO, based on my personal journey, "Stylus Drag" is not an Iceberg Scenario, where most of what is happening is below the surface; where this thread is focused.  The table and keeping speed. 

What is happening above the surface is just as, if not more important in regards to Stylus Drag, since I believe the type of cartridge and tonearm pickup used are worth ........hmmmmm..........let's call it 33.333 % each. 8^0

As we know playing vinyl properly requires good setup between the trio of parts.
Cheers Chris

Peterayer, no big surprise. The 30/12 is an amazing turntable. It's degree of isolation is better than any turntable I am aware of. The V12 is IMHO SME's best tonearm. Have you checked your resonance frequency on a test record? The SME is the lightest 12" tonearm I am aware of. It's effective mass is only 12 gms. The Air Tight is almost as stiff as a Koetsu.
My guess is that adding some weight to the head shell might improve your bass a bit. I set mine up for between 8 to 10 Hz. 
Guys, chakster has a very valid point. Speed variation is just not a problem for modern turntables because we can't hear it. This is just a spec war. Same goes for lathes but they have to be a lot more powerful and stable because the cutting head causes way more drag and variation in drag than a stylus running in a groove. The big problem with both lathes and turntables is noise particularly rumble which is not only very audible but you can see it!  Just look at your woofers dancing around wasting amplifier power and Doppler distorting everything else the woofer is doing. All our preamps use to have rumble filters, just high pass filters 3 dB down at 30 Hz. As I have mentioned in previous posts it is not uncommon for a poorly maintained lathe to rumble. I have had several discs that were so annoying I sent them back. The ones I sent back were all 180 gm "Audiophile" pressings and all were Rykodisc. I have many records that rumble a bit but not so bad that I can't listen to them. I have never been bothered by speed variation and none of the audiophiles I know have complained about it. I think that probably only rapid speed changes would be audible but our heavy platters just can't change speed that fast

The 30/12 is an amazing turntable. It’s degree of isolation is better than any turntable I am aware of.

while the passive isolation for the 30/12 from all those rubber bands is relatively effective, it is limited. OTOH the overall build quality of the 30/12 results in top level sound, but the isolation component is relatively pedestrian. i think maybe Peter has his 30/12 on a passive air decoupling Vibra-plane platform to improve isolation. that is degrees better than the stock 30/12 isolation, but still passive.

for ultimate turntable isolation you need to observe how science does isolation. they use active shelves with piezo-electric sensors and actuators in 6 axis’s.

http://www.herzan.com/products/active-vibration-control/ts-series.html

as it comes stock for science this product is not fully ready for high fidelity purposes. it has a SMPS which broadcast’s noise into your signal path, plus it’s limited to effectiveness under 200hz so needs further modification to cover the whole FR. and as it cannot discern the source of resonance it attenuates, only tt’s with very low self resonance work well with it. but properly modified and applied to the right turntable it takes things where no passive isolation approach can follow.

I THINK that some of us are saying this:  Absolute accurate speed is not the issue.  I (and whoever) would agree that I am not able to discern the difference between 33.334 and 33.333.  In fact, I know for sure that I cannot tell 33.333 from a constant 33.5 or from 33.2, because I can do that experiment with the Phoenix Engineering Eagle and Roadrunner driving my Lenco motor.  What IS potentially audible are VARIATIONs in constant speed, drifting of speed during musical passages especially that feature piano and/or stringed instruments.  Whatever technology used in turntable design and build that eliminates or minimizes speed instability (DD, Belt-, or idler-drive) is fine with me.  It just so happens that for me the best vintage Japanese DDs and my Lenco do it at lowest cost or best bang for the buck.  Belt-drives at anywhere near the same cost have failed, speaking for myself.

Mijostyn, Those rumble filters may be useful if you hear rumble, but in all other cases, they are no free lunch.  The filter elements color the sound all the way up the scale, inevitably.  I also don't know where you are getting your LPs from, but I rarely encounter rumble that is problematic enough for me to want to engage a high pass (rumble) filter.  This is using two completely different audio systems in my home environment, driven alternately by 5 different turntables.  I'm not saying "never", but it's rare.

The most popular motor for the cutting lathes is a Technics SP02 direct drive motor which is quartz locked for speed accuracy and weighs ~110lbs with plenty of torque.

I doubt this statement. It implies that there are more lathes using the Technics motor (which is great) than those that don't. The simple fact is all lathes unless custom built are vintage machines. Mine is typical- its a Scully built about 1948 or so, equipped with a Westerex cutterhead and electronics from about 1970 (refurbished). The lathe portion didn't see much change over the decades until Scully ceased production altogether- the big change was how the cutter head was advanced across the LP (IOW, when variable groove spacing was introduced) not how the platter drive operates.

To that end, the platter is driven by a drive shaft operated by a transmission that has the gear ratios for its two speeds (33 and 45), which is in turn driven by a 1/8th horsepower synchronous motor running at 1800 rpm. The motor, if operated with no load (or external flywheel), takes over 30 seconds to spin down (nice bearings). That, coupled with an external flywheel and the various bits of rotating mass in the transmission as well as the actual ~17" platter, insure that the platter's motion is very constant. In a machine such as this, the proper function of the drive shaft and whether the platter bearings have been properly lubricated and warmed up (the manual calls for a 20 minute warmup time) has a much greater effect on the platter speed stability than any 'cogging' that might be present in the motor!

Scullys were one of the most popular lathes in the US for a long time, but there are other types such as the Neumann as well. Except for those that use the Technics drive motor, they all run along similar principles.


I've used the Timeline on the Scully; when we were finishing the refurbishment a few years ago I felt it a good idea to see how we were doing. Its pretty stable- but IMO isn't the last word in speed stability or accuracy. It can keep a strobe absolutely still and doesn't vary except when the cutter head touches down to do a cut (which runs about 60 grams of pressure on the stylus). Once touched down the strobe stays put. But the Timeline tells a different story- essentially that the lathe  runs ever so slightly slow. How much I've yet to determine since I've not set up the Timeline to present a calibrated assessment. But its clearly close enough that hearing a pitch variation is impossible.


IMO, the big issue of stylus drag affecting speed isn't pitch stability so much as it can induce oscillation of the arm over the stylus- in turn causing the tracking pressure on the groove wall to vary left to right and back. As that happens, it induces to my ear a slight 'shimmer' in the soundstage; when you have a 'table that has really locked-in speed, that shimmer is gone and the soundstage is like that which you hear in reel to reel tape.

back years ago when i switched from my Basis belt driven tt, and belt driven Rockport Sirius II SE, to the direct drive Rockport Sirius III turntable; the most obvious ’stylus drag’ thing i heard was lack of clarity and coherence on large musical peaks. you would get a hardness and lack of cohesion with those belt drive tt’s.....absent with the DD Sirius III, then later the Dobbins SP-10 Mk2, then the Mk3, and then the Koda ’The Beat’ and finally the NVS. yes; piano sustains also could be an issue too. but for me, a lover of big music, it was how those belts handled the peaks that bugged me. you assume that distortion is in the recording....and then hear it sound absolutely right and do the head slapping thing.

which is not to say all belt driven tt's are equally vulnerable to that malady. i know some are not. but it has to be overcome somehow as it's inherent in the approach.

@phoenixengr

From what I've seen, most of the DD tables use a DC motor with servo control (feedback) to maintain proper speed. This of course, comes with its own set of problems.

Would you kindly lay out what the main problems are?

lewm
I THINK that some of us are saying this: Absolute accurate speed is not the issue.

I learned how important speed stability was, over the actual speed when I was 10 years old. Got my first - to me - portable stereo - Hitachi am/fm with cassette and microphone.

The next few days I filled one tape - recording music from FM.
When the tape was full, I played only my tape of music for the next week. I remember to this day thinking what freedom I had to play my own songs. Of course I had taped songs that triggered a "happy mood" in me.
Life was good.     

************************************

After one week, I switched to, and listened to FM radio again. Something was wrong. I noticed that the songs I had recorded now coming at me through FM, did not sound as good as my taped version. They sounded slow and lethargic. I was confused. My tape version of the songs had a better tempo, more energy. More life.

Sometime later ....I figured out what had happened.

***********************************

The tape motor in my stereo was running fast. Oh... it was a stable and consistent enough speed, so it sounded ok. It was just running a little fast.
I learned at 10 years of age that "Speed Stability" is what is important.

Sometimes I like to speed up my turntable, up a bit, you know ....go audiophile crazy.... just to hear older female voices ...........sound younger.

Fountain of Youth ?  Try that with your digital. 

A key to reducing the effects of stylus drag is reducing turntable bearing friction. Ultimately,  the effects of drag all go back to the motor.  If it has less work to do overcoming bearing  friction so much the better.

Chris
You took the words from my fingers sir!

I routinely run my TT,s and my R2R ever so slightly fast deliberately just for that sense of extra attack, drive and dynamics.
Correct?
No but it's my system and ears and stability is key for me NOT absolute speed being locked at 33.333333 recurring.
Heck if it was good enough for Fleetwood Mac it works for me.

Anvil, any added friction is going to slow any table down a bit unless it has a compensatory mechanism. Most tables create an equilibrium situation which in table like the big Kuzma is probably strong enough to overcome stylus drag. In some tables like the older SOTAs you can adjust the equilibrium with the stylus down but the table itself is not compensating. This is not the case with the new ones. The Monaco is fascinating because it's resolution is so high but it is direct drive and unlike mikelavigna I do not like big magnetic things under my cartridge.

mike, there is such a thing as "carrying it to far." Why don you just stick your turntable in an isolation camber so airborne vibration doesn't get to it? I bet if you sit on one of those tables your hearing will improve:)

Ralph, What are you doing with a lathe? Atma-Sphere going to start making records? 

Mike

IIRC, Ralph has made a number of records.

mike, there is such a thing as "carrying it to far." Why don you just stick your turntable in an isolation camber so airborne vibration doesn’t get to it? I bet if you sit on one of those tables your hearing will improve:)

in a thread about ’stylus drag’ you are complaining about ’carrying it too far’? really? i think any participants in this thread would be considered by non audiophiles as ’carrying it too far’. it’s what we do here.

i will shamelessly admit to likely being at the far end of the ’carrying it too far’ bell curve.

i have 5 of those modified active platforms in my system; under both of my mono block amps, under my preamp, under my dac, and under my turntable. they are awesome tools to eliminate resonance. the musical connection they allow, especially when the music gets very dynamic and soars, is worth it. you can see pictures of those platforms if you look at my system page.

'carrying it to far. i'm the poster boy for that.

Very nice looking system Mike!

Those platforms are indeed impressive.

OK, enough BS about setting RPM with or without a record being played. Any decent TT has one of several motor-speed control methods to lock-in on or close 33 1/3 (or 45) RPM. Having arrived at "any" RPM setting/value the motor-speed-control compensates for stylus drag or lack thereof. That's why its referred to as speed-control. The Raven exemplifies the precision of its "speed-control" in the video. Because the laser point "changed position" due to stylus drag or lack of is only proof of its existence for that brief interval before compensation is made. If the RPM be exact the point after negative feed back should remain steady which it does. Because it has moved to right or left is not an argument but holding steady under varying loads is testimony to the TT's motor-speed-control's accuracy. The beauty of the Timeline is to allow you to set the Raven's RPM as close to 33 1/3 as possible and doing so with or without drag is BS. Video shows the laser point holds rock steady 33 1/3 RPM under all conditions including no drag. If the point moves with each subsequent revolution of platter it indicates other than a 33 1/3 RPM but says nothing of the TT accuracy of holding a desired higher or lower RPM setting. That's what's important.The timeline is nothing but a clock flashing every 1.8 seconds. Stick your finger on platter and you change laser point position and MSC should keep it steady where ever this dot ends up. Because the dot has changed original position only indicates a sudden load event has occurred. If perfectly set at 33 1/3 and dot is stationary after initial load change dot on wall will remain at position. A movement of dot merely indicates other than non attainable perfect RPM which isn't the most important thing here.

The simplest way to correct for stylus drag is to play a test tone, say 1000 Hz, then adjust the speed of the turntable (if adjustable) until the frequency read-out on a frequency meter reads 1000 Hz. A good Fluke meter with frequency read-out will do nicely.  There may be a different drag for different frequencies, but setting it for one frequency seems about the simplest solution.

Mijostyn , you are looking at it from the wrong angle. Added stylus friction is inevitable but the system can be optimized to best deal with it. Lowest possible bearing friction is part of that puzzle. Low friction bearing make even small motors look huge .A heavy platter helps but rpm  ultimately  goes back to the motor and how its coupled. 
Regarding magnetic  forces under a platter or cartridge  it is irrelevant if the TT is designed for it. Shielding a magnetic force is easy although  not always inexpensive. 

Mike then we agree, knock yourself out. I'm sure it is a lot of fun for you. I would rather spend my limited money on stuff that would make a substantial difference like ear plugs for my wife:)
Anvil, stylus friction is going to have the same effect regardless of bearing friction. A system with more power and inertia might not be effected as much. How the motor is coupled makes no difference. Pulsating magnetic forces under a very sensitive magnetic device is just asking for it. This is the reason most of us think direct drive tables sound terrible. I am certainly one of those although I am always open to new designs like the Monaco. There is no reason to even go there. Any improvement in speed accuracy over a good belt drive table is inaudible. It is easier to make a silent bearing if you do not have a motor wrapped around it and you do not have to worry at all about stray magnetic fields as the power of a magnetic field drops with the square of the distance. 
Guyw3, that would certainly work but is more difficult to set up. Most of us just throw a strobe disc on the record while playing and set the speed while the record is playing. 

Dude, quit while your behind :)

uberwaltz
I routinely run my TT,s and my R2R ever so slightly fast deliberately just for that sense of extra attack, drive and dynamics.

Hi Kevin 
I know a guy that actually likes the speed a little slower.

Some of my fondest music memories are of listening to music groups/bands in nightclubs on a regular basis, before the whole marriage/kids, and lack of time ....
The tempo of the performance was never the same, night after night from same bands. In fact it seemed to me that the tempo for a specific night was set, based on the state of how the drummer showed up. *^)