Turntable speed accuracy


There is another thread (about the NVS table) which has a subordinate discussion about turntable speed accuracy and different methods of checking. Some suggest using the Timeline laser, others use a strobe disk.

I assume everyone agrees that speed accuracy is of utmost importance. What is the best way to verify results? What is the most speed-accurate drive method? And is speed accuracy really the most important consideration for proper turntable design or are there some compromises with certain drive types that make others still viable?
peterayer
The Timeline is giving you one data point per rotation. So what is happening in between those 1.8 second pulses? Your ears just told you something more is happening than just precise timing of the platter. It is like peeking into the room and everytime you see the cat sleeping, but still the canary disappears. The timeline is giving only one dimension of speed control- ie. timing of the rotation period. What is happening during the rotation? The platter could be cogging, it could be wobbling or even have Wow due to an out of round pulley or out of round platter OD.
Beyond the speed accuracy measured by the timeline, as someone else mentioned, speed precision is also important. That means how well does the platter hold 33 1/3 during the entire rotation. This has to be measured either with a test record or with a precision tachometer. The best instrument might just be our ears. Test records have limitations- the accuracy of the center hole in records causes them to be at least one order of magnitude worse than most turntables. (Two order of magnitudes worse than Halcro's DD turntable.)
Halcro, great info and thanks for sharing. What you have mentioned has left me scratching my head and always learning.

I know "D" is a little occupied presently but hop he will be able to assist adding to this.

What Tony has mentioned above is another perspective but in referrence to out of round pulley or platter doesn't make any sense to me in relation to yours specially reading what you have experienced.

You have three motors so why not do what I had mention earlier in one of my previous threads.

Place one motor off to the left using your thread and then place another motor off to the right using a separate thread attached but only have one motor working, this will do what Dover mentions above acting as a flywheel and balancing the platter.

When I had my AC3 and spun the platter with no pulley attached it would revolve many times but did slow down fairly quickly but with my Black Knight it's appears to be totally different. Spins allot easier initially and keeps spinning consistantly for a lot longer time prior to actual slowing down, to me this was very interesting in a positive way.
Dear Dover: About thread/high mass platter my AS are not really high mass ( I think are around 12-14kg ) and works really fine with thread and the RX500 performs good as well. Yes, maybe different TT design works different but I can't see very clear the whole reasons about if there are some reasons.

Regards and enjoy the music,
R.
The platter also does not keep rotating very far after the motors are switched off indicating perhaps a bearing designed for friction so that the motors have a load against which to pull?

Halcro, I can't think of a reason for a bearing to provide drag in a turntable- that seems like a Bad Idea to me. Are you sure the bearing is OK?
Use of a capstan, etc, or any strategy that increases the area of contact between the belt and the platter is a good way to combat "belt creep", the bete noir of belt-drive tt's. This is why I am skeptical about 2- and 3-motor arrangements; of necessity, the platter to belt contact area is reduced in both cases, even compared to conventional single-motor arrangements. This is also why I really like the Artemis SA1 turntable, in principle. (Never heard it.) It uses a single motor and a capstan so that the belt (looks like tape) is nearly completely in contact with the circumference of the platter.

Dare I say that a device like the KAB might be superior to the Timeline for detection of very transient deviations in speed? OK. I said it.
Halcro, I can't think of a reason for a bearing to provide drag in a turntable- that seems like a Bad Idea to me. Are you sure the bearing is OK?

What style bearing is in the Raven? I remember reading about it some time ago... something about it being oil-less or not having an oil reservoir or something like that. Halcro?
There are a couple of different bearings used in this table, the latest version being different and older versions not upgradable. Well you could but you would also need a new platter.

The bearing in the BK has what looks like a ball bearing on the top.
Dear Halcro: You always can try a different thread's build material and see/hear what happen.

regards and enjoy the music,
R.
Halcro - great game eh. Looks like Dokovich has shown the others how to beat Nadal - ie hard and flat if they can maintain it.

Re the bearing, it's a bit of a red herring - I only meant to communicate that in the case of the Final there is high inertia such that if the motor is turned off and the belt/thread is still connected the platter will drive the motor/pulley for a few seconds.

Lewm's capstan is a good observation, the thing that interested me was that if you add a capstan and get more belt/thread on the pulley & platter it will spread the side loading on the bearings of the motor & platter. This would potentially reduce motor bearing wear.
Lewm,

That is a good point about belt contact with the platter. My SME 10 has about one inch of exposed/free belt before and after the motor pulley leaving the vast majority of the belt in contact with the platter. This is in great contrast to some other designs which have a motor on a remote platform 9" or more away from the record platter. Tables like the Walker, the Raven and the Micro Seiki all have a lot of exposed/free belt which is why some owners have switched to thread, I think.

I have not tried the Timeline on my SME or read of anyone else doing so, but the SME tables have a reputation for having pretty constant speed stability and accuracy.

I started this thread a while ago, and I appreciate all of the contributions to it. I have learned a lot. Thank you to all those who have participated.
Hi Peterayer,

I had mentioned in the NVS thread I had tested two and both were off. Using the same TimeLine it was found one was too fast and another was too slow.
Hello Dev,

Yes, I had read that now deleted NVS thread, but I forgot about your particular post. Do you remember how far off the speed was for each of the tables?

According to my KAB strobe, my SME is 0.18% fast, as determined by the fact that four (4) "33" numbers drift out of the red strobe light during a 1 minute test. This was while a record was playing. Unfortunately, my SME motor controller does not have a speed adjustment, so I change belts after about one year and that reduces the error.

I would guess that if you found one SME table too fast and the other too slow that the belts were probably stretched to different degrees. Were these models with adjustable speed on their controllers? If so, did you try to adjust the speed on the controllers to get a more accurate speed? Also, did you listen to each to see if you could hear a difference?
The concept of "belt creep" and what to do about it is not mine intellectually. This phenomenon was first described to me and to anyone else who read it by Mark Kelly. Mark played at designing a bd tt to combat it. The Artemis is a less complex solution compared to Mark's, IIRC. But your SME is well designed, Peter, if it places the motor pulley as close as possible to the platter's edge. Notts recommend this also. That also is a way to maximize the contact between platter and belt. You BD guys should look for posts by Doug Deacon on "tape drive". Doug uses a specific kind of recording tape which he then treats chemically to make one side rough, so it has traction on the platter. Conceptually, this should be better than string, IMO. Reality is sometimes different from concept, however. But Doug claims excellent results with his Galibier turntable.
Hi Ralph,
Belt drive turntables differ from one other in belt compliance and platter moment of inertia, so their oscillation wow patterns differ. That explains in part why belt drive turntables sound so different from one another in pace and rhythm, in steadiness of pitch, and in solidity of bass (bass notes last longer, so they require a longer sustain of turntable pitch accuracy to sound straight and massively impactive, rather than warbly, wobbly, and weak).
Can the belt drive designer reduce or damp the unwanted oscillations between platter and belt? In principle yes, but in practice it's tricky to execute. In principle, what's required is simply the addition of some resistive damping. This would damp the reactive LC tank circuit of belt and platter so it would no longer oscillate.
A common form of resistive damping is friction. Thus, if a knowledgeable turntable designer wants better speed constancy, he might well consider intentionally adding some friction to his rotating platter. It's worth noting that some Swiss and German engineers are so justifiably proud of their ability to produce nearly frictionless bearings that they cannot bring themselves to make turntables with high friction. As a result, the Thorens turntables exhibit some of the most spectacularly low friction bearings on the planet, and will spin seemingly forever (with the belt removed); but, at the same time they also exhibit some of the worst audible wow, in part because there is, as a matter of engineering pride, almost no resistive damping for the oscillating reactive tank circuit.
What might be useful ways to introduce friction? The fit and/or finish between platter spindle and well could be made poor, instead of smooth and polished. But this would be causing friction via crude irregularities, like two meshing mountain ranges, rubbing each other. The crude irregularities of these two mountain ranges rubbing together would cause unwanted speed irregularities (snags and letting gos), as well as unwanted vibrational rumble (the earthquake rumble of each letting go after each snag). So that tactic is out.
One useable tactic is to introduce a viscous fluid in the bearing, which provides friction in a liquid hence smooth form. This can be especially effective if the spindle is made in a larger than normal diameter, so that the viscous fluid has a larger moment arm (more leverage) with which to work its resistive magic (as in the Linn Sondek). The use of viscous fluid for resistively damping platter rotation can also be enhanced by various helical screw kinds of arrangements, which force the fluid to do extra work in opposing the rotation of the platter (as in the turntables from Max Townshend). It's no accident that these two brands have the best reputation among belt drive turntables for pace and rhythm, solid bass, and master-tape-like clarity. It's because both these designs recognize that belt drive, far from being a simple Hail Mary solution, brings with it new problems that must be addressed, and that overcoming the problem of speed constancy requires at least the addition of a fourth element, resistive damping, to the three usual elements of a belt drive turntable.
That's a quote from Peter Moncrief's incisive article about turntable speed control.
As also described in his article....is the fact that a 'stretchy' rubber belt can iron out the 'pulses' of a poled motor whereas if a non-compliant tight thread were employed........we're back to transferring that cogging into the platter?
Same model as yours which was also too fast ironically, the other table was a 30/2 and was too slow but when we put it on 45 too fast.

Owners were not very happy! specially when they thought it was set up correctly.

What do you do if you have no adjustments or worse the adjustments still don't allow you to get it accurate?

Not one table that I have tried has been spot on including my own with both speeds initially, some were really bad, mine wasn't but I learned that most could not be corrected either, mine was so I was lucky.

This TimeLine tool has assisted providing information that using other tools to set-up really to me are misleading but worse that manufactures are not paying close enough attention building their products.

So mine being off slightly, once I got it spot on I really could not hear nor feel the difference but on others I most defiantly could hear improvements if they were off badly so this is a postive tool to use and will be used in the future by me.

I recently went into a store whom I know the owner but will not mention the name and has some mighty exspensive tables and not one was spot on, he basically dismissed the use of the TimeLine saying they have all been set-up properly blah! blah!

I asked him if he did not mind to allow me to get one set-up using the TimeLine and then have a listen afterwards, it's not hard to do if there is a fairly accurate fine speed adjustment allowing such but the table also must be capable of doing such and this table was pretty darn close in the end but originally off pretty bad and this room we are talking big dollars.

I was told the rep was by the week prior and saying how sweet things sounded, humm!

When we were in the room he was tapping his foot and I said straight up are you for real, sorry but I'm not feeling it and this is a pce when I play at home my whole body gets into it and I just want to get up and boogie.

No way would it have me opening up my wallet but after using the TimeLine the sound was now locked in, the focus was way better, all arround just sounded different in a positive manner and just felt better if you know what I mean in a good way.

He came into the room and without even sitting down said he was already experiencing the difference so guess who will be getting a TimeLine to use.

Still did not leave me feeling the way I expressed above listening in my own place.

Personally I feel acurate table speed should be the basics of a table design, the foundation and then you go from there. If you can't get this right well ... I feel something is just wrong.
Hi Lewm,

but using a mylar belt has it's own issues. Static, dust attracts to it, they only last so long before slippage occurs. You have to spend some time makeing them up all the time etc.

Sorry but I just want to listen to music and not be dealing with that.

I also tried on a Lenco, won't mention the seller but it was also off. I inquired about this and basically got back a answer that it's fairly close. hummm

I tried it on a "DD" SP10 MK2 and it was off, no way to correct like the MK3 offers speed adjustments so the owner has to send it in.

Albert I had asked you about your NVS, I'm sure you have checked it.

Can you tell us the results.
Unfortunately bringing the motor closer to the platter also brings it closer to the cartridge as well. Which on the TT's I have had with that arrangement caused hum on most of my cartrides. There may be some TT's that sheild the motor well enough to pull it off.
The comment about using viscous drag or friction to dampen platter oscillations on bd tt's struck me. I do my own maintenance on my Sota tt. It is easy enough to disassemble the platter, clean and relube the spindle and bearing. I let it go for a few years and then about two years ago, I got around to pulling it apart and relubing it. I noted then that the tt sounded better, but I didn't really understand why. So now I clean and relube it every year. Some other Sota owners have also mentioned they found some synthetic lubes make it sound better than other lubes. I tried some synthetic lube last Fall and didn't notice a big difference in sound myself. The synthetic lube is very tacky and definitely added drag to the spindle compared to the lithium grease that I was using. Since my speed is pretty rock solid, I guess the drag is not too high.
Unfortunately bringing the motor closer to the platter also brings it closer to the cartridge as well.

It also results in less contact between the belt and the motor pulley. That seems like a bad idea because there's already so little contact there. Right?
Good point Ketchup. The belt is more likely to slip on the capsan than the platter. Of course if it uses a sub platter that problem is reduced.
I tried it on a "DD" SP10 MK2 and it was off, no way to correct like the MK3 offers speed adjustments so the owner has to send it in.

Not what I wanted to read. I hate this thread.

Seriously: did the built-in strobe of that particular sp10 show that it was holding speed? And the timeline showed differently?
Dev: "I tried it on a "DD" SP10 MK2 and it was off, no way to correct like the MK3 offers speed adjustments so the owner has to send it in."
I believe there are trim-pots inside the chassis that can vary the speed minimally but I just don't know which ones. Maybe the trim-pots are for other functions. I don't have my SP-10mk2 or the manual anymore to verify that. Perhaps other more knowledgeable owners can comment on this. Good luck.

______
Banquo363,

yes unfortuantly. I was told he is sending it to someone to correct which isn't suppose to be too hard. I read from someone else whom posted prior on the old NVS posting in relation to "DD" issues.

Look at this being a positive learning experience and not negtive, no need to be upset.

If your table is off then you can address such, if it is off slightly I would be shocked if you can hear such anyways.

End of the day it's all about listening to music.
I agree with Atmasphere. Turntables with excellent soundstaging (and resolution of fine detail, dynamics and bass detail)are signtaures of TT's with excellent speed control.

In my experience, belt drive TT's with AC moters with ample torque and low friction fair better than DC motor driven TT's all else being equal. I think one way to improve a DC motor driven TT is to increase the mass of the platter with good torque. I suspect that is one reason the Micro Seiki's do well and why the addition of acrylic platters on top of the gunmetal sound better.

Andrew
In my experience, belt drive TT's with AC moters with ample torque and low friction fair better than DC motor driven TT's all else being equal.
Perhaps you should listen to a good DD turntable with a coreless DC servo-controlled motor alongside you Raven AC-2 as I have?
No real comparison actually........
Our dear friend Lew wanted a moratorium on discussions of the merits of turntable drive types but I think that's difficult when it comes to the subject of speed consistency and accuracy?
We have heard of the supposedly superb accuracy of some belt-drive turntables according to the Timeline but as yet we have seen no real evidence?
Is someone able to upload a clip of one of these belt-drives with the Timeline....onto YouTube?
Perhaps you Andrew?
Dev,
The Lenco is pretty near infinitely adjustable, as the idler wheel is driven by a tapered shaft that is an extension of the rotor of the motor. So, if the Lenco was off, it simply needed to be adjusted by moving the idler wheel with respect to the variable circumference of the drive shaft. This is how Lenco attains the 3 speeds (33, 45, and 78 rpm). Rather than fiddle with the idler wheel, I made fine adjustments to the speed of my Lenco via my Walker Motor Controller. As to the SP10 MkII, Hiho got it right. Although there is no user accessible speed adjustment, the proper set-up of the outboard power supply WILL result in exact correct platter speed. If the one you tested was not spot-on, then the tt needed some TLC, is all.
Sarcher,
You make a valid point about the fact that if you move the motor pulley close to the platter, the belt will have a smaller area of contact with the drive pulley than when the platter is distant from the pulley. I was merely commenting that both SME and Nottingham recommend proximity of the two. It is not as good a solution as using a capstan, a la the Artemis tt.

As to the question of hum, I am very surprised to read that you have a problem with hum when the motor is close to the platter on whatever turntable. In most cases the motor and its pulley can be placed or is permanently installed at the left rear corner of the plinth such that the cartridge never gets closer than 7 or 8 inches from the motor (half the diameter of an LP plus half the diameter of the label). I don't know of any cartridge that should be THAT sensitive to the EMI or RFI put out by a typical BD motor. The Lenco motor is right under its platter, and I have never ever heard an issue with induced hum. It is said that Grado cartridges are or were unusually hum-sensitive; perhaps you use a Grado. (I have a Grado TLZ and never had a hum problem with it, however.)

And finally, all this chat is still overlooking what I thought was the real issue: speed variation due to stylus drag. None of the above mentioned observations really tell us anything about that. Unless sensitivity to stylus drag is gross, the Timeline may not reveal it. I guess if the speed is "off" with no load, it is unlikely to be stable with a load, but maybe not. One possible benefit of intentional viscous drag or the "eddy current brake" used on the Garrard 301/401 I think would be increased speed stability in the face of stylus drag, a very good way to deal with it.
Lewm,
Have been reading this for awhile and want to ask a question while throwing in another variable.
The SME, I have the SME 10, is set for Sumiko Celebration, which I have, other turntables use other stylus makers or Sumiko for their voicing.
Has any one tried to see if the degree or speed that the turntable is off is neutralized when the stylus is lowered and its drag can be added to the equation? IOW is the difference from perfect speed via the timeline cancelled once the arm/stylus is lowered and music is playing?
Dear Uru, I am not the font of all knowledge on this subject, hardly. But what you suggest does seem logical; the speed of a tt may deliberately be set to slightly fast with no load, so that it then achieves perfect speed with the load of stylus drag. But in principle, I would prefer a motor or drive system that is robust enough to maintain proper speed under all conditions, because the load of stylus drag is varying all the time due to the groove modulations and also in relation to the distance of the stylus tip from the spindle. It would therefore be impossible to know in advance and for all LPs "how fast" is fast enough to result in correct speed in the presence of stylus drag. So, IMO, this is where torque, the compliance of the drive system, the speed corrective capacity of the drive electronics, etc, come into play.
Thanks, Dev. I was just joking, but your post does move me closer to getting a timeline just to satisfy my curiosity.

And when I'm unhappy with the results (I pessimistically predict), I'll wish I had Lewm's skills or at least easy access to someone with similar skills.
Lewm, The Artemis is an interesting design. I have not heard one yet.

I had hum caused by the motor on a VPI Classic and a LP12. The Classic's motor is on the front left. Maybe if the motor was placed in the rear it would have been better. The LP12 had the motor and power supply under the platter. Could be if I had an outboard PS like a Lingo it would solve the hum. I was not using a Grado. I am sure there are TT designs that have the motor close that don't have hum issues. Just a matter of being well designed.

I have a SP10 mk2a now and experience no hum with the same carts. Sorry if all of this is off the topic of this thread.
Sarcher30: "Unfortunately bringing the motor closer to the platter also brings it closer to the cartridge as well. Which on the TT's I have had with that arrangement caused hum on most of my cartrides. There may be some TT's that sheild the motor well enough to pull it off."
Perhaps you can try grounding the motor housing?

_______
Lew, are you saying that you was able to get the Lenco dialed in with the Walker to allow no drift with the Timeline.
Sarcher, What is the evidence that the hum is (or was) due to the motor/cartridge interaction?

Banquo, I have some knowledge but not much skill when it comes to the electronics of either a motor controller (for BD) or a drive system for a DD tt. If I have a problem, I rely upon Bill Thalmann to deal with it, at my expense. But I do have the good fortune to live within 30 min of Bill's shop.
Halcro, I'm not sure I agree with Peter on this one. Our model 208 has the motor quite close to the platter (opposite the tone arm; there are no hum problems even with Grados). However the 208 uses a motor that would easily qualify as a flywheel in its own right. Keep in mind that in a belt drive, cogging is almost a non-issue due to the rotational speed of the motor, and then really only applies to DC motors for the most part.

AC motors are not particularly prone to cogging effects. The best tape drives all have direct-drive capstan motors, usually AC, and they often have rock-solid speed stability that turntables struggle to match.

The Empire that our machine is based on was one of the most speed stable made for quite a long time. Julian Hirsch complained in one of his reviews of it that the speed variation was "buried in the noise" of his instruments, making an exact number difficult to gauge (although Empire did publish specs at the time). Sounds to me like he could have used a Timeline...

I've played with a variety of belts on the machine. Interestingly, even mylar variants sound exactly the same. Its my opinion that if the belt alters the sound then there is a problem in the drive system somewhere.

So I don't buy the idea that drag in the bearing results in speed stability at all although it would not surprise me to find that some designers may have created this story for reasons of their own (obviously the 208 flies right in the face of Peter's comments). OTOH I don't doubt that the belt-drive Thorens had some problems! I think that is why the earlier Thorens are the ones people are looking for.
Halcro,

In my statement about AC belt driven TT's vs DC motor driven TT, I was meaning belt driven DC TT's, not a DC driven DD.

I have no experience with DD's yet. If I get a timeline will try to post some results.

Atmasphere,

Which Empire TT are you referring to? AC or DC drive ,belt type?
(quote)Sarcher, What is the evidence that the hum is (or was) due to the motor/cartridge interaction? (/quote)

The hum occured when the tonearm was swung over the platter in both cases. With the motor off on the Classic there was no hum with the tonearm over the table. The LP12 was likely the power supply because I had to unplug it to make the hum go away with the arm over the platter. I have solved the hum issue on the Classic by using an outboard Teres motor.
Hiho, The motor was grounded. I am not the only one with a hum problem on their Classic. There is a thread about it on this forum.
And finally, all this chat is still overlooking what I thought was the real issue: speed variation due to stylus drag. None of the above mentioned observations really tell us anything about that. Unless sensitivity to stylus drag is gross, the Timeline may not reveal it.
Lew.......have you not tested the Timeline with and without 'stylus drag' yourself?
I assume all the comments on the Timeline tests are 'with' the stylus playing as demonstrated with 1,2,&3 styli engaged on my YouTube video?
I can assure you that the Timeline is the ONLY device currently available......capable of graphically demonstrating the most marginal of drifts due to stylus drag.
Henry, I've done it both ways with the Lenco and Mk3. The DP80 has no cartridge mounted at the moment, so could not do it with "stylus drag" factor. Likewise, I don't have 3 tonearms on any one tt, so could not repeat that show either.

If the tt is not slowing due to stylus, based on Timeline, then one would also not expect to see it with the KAB, so I am in no position to argue your point that only the Timeline can reveal it. Nor do I doubt you, absent any experience of my own.
I decided to try another method for the thread drive.
I connected a thread to the platter and one motor (green French silk).....whilst another thread altogether connecting the other motor to the platter (black French silk).
2 THREADS
Re-calibrated the motor-controller using the Timeline (needed to increase the speed due to stylus drag) and listened to the previously warbling flute on the Massenet Le Cid.
No warbling now :-)......and the Timeline is slightly more constant than with the rubber belt.
GREEN BELT
BLACK BELT
Halcro - looks like the 2 threads are touching. If so you might want to put a shim under one of the motors to lift it slightly and separate the threads. Would be interesting to try 1 motor/thread. Cheers.
Dover,
I kind of like the idea of not placing lateral loads on the platter bearing....and this arrangement is working so well I don't know what there is to gain with the one motor?
What harm do you think there is if the two threads touch?
Which Empire TT are you referring to? AC or DC drive ,belt type?

The Empire is of course AC synchronous drive. But most of my experience with it is actually with our variant of the machine, which we have been doing since the mid-90s:

http://www.atma-sphere.com/Products/#Atma-208
What harm do you think there is if the two threads touch?

Increased friction and additional vibration/noise, especially when the knot of one rubs past the other thread.
Hi Dev - just curious regarding the sp10 mkII that you tested. You said

"I tried it on a "DD" SP10 MK2 and it was off"

What was the strobe doing while you tested it? I have a seen a strobe on a SP10MkII one time "waver" back and forth - it could also be heard in the music. It needed adjustment. How steady was the strobe light in this case.

Cheers
Dear Mab, L07D is not in service at this time. I am re-wiring the tonearm.
Hi Ct0517,

I really did not pay attention, the owner said it showed dead on and that's what I was going by and when the TimeLine was placed on showed ii was off. The spindle of his table is approx 20 from the wall.

Hi Lewm,

thanks for that info. in relation to the Lenco, don't you think it's strange that a well known source who is selling these replied by saying they are close and not as you did saying it can be set to be spot on? Personally I thought this to be odd, I was inquiring about purchasing from them to have another table and one of my questions. I asked are you familiar with the Sutherland TimeLine and if I were to use mine on your table would it show to be spot on for accuracy playing a record at both speaads?