Speed Stability

We are well beyond eccentric platters here. The experiment is based upon matching the noticeable to unnoticeable eccentricity of the source (the record) to the wow and flutter and surely the unmeasurable runout of the turntable platter. The theory is that a record should sound better at the optimum position relative to the platter. Has anyone ever noticed that sometimes a record sounds really good and at other times just so so? Could it be related to the record's random placement on the platter?

Very true. Eccentric rotation alternately accelerates and decelerates the velocity of the groove past the stylus. Varying groove velocities necessarily cause pitch variations, think Doppler effect. These variations may or may not be audible depending on their severity, the qualities of the whole system and the acuity of the listener.

Rotational eccentricity also alters the balance of lateral pressures between stylus and the two groovewalls. This will affect channel balance and crosstalk and may impair clean tracking.

If a TT has an eccentric spindle or platter, the solution clearly is to repair or replace that table. Mounting LP's off-center just to fix an eccentric table would be the worst sort of band-aiding. (Sorry if I misunderstood, but that's what I thought you suggested.)

OTOH, if you're asking about off-center record holes as the cause of speed variations, Nakamichi used to make a table with an eccentric/adjustable spindle to compensate for this. Pretty complex, pretty expensive, no longer available new. I never used one and don't know of any other tables which address this.

Simpler just to ream out the record's center hole and clamp it in place at the appropriate rotational position to get it centered.

Then it would stand to reason that the position of the record relative to the platter can affect playback quality. What I mean is, if the turntable has a certain rhythm (wow and flutter characteristics) then it must be possible to turn the record relative to the platter, ie say in 10-15 degree increments and effectively match, or optimize the record's eccentric hole tolerances to your turntable and find the best playback position. Sounds like an interesting experiment. Has anyone tried this?

Jeff L,
We didn't take any photos. You might find them online somewhere. Remember I was talking about RMAF 2008, not 2009.

Tony,
Further to what Mosin said, speed variations occur over every possible time span, from the length of an entire LP side to a nano-second or less. A strobe will usefully measure variation that occur over longer times, but becomes less useful (and eventually useless) in measuring variations of shorter duration.

The particular time-domain errors we listened for (and did not hear) on Mosin's Saskia table at RMAF are far too short-lived to be evidenced by any strobe device I've seen. A signal analyzer would reveal them but a strobe's resolution is far too coarse.

More fat to chew...

I noticed while playing records over the past week that the European and Asian pressings seem to be punched true-ie. no visible swaying of my tonearm. US pressings however, seem to be a mixed bag. Some records are true and some I see the tonearm swaying quite a bit. Still, with the exception of the pure test tone section of my test record, I cannot hear the runout in the music.

Nakamichi built a couple of very complex turntables (TX-1000 and Dragon} back in the early 80's that centered the record to correct for off-center spindle holes.

I want to think that some labels did a better job of centering the hole in albums than others. I am almost curious enough (but not quite) to measure the hole position of a group of records to see just how far off they are and how much they vary. Maybe someone has already done that- perhaps even by label so we could all know which ones are better for critical listening.

Tony,

I believe what you may be missing is the sad fact that it may be impossible to fix everything, but all the little things add up, so we try to fix what we can. Look at a turntable the same way you look at an entire system. It will never be perfect, but nothing is left to chance that can be corrected with what is available to its builder.

If one thing is left wrong about a system, or a turntable, in a glaring way, the entire exercise is moot. Suppose someone built an absolutely perfect turntable, but it ran at only 23RPM. That would be obviously wrong. But, suppose someone built a turntable that ran one-tenth of one percent wrong. Would that be acceptable? Maybe, but would it be better, if the guy fixed the tenth of one percent error? Of course, it would. The question is how much can be left wrong, and to what degree.

Now, consider what happens when one thing is fixed that somehow manages to upset some other parameter, and you have the puzzle that turntable designers try to solve. It isn't easy, so they work within the constraints of what they know and can discover. They build with what they can manage to master, and with the help of their smartest friends.

At the end of the day, the hope is that their vision is realized, and that someone out there shares that vision.

Speed stability is one step along that unending path. There are plenty of others, yet to be mastered.

.

After reading these posts the last few days, it got me curious to see how stable my Sota turntable speed is based on listening tests and using the strobe disc. I have a stereo test record so I put that on the platter and then my Sota strobe disk which I clamped down onto the record. I have a 4 inch plug-in fluorescent light that makes a good source for the strobe disc. First, I started the turntable with the tonearm up. I locked in on one rectangle on the strobe disc and noted that it stayed in place for several record rotations. Rock steady stable. Next, I cued the tonearm on the outside lead-in groove of my test record and then locked onto a rectangle again on my strobe disc. As the tonearm dropped onto the record I saw no drift of the strobe disc rectangle. Still rock solid steady. I then played the pure test tones on my test record, 440Hz, 1000Hz and 3150Hz- specifically for flutter measurements. To me and my son, these tones were all steady in pitch. But what we both heard was a periodic shift in the image from center to slightly right. So I go to the turntable and get down eye level with the tonearm and I see the tonearm swaying from left to right. Conclusion: My test record has runout. The hole is slightly off center. I see this same issue on several of my records. So my question is: If the source material has some amount of runout, at what point does spending kilo-dollars for better speed stability yield little to no results? Based on my observations and measurements of my Sota here, what am I missing/overlooking?

Doug,
are you able to post any photos of these rooms?
Jeff L

The 180 gram reissue of Who's Next is slow. Mike

Andrew,

Here's a link to that LP (don't know anything about this seller, just an an example).

One of our nicer sets is a massive Erato box containing all of Vivaldi's opus-numbered sonatas and concertos, from I-XII, with I Solisti Veneti/Claudio Scimone. That's 30 sonatas and 86 concerti if anyone's counting. 20 of the 24 LP's are superb. Four were recorded in a different venue by a different engineer who screwed up the miking, but it's still a great set. Vivaldi by Venetians!

Another good test of TT speed stability is the depth and length of soundfield decays. Most Erato recordings of I Solisti Veneti were made in cathedrals or other large venues, with massive soundstages and near-endless decay periods. This very low level info is easily muddied or smothered by many system errors, including TT speed instabilities.

Apologies to Darren for wandering around your thread. Hope some of this is useful.

KAB speed strobe + SDS = excellent speed stability in my system (TNT).

Thanks Doug,

Yes I remember that lesson! We won't go there :)

I think you bring some valuable information based on your observations since your listening was primarily focused on trying to assess the capability in "timing" of the music which is mainly driven by the speed stability of a TT. Often times people are eluding to this. But it is good to see you focused on this.

I'm a Vivaldi fan and have quite a few records. I wonder if I have the one you're referring to. Can you provide info?

FYI, my latest projects are: waiting for the Mint LP, designing and building a very inexpensive spring-on-mass isolation platform using compression springs and granite, trying the Ortofon MC A90, then going back and comparing the Triplanar and Graham with both cartridges after the set up is at it's optimum. Will keep you informed.

Andrew

Macd, the SDS was a great upgrade when I had the VPI table. It truly allows you to lock in the speed and forget it. Getting the speed right gets the pitch and pace of the music correct. Having said that, I did check the speed every month or so because belts do stretch and change a little but I never had to adjust too much. The SDS also is an AC filter so it probably helped to lower the noise floor. I recently purchased the Continuum Criterion and I can honestly say I have never heard better speed stability and rock solid soundstaging from any other turntable I've listened to except the Caliburn, Continuum's top model. It must be heard; built like a tank and the sound amazing.

Thanks Doug.

Your report and descriptions are clear, concise and invaluable for those of us who aren't fortunate enough to have attended.

Regards
Henry

Hi Andrew,

That cartridge was in the unnamed third room, which I won't identify here. We learned that lesson! (It wasn't a Tranny of course. Your Orpheus would shame it, though the other cart costs far more.)

I can't compare the Saskia and TW AC directly, since nothing about the two systems was very similar. All I can tell you is what the better one *didn't* do.

The Saskia maintained an unflappable rhythmic rightness and drive. It refused to distort any kind of time domain information, whether macro-dynamic big bass and drums or held notes over the fastest mandolin plucks or even the nano-dynamic textures from bow, resin and string (all from that Vivaldi LP). I expected it to handle the big stuff well. I was happily surprised that it seemed to handle the fine stuff just as well. I'd have to hear it with a faster, more resolving arm, cartridge and tweeter to be certain, but its speed errors might fall below my own threshold of detectability. (I don't think anything falls below Paul's, when he's on he's scary.)

The sound in the TW AC room was a tiny bit softer, but never "wrong". Paul gave it his overall best room in show. We didn't necessarily attribute that hint of softness to the table. There were too many variables. We were frankly surprised that a table with an elastic looking belt performed so well. I believe TW's belt material is proprietary, as it should be based on what we heard.

So, all I can say is that there was probably LESS artificial softening of rise times and transients from the Saskia than from any table I've heard.

Our own table (now more carefully tweaked and notably better what you heard during your visit) does pretty well. It has to, since when it's wrong it drives us batty. I'd have to hear two tables in the same system to make actual comparisons though. Tough to do with these 80+ lb. beasts.

Hello Doug,

Interesting feedback. Was the misbehaving cartridge in the Highwater/TW setup or the thrid room you eluded to. Any comments on the gear in room-3?

Also, can you expand on the differences between Saskia and TW AC on this record from a speed stabiity standpoint. while there are many diffeences between the tables, it would be interesting to get your perspective between these implementations of idler and belt drive from a speed styability standpoint.

Cheers

Andrew

I'll support Frogman's general assertion, both from theory and from my own listening experiences and Paul's.

All turntables exhibit speed instability. There are no exceptions, only differences in degree and kind. When a mechanical drive system is confronted with a variable load (ie, stylus drag) at an unpredictable mix of frequencies, rise times and amplitudes, instabilities in platter speed are inevitable. The instabilities can be mitigated by good engineering of many kinds, but they cannot be eliminated. We can use Newton, we can't repeal him.

Can any particular listener hear the speed instabilities of any particular table? Who knows? FWIW, like Frogman, Paul and I have heard few TT's that don't shout certain speed instabilities to our ears.

We aren't musicians, but the music we enjoy is pitch accurate and rhythmically precise, so very revealing of speed instabilities. DSOTM won't tell you much unless the table really sucks. If you want to diagnose a table's speed stability, listen to Mozart or Bach on authentic style instruments, as in the recordings by Hogwood or Harnoncourt for example. Held notes and complex passages in music and recordings of great clarity will reveal TT weaknesses that are masked in heavily amplified and mixed music.

At RMAF 2008 Paul correctly identified 10-15 rubber belt drives without knowing anything about the tables, without even seeing them, just from the sound as we walked in the door. On 2-3 occasions he and I actually said "rubber belt" BEFORE we walked in the door, the time smearing was that obvious.

We brought just one LP to RMAF, an original instruments rendition of certain Vivaldi concerti. I chose it specifically because it reveals two things: speed instabilities of a subtle kind and fundamental/harmonic imbalances. I wanted to hear how Mosin's Saskia table handled subtle speed challenges (I knew it would handle the big ones). Paul wanted to hear if a certain cartridge would mis-handle fundamental/harmonic structures in the way he had predicted (he gets that way!).

We only bothered to play that LP in three rooms, Mosin's, Highwater Sound #2 and the room with that cartridge of interest to Paul. The Saskia handled this LP exceptionally well. The TW Acustic Raven 3 in Highwater #2 was also very listenable. (OTOH, the cartridge mis-performed exactly as Paul had predicted, though worse than even he expected.) We didn't bother to play this LP in other rooms, since we were there to enjoy ourselves. ;-)

FWIW, digital also has speed stability challenges, which we refer to as "jitter". Jitter doesn't sound like the speed instabilities from a TT or tape deck and we don't hear them as time domain issues. They are, but on a shorter time scale and with non-analog consequences.

Lewm, I knew fully well that my comment would raise some eyebrows; I stand by them.

Having said that, I will gladly answer your questions. I am speaking about, as you put it, "constancy", not accuracy. I think the term "stability" is self-explanatory. I have listened to many tables over the thirty five years or so that I have been buying records. Those that I have fairly extensive experience with (althought not in my system, with the exception of the Linn), that I think could reasonably be included in the category of "the best" include: Goldmund Reference and Studio, Rockport Sirius, fully tweaked-out Linn, Technics SP10 MK2, SME, and Forsell. For the record, my favorite of those were the Goldmund Studio, and the Forsell. Of course, the other equipment in use at the time played a major role in the end result. I am tempted to include my own TNT6/ET2 set-up in that group, but although it is very good, I am not convinced, yet, that I can live with it for the long term.

I have already explained that I am very sensitive to speed stability. Perhaps the fact that I play music for a living has something to do with it. And I can tell you that in my experience, all the turntables that I have ever heard demonstrate some degree of speed instability, as compared to the sound of live music. Digital, to my ears, does not. It generally has a rock solid speed stability that is reminescent of the real thing. Now, we can talk about digital sound's failing in that it can sound too tight, and tense, compared to the real thing; but that's another story. I have always felt that part of analog's appeal is that it tends to sound more relaxed; even when it has good "PRAT". I believe that part of the relaxed feeling that it imparts is a result of the imperfect reproduction of rhythm.

I made it clear that I believe that turntables can sound excellent; obviously. But in the area of speed stability, although some can be very very good, there is still some deviation from the truth. In every other sound parameter, mainly as concerns timbre and dimensionality, analog is king, in my experience. Music's most important component is rhythm. Speed stability affects the reproduction of rhythm. To me, it is entirely within reason that changes in "constancy" on the order of hundreds of one percent, are audible. Hyperbole? Maybe. But I trust my ears, and this is what they tell me.

Frogman, You wrote, "No, the speed stability of turntables (even the best), does not equal that of digital sources playing digital recordings." What turntables have you actually auditioned for this property that you would characterize as "the best"? I don't mean to be provocative, but all of us occasionally make hyperbolic statements. Also, when you speak here of "speed stability" are you referring to accuracy (i.e., fidelity to the 33.33 rpm standard) or to constancy (i.e., ability to maintain the exact same speed over short time intervals while listening to music as judged by pitch constancy)? I think you would find that the best direct-drive and idler-drive turntables do very well on both counts, so well that you would no longer even think of the digital analogy. I think the finest belt-drive tables aided by a good motor controller would also cause you to re-think your statement, but I myself have not heard any of those for any length of time in my own system.

Hi had the same problem, but on my NAD 533 TT. I initially though it was the belt. It however turned out that the motor spindle/pulley, on which the belt rests, had got spoilt (the brushes inside the spindle became defective). The belt was therefore slipping, causing a variation in speed and therefore the pitch.

I don't know if the VPI has a similar system (of a belt being driven by a spindle which in turn drives the platter) as the NAD

The rim drive may have speed problems if not set up correctly...there are fixes for all of it. Check the screw tension on the motor pulley(s). Talc or replace the belt(s)

Macd,

I have spent the last couple of weeks dialing in and tweaking my new VPI TNT6/SDS/ET2 setup. I have owned VPI's (HW19's) for many years, and speed stability has always been an issuue to some degree. I am not prepared, yet, to blame VPI's for this, as I suspect that most turntables are guilty of some degree of speed instability. We are all sensitive to particular aspects of reproduced sound. I am particularly sensitive to speed stability. It was, in fact, my unhappiness with the speed instability of my first turntable many years ago, that started me on the road of audiophilia. Here are some things that come to mind:

-No, the speed stability of turntables (even the best), does not equal that of digital sources playing digital recordings. That is what my ears have always, reluctantly, told me. That is the one area, where, for me, digital has it all over analog. It may be acceptable, or even very good, but depending on how sensitive you are to this parameter, it is there to hear.

-Be careful with belt tension on VPI's. Don't assume that more tension is better. May be better for start-up speed, but not necessarily for speed stabiltiy. In fact, I have found that on my TNT, less is better. There is a "sweet spot", where the belt has enough tension to maintain good speed, but not so much tension that the belt wants to creep up or down the platter, and add to the problem.

-Make sure your table is ABSOLUTELY level. If possible check the pulley on the motor (or flywheel) and make sure that it is level. And make sure that it is CLEAN.

-The SDS helped a great deal. Best upgrade, that I have made to a VPI, ever.

I look forward to other experiences from VPI owners.

The SDS will make your motor run a bit smoother and more quietly. It will also permit you to set the speed very precisely and stably. I found with a similar product, the Walker Audio Precision Motor Controller, that these effects also resulted in a remarkable "opening up" of the midrange, where I could much more easily separate instrumental and vocal lines. I think either device or an analogous one made by the tt manufacturer specifically for his motor is indispensible if you are running a belt-drive turntable. But as the others have said, the symptom you describe is most likely due to an off-center spindle hole. If it happened on every LP, and if you could actually SEE a speed variation using the KAB strobe or similar, I would suggest you have a defective motor or you need to replace your tt belt or tighten it.

Hey guys

First I will say that I have an upgraded heavy weight screw clamp so I know its not that. I thought it was my belt for a bit so I boiled it and it shrank back down but did not help the problem.

What is interesting is the comment you two made about an off center pressing. The ballads lp is the most off center pressing in my collection and a bit warped to boot. (like a week old go figure). Anyways for some reason it never crossed my mind that it was the arm tracking horizontal that was making the wow.

Hifimaniac - How much increase in performance can one achieve with the SDS? Can upgrading the motor to a 300 rpm also result in better speed stability?

Thank you guys for clearing this issue up.

I second the KAB...but I don't think your issue is speed. Speed will change the pitch but that would be uniform throughout the record. If the record is "slipping", as in the drag of the needle is pulling the record at times, then a fluctuation in pitch will occur. My guess is that your record clamp needs to be tighter or the cartridge is tracking with too much force (most likely the 1st issue).

Spindle hole being off center would contribute...I agree with above...look at record for warp as well. Speed is very important for constant pitch...but not fluctuating pitches.

Is perhaps the spindle hole slightly off center on the Ballads LP? That would generate the wow you're hearing and explain why your DSOM copy sounds OK.

Get a KAB speed strobe to dial in the speed. Do you use the SDS power with your VPI? This is a great upgrade if you don't and you won't have to check your speed to often.