A Few Turntable Measurements using the RPM Android App

@rauliruegas I apologize.

Also the limits of the ear in the time domain (Fourier theory). 

@kevemaher 

I refer you to a talk by Richard Krebs, and the considerations that went into his latest turntable design.

If you want to hear about higher order moments and their importance, though not in formal statistical terms, and the sampling frequencies required, please do take a look.

 

https://www.youtube.com/watch?v=smib6OJm-T8&t=2065s

@kevemaher  : I never posted that that Technics was a high-end TT so don't put " words " in my mouth.

 

The next links are only for our friends in this thread could in what scenario I recomended that Technics that is traveling to your place:

 

https://forum.audiogon.com/discussions/zyx-house-sound/post?postid=2566659#2566659

 

https://forum.audiogon.com/discussions/zyx-house-sound/post?postid=2567061#2567061

 

https://forum.audiogon.com/discussions/zyx-house-sound/post?postid=2567138#2567138

 

Btw, you are welcome.

 

R.

@rauliruegas I appreciate your willingness to continue this discussion.

However, I have learned much more than I needed from this conversation. I don't regret any of the comments made on this forum. For me however, the need for exchange of ideas has passed.

And I have have acted upon what I've learned.

A Technics SL-1200G Silver is on its way to me. I will have it this weekend.

This will be another learning experience for me.

This purchase is a direct result of your recommendation for "high end" turntables. I thank you for that great tip.

 

 

Dear @kevemaher  : " I was shocked by the poorer performance of the WOW. Acoustic Signature does not publish specs for speed stability, wow, flutter and rumble. "

"" It is very obvious now why Acoustic Signature does not publish these specifications. It could be very difficult to explain why a 70s "entry level" table beats their Double X for wow, flutter and rumble. ""

 

" " I was fooled. I bought it. One of my biggest audio gear mistakes. Won't happen again."

 

You posted about specs and what you measured and even that all " against " results to your AS TT you posted something that speaks fine for the listening quality playback of that TT:

 

""""" I also have a modern table, an Acoustic Signature WOW XXL. The table works fine, although there is no means to adjust the rotation speed.  """"""

 

and when you posted was only ignorance from your self due that that TT you can fine tune the rotation speed.  So seems that that TT is fine TT as you posted. The other issue with was that you don't like its tonearm and you changed but even you don't use your Denon because you don't like the look of the Denon unit  !  !

 

 

""I am also boggled to read that the reviewer summarized that the Double X performance as "high end". ""

 

Well for the reviewer that unit is " high end " but the issue could be something that only you can answer: what is high end for you?   your main reference on your system TTs units and what hipotethically I can think is that maybe your true entry level MS DD-40 is that high end for you:  is it?  and if it is nothing wrong with that. Your answer appreciated.

 

 

""""" I have difficulty accepting commonly asserted "facts" unless there is data that has been peer reviewed. """""

 

Well in this and almost other internet audio forums for sure you will have very hard " times " .

 

My take in audio is that must be an equilibrium between objectivity and subjectivity, both extremes are not something good but the other way around.

 

R.

@kevemaher  : Obviously that mijos and I knew Atmos is entertainment and the posts were only mijos and I entertaiment/humor and that's all.

 

"" We are at the mercy of recording and mastering techs.  "2

I have to add : " and each one whole playback process.

I own not 3 but all those PHASE FOUR recordings and some ar just ok but nothing more.

 

R.

 

 

@kevemaher  : " Is there any scientific data that indicates how a person with "normal" listening abilities perceives audio distortions? "

 

It's weird that less that two hour after your questions you found out the " answers ". Nothing wrong with that.

Now, that's not what I was talking about or what E.Long in the review posted: due to the vacuum clamping all the members on the listening panel heard the difference in the quality/kind of reproduced sound. Not even Long posted nothing about THD or IMD changes with and with out vacuum but more about good damping or as mijo said underdamped .

Anyway, in any listen sound pick up by human been ears we have to take in count that ears is only one tool in the human been to identify sound because you, me and ever one listen through our whole body: ears, bones muscles, nervous skin terminations, hair and the like. Not easy to to it overall.

 

R.

@rauliruegas @mijostyn 

Dolby is mass entertainment, not traditional music. I may be a :"wonderful" "immersive" experience, but it is not music.

This discussion has veered way off topic. Probably time to cap it off.

Thanks to everyone for contributing. I have learned quite a bit about how real audiophiles think about this great hobby. I'm not one yet. I may get there.

 

@mijostyn  : I can't see any one from México but in reality people like you in USA and Europe: 

 

Music Like Never Before - Dolby Atmos Music - Dolby

Dolby Live at Park MGM - Dolby

Dolby Atmos - Official Site - Dolby

 

So you are wrong " again ".

 

Good that you have what you want.  That's all about. Enough for me im this subject.

 

R.

@rauliruegas 

Dolby Atmos? Come on Raul, that stuff is for Mexicans:-) 

What I am saying Raul is only unamplified acoustic instruments present us with a realistic sound field. Everything else is compromised to one degree or another. A great home system is more capable of presenting a realistic impression than the majority of amplified venues. 

@mijostyn  : Btw, I attend for several years at least one day each week to listen live MUSIC.

  """ Are you saying that you can only achieve a satisfactory level of performance at a live performance and that this is not achievable with a residential system?  """

 

Obviously is not achievable in any room/system. Period.

 

Like you I like too the home system " illusion " ( fake ) that is central part of the home stereo reproduction but I'm not so anal about like you.

I wonder why you have not Dolby Atmos?

 

R.

@mijostyn I agree.Electronically shaped and amplified music at concerts is highly processed. It can sound really good or horrible depending on how it is set up. A home system should be able to beat an electronically amplified live concert easily.

Acoustic music, such as that created by a symphony orchestra, piano or organ in a large hall presents music in its natural form. It is difficult to reproduce this sound at home. Resonance induced colorations in a room at home are in the audio band. The resonances in a concert hall because of its size are mostly below audibility, but echo can be heard The concert hall is designed to damp reverberations. There may be poor sounding concert halls, but these are usually quickly corrected.

Music from home systems is highly processed also. We are at the mercy of recording and mastering techs. However, there are a small number of recordings that come very close to the concert hall sound. Solo piano and piano concerto recordings such as "Liszt - Piano Concertos No 1 and 2 Davis Decca VIV 11 (PHASE FOUR )" are my standards. I've found Arthur Salvatore's website, "High-End Audio" to be very helpful for choosing natural sounding LPs.

 

@rauliruegas , Only in instances of unamplified acoustic instruments are you going to perceive a real image at a concert. Many larger concerts have no image at all, they are mono. This does not mean that a stereo system can not create the illusion of real instruments before you. 

@kevemaher 

Trying to do anything over the internet is folly at best. There are way to many uncontrolled variables.

Most of what people say they hear is imagined which is why rigidly controlled studies with a cooperative panel are necessary to say anything.

All audio is personal. We all expect something out of our systems. I want to feel as if I am at a live venue. Needless to say I have never gotten exactly what I expect, close maybe, but not good enough which is why I am still at it. I am a lot closer than I was 25 years ago. This has nothing to do with the enjoyment of music. Most of my listening is done on an inferior workshop system. This is only about the potential performance achievable with todays tech at a less than ridiculous price,

@rauliruegas 

We seem to be like ships passing in the night. Are you saying that you can only achieve a satisfactory level of performance at a live performance and that this is not achievable with a residential system?  I attend a live performance about every other month. The last was Nickle Creek at the State Theater in Portland Maine about one month ago and it was killer. Chris Thile is a major talent. Their recordings are also stellar. Putting them in the media room is easy. Black Midi, not so much. 

All I care about is feeling like I am at a live venue. Many recordings make this impossible but that does not mean that I can not appreciate the voices of Billy Holiday or Enrico Caruso. With many recordings it is. System (includes the room) errors like sibilance and exaggerated high frequencies destroy any possibility.  Amplitude errors are far more pervasive then either IM or Harmonic distortion. What seems to bother me most with turntables is problems that interfere with pitch, more wow than flutter, things like offset spindle holes and warped records.  

@rauliruegas  I would like to understand what type of studies have been made before I make the effort to design and perform the tests needed.

Since my last post I have been searching. I have found one (links below) that seems to be quite thorough and rigorous.

 

https://archimago.blogspot.com/2020/01/internet-blind-test-is-high-harmonic.html

http://archimago.blogspot.com/2020/06/blind-test-results-part-ii-is-high.html

http://archimago.blogspot.com/2020/05/blind-test-results-part-i-is-high.html

 

It may not answer all questions on this subject, but does provide some thought provoking results.

Dear @kevemaher  : Obviously that you are not bashing anyone but instead of all those questions where you already have the answers then why not really enhance or apport something where all of us could be beneficiated for example: that you take your knowledge levels and make a mathematic model with measurements with the explanations of : what to measure, where to measure, how to measure and what all those makes sense to you and to any one of us.

Scientifics along neurologists already made some research with measures how the brain and which brain parts react to some sounds and not specific on sounds of the ones in our audio hobby. In the mid-time you can google for those studies that even in Agon ( somewhere )  were posted and again with no relationship with the audio hobby.

 

You can start with your self at the end you are an audio hobbyst.

R.

 

R.

 

R.

@mijostyn  : I don't know where you want to arrive. The power is just intrinsical in a live MUSIC event ( no one is preaching there and certainly not the Orchestra Director. ) and I thiink that any one but you already understood what I posted and the links I posted.

For your " 20 + " latest posts in the thread you are living inside that imagin that according with what you already posted in the threads is a main characteristic for any room/system

I don't know know if you attend to live events to enjoy the imagin. Not me. Anyway please tell me what can you appreciate in a single horn player at live SPL if you are seated nearfield say 2m.?. Maybe you know something that I just missed or we are talking of different " things ".

 

R.

Is there any scientific data that indicates how a person with "normal" listening abilities perceives audio distortions? What are the lower limits or perception? Is there an emotional reaction to different frequencies?

The commonly accepted sating that "even order sounds "good" and odd order sounds bad" is ubiquitous. Is there scientific data to back that saying up?

If there are studies of this perception, I would really like to read references to that data.

I have difficulty accepting commonly asserted "facts" unless there is data that has been peer reviewed.

Pleas note that I am not bashing anyone. I am looking for explanations that are based on studies not commonly accepted sayings.

@rauliruegas 

I think your preaching to the choir. 

Perhaps a better way of putting it would be transient power. It is not just enough to be fast but a system must be powerfully fast. This is one of the characteristics of sound quality. Imaging exists as its own category with a different set of determinants. A system can have the right balance of frequency ( amplitude response) and be powerfully fast but still not image well. A system can image beautifully yet lack realistic transient power and not have the right balancer of frequencies. A great system will line up all these factors, have lifelike transient power, the right balance of frequencies and image correctly. Any variation from the ideal are what Raul characterises as distortions (of reality)

@mijostyn  : This was what I posted a few months ago in other thread and was not the first time on that issue:

 

https://forum.audiogon.com/discussions/top-two-most-important-sound-qualities/post?postid=2560319#2560319

 

https://forum.audiogon.com/discussions/top-two-most-important-sound-qualities/post?postid=2560702#2560702

 

and this related in other " diferent " thread:

https://forum.audiogon.com/discussions/how-can-you-evaluate-a-system-with-highly-processed-music/post?postid=2561802#2561802

 

Today on those issues is my overall " take ".

 

R.

Dear @terry9 : MUSIC and MUSIC in a home and its reproduction quality levels belongs to Transient Response. That first MUSIC note and notes attack is what ,for me and my MUSIC life, I think is what defines the step by step MUSIC score we are listen. That transient response obviously develops harmonics.

In a room/system where nothing is perfect: where are developed everykind , not only distortions/colorations, of poor transient response according with each system link where something is poor too in some frequency ranges.

Your first hand experiences as me and the listening panel in that TT review along the reviewer tell us ( you and me ) exactly the importance of those transient response and what we " losted " through that dull reproduction were only bad distortions right at the " edge " and that now just dissapeared.

My last " dull " experience in my system was in the early last year when I decided to change the attenuators/volume in my phonolinepreamp. Years ago I bought those new attenuators that came with the same Swiss mechanism that the ones I used to, difference with the " new " ones is Only that the old ones where builded with true hole resistors and the " new " with SMD resistors.

I made the change and was truly dramatic and the first impresion was sad for say the least, yes Dull sound but after a few hours I took again that what I losted were those distortions that normally gives that " over bright " sound. Now those transients are marvelous and obviously puts me nearer to the recording because the brightness is more natural near the live MUSIC brightness.

Yes, we are accustom to that wrong brightness. My audio system is full on SS electronics with ( for me ) high resolution .

Over brightness lives in many of the audio system links of that system chain. Through the years our ears goes down in its sensitivity and that over brightness is " welcomed " and normally is not our fault till we have that " dull " experiences and then we learn about and take action in that audio room/system. In the other side for several audiophiles that true overbrightness they take as: clarity, transparency and the like when in true are only added distortions what gives that kind of " clarity " and that can happens at both frequency extremes not only in HF.

 

R.

 

I think that both of you make good points.

For 40 years digital has claimed perfection, while getting better every year. It is still too bright for my ears, but an entire generation has been brought up to think that brighter is better. I have noticed that every major improvement to my system, US cleaning, reflex record clamp, Koetsu, air bearings, every one removed copious amounts of high frequency, yet after a few hours, it was obvious that the sound was closer to the concert hall.

So I concluded that what I was after was ’smooth’.

Raul talks about there being bright in a bad way and bright in a good way, which I also think is quite right. Mijostyn talks about this too.

Might both of you be referring to the leading and trailing edges of the signal? Electronically, this performance is dictated by odd-number harmonics (square wave Fourier Series). Unfortunately, distortion of the odd harmonics is notorious for being offensively bright.

I think that you are both onto something.

 

Dear @mijostyn  : " The comments about the turntable sounding "dull" only for everyone to decide that the reference system was too bright is a characteristic that is legion in high fidelity systems. There is a tendency for us to prefer brighter reproduction, brighter is better.

  "I don't think that " brigther is better, as a fact the live MUSIC has that " brihtness " characteristic in a Natural way. So there is brighter and " brighter and not always the same word means the same.

That " dull " characteristic you mentioned and the reviewer too came from the listening panel and for those old times the reaction of the member of that panel is just normal because when you listen for the first time a LP with vacuum hold-down  audiophiles think that that vacuum mechanism suck the sound and from there the " dull " kind of sound but E.Long posted that after some time listening ( he not the panel members. ) to the Sota he was convinced that the sound is not really dull but more " realistic " and I remember that when I bougth the  AT666 vacuum stabilizer as an after market item my first impression was exactly that: " dull " and was disappointed with and time latter on I took in count that the sound was nearer to the reality with the room/system I owned in those " times " and that today in many ways is "  different.  ".

 

The sibilance issue is a sound characteristic more on female voice and we even listened in some live events and not necessary associated with poor imaging.

In the other side we unknow all the recording process of each LP where the sibilance could be developed but on the playback process some phono cartridges tend to sibilance more than others. As with low bass many times room treatment can't make it disappears. To many challenges to defeat in a home systems where exist no perfcetion but the other way around.

 

R.

@rauliruegas 

I'm not sure what you mean Raul. Could you restate your last comment?

@rauliruegas 

I read that review back in the day and It's positivity over vacuum clamping remained lodged in my neurons. The comments about the turntable sounding "dull" only for everyone to decide that the reference system was too bright is a characteristic that is legion in high fidelity systems. There is a tendency for us to prefer brighter reproduction, brighter is better. There are many problems that will cause high frequency aberrations. In this review it is the high frequency resonance of underdamped records. But this problem also occurs with digital sources.  It manifests itself as sibilance and poor imaging. Sibilance is obvious but the effect on imaging is more insidious. I "look" for it by listening to cymbals. The entire frequency palate should emanate directly from the cymbal. The cymbal should be in focus. Instead the cymbal will have a glow of high frequency. At its worst you can not define the cymbal at all. It is smeared across the stage. The usual cause of this is poor room control with omnidirectional loudspeakers. With a system that seems to sound dull listen carefully to the cymbals. If the cymbal is sharply defined and all the high frequencies are present and sibilance is totally absent you listening to an accurate system in a well managed room.....with vacuum clamping:-) 

Dear @kevemaher  : Do you want to know what other audiophiles think on turntable different Drive Designs?

Well in at least 2 of the 5+ analog threads this gentleman: @mikelavigne  participated and he owns those 3 today top TT's you ask about. This gentleman builded his home system through many years and I know that first than all he is a MUSIC lover.

Before the TT's he owns today he owned at least other 2 top TT's in those learning years: the Goldmund Reference and latter on the Rockport Sirius 3. I followed his audio history for to many years and here his today system:

 

Mike Lavigne's System | Virtual Listening Room (audiogon.com)

 

R.

Dear @mijostyn  : This is the one for you and  for the OP because this is not DD but BD design:

 

Audio-1986-06.pdf (worldradiohistory.com)  page 98.

 

R.

@kevemaher  : In this forum there are 5-6 threads dedicated to your same question and the issue is not exactly the drive TT design because the kind of drive is only one TT characteristic and yes very important but there are other very important characteristics too like: platter build material or blend materials well damped, well dampend isolated arm board, excellent damped suspension, silent bearing, tec, etc,.

At the end no matters the drive design the TT must be inert with out any kind of " sound " by it self . It has to be speed accurated and with good speed stability. 

I that scnario any of those 3 drive designs can make the job. Design , materials and quality level excecution is more or less the name of the game.

 

Please do a fast search in Agon forum to find out those TT threads.

 

R.

I thought about starting a new thread, but the conversation on this one is a good intro into my next question.

 

"How does one choose between belt drive (including string, fishing line etc...), direct drive and idler drive?"

 

There seems to be two crowds, direct drive vs all the others. I've had both. I had a bad experience with the AS table, but that could be an isolated problem. I really don't have a preference.

Very curious to hear ideas!

@rauliruegas Thanks for the links. Great reading material. Seems like companies use whatever measurement protocol they feel is appropriate. This is very similar to the "alphabet soup" of specs that exist in the Optics and Electronics engineering world.

 

@terry9 Thank you very much! And thank you for joining in. I'm having fun learning how other real users think about audio and audio gear. I can't get that here in this countryside location.

Thanks to everyone else also.

Dear @kevemaher @terry9  and friends  : This is a learning TT reviews for measurements that came from 1985:

 

Audio-1985-02.pdf (worldradiohistory.com)    page 58.

 

and this another one:

 

Audio-1985-04.pdf (worldradiohistory.com)  page 62.

 

R.

 

Dear @kevemaher  :  As you said almost no manufacturer disclose the the whole measurements process they used including the different standards they used.

Here some examples:

 

http://www.thevintageknob.org/technics-SP-10MK3.html

 

http://www.thevintageknob.org/denon-DP-100M.html

On specs this Denon TT is the only that shows Measured spec on speed fluctuations: 0.06%

http://www.thevintageknob.org/micro_seiki-DD-100.html

 

http://www.thevintageknob.org/yamaha-GT-2000.html

 

http://www.thevintageknob.org/sony-TTS-8000.html

 

http://www.thevintageknob.org/sony-TTS-8000.html

 

http://www.thevintageknob.org/garrard-401.html

 

Your AS 60db is prety " decent " for a BD design and is really close to the DD MS unit. Btw, @mijostyn  my vintage AS TTs never showed that rumble you mentioned is reflected in the subs not only that I do not noted by " eyes " but neither with my fingers against the Denon DP 80 and the Technics SP 10MK2.

I think that the OP really puts the " finger " where it hurts when posted:

 

"" How low do wow, flutter, and rumble have to be before they become inaudible in a "typical" listening situation? ""

 

That is in true the real issue for us MUSIC lovers and audiophiles and for what I know I think that no one measured till today with the same standards/process.

 

I remember that in cartridges the separation spec that normally is measured over the frequency range but manufacturers only gives the measure at 1khz and main reason ( I think all we know it. ) is that at both/near frequency ranges the " figure is way lower over the " figure " showed by the manufacturer that today I think no one gives as in the past when the cartridges came with athe measured diagram of frequency response and separation from 20hz to 20khz and with the test record used, at what temperature, VTF and the like and speed velocity of the diagram.

In those " gold " times audiophiles were way better infortmed to decide what to buy and in those times and talking of cartridge separation specs with severaltests and measures was accepted that the minum separation spec must be 20db with no " difference " if that figure goes to 30db because separation is not linear/flat.

Lyra Atlas Lambda SL shows 35db on that spec but Allaerts Formula 1 is 70db at 100hz and 20khz and " only " 60db at 1khz but neither manufacturer disclose the measurement process about.

 

R.

 

 

@mijostyn I use REW for room characterization. It is freeware. The functions appear similar.

Speaking of environmental noise coming through. What about using those rare earth magnets to levitate the turntable.  Maybe use rubber bands to keep it in place.  I just might try it.  Sounds like a fun experiment.  

@kevemaher 

I was never an AS fan. I do not care for units that go out of their way to look flashy without obvious benefit. Having said that there are four sources of noise when playing vinyl, the turntable, the record, the environment and lastly electronic. I assume you used the same record for all measurements. The environment is basically the same for each table and to my knowledge none of them have isolating suspensions. Electric noise would also be the same for each table. The conclusion you came to is correct. The AS has a Rumble issue. Rumble is a problem if you can hear it or if it affects the performance of speakers particularly subwoofers. I also think it is a significant marker of overall quality. It is also possible this turntable was damaged.

I had an 80s era MS turntable which was wonderful. Its only failure was lack of a suspension. The apartment building I lived in had the worst environmental rumble problem I have ever lived in. The AC compressors were clearly audible in spite of concrete floors, all 19 stories. Because of this I returned to the Linn LP12 which was much quieter as long as you tip - toed around it.

Measuring is always the best way to confirm anything. You also discover that “ears” have limited sensitivity when dealing with certain things as it sounds you only identified the problem by measuring.  Measuring is also a great way to train your ears. If you really want to have fun get yourself a Dayton Omnimic V2. They are about $300 and worth every cent. You need a PC. The program is free but you need to have a serial # to access it. In the process you download the calibration file for your microphone. You will find it essential for possitioning loudspeakers, adjusting room treatments and writing target curves if you ever get into digital signal processing.

Thanks for the discussion, @kevemaher .

@kevemaher I agree that wow, flutter, and rumble measurements are quantifiable and repeatable and agreed upon. I think, however, that this is not the whole story and that a 50KHz sampling rate would give us the data needed for a more robust analysis.

@terry9 There is a well-defined method for measuring wow and flutter and rumble, which only differ in frequency and source, but not in nature. This method turns out to be quite complicated. Whether the RPM app developer used this method or not is not disclosed. This makes comparison between published results and the RPM app results dubious. I do think that comparisons between tables using the same app (and phone) are valid qualitatively. That's why I feel sanguine about the comparisons I've made and reported.

If a manufacturer clearly states the method used (there are standards), then it can be used as a valid comparison between this table an others measured using the same method. It happened that I did measure the same wow 2 sigma as the spec sheet for the DP-57L and the DD-40. This may be coincidence. If a manufacturer does not provide a spec based on a standard protocol, then no valid conclusion can be made, obviously.

I find it difficult to believe that a manufacturer would not measure their product according to the well-accepted protocol. Engineering must have used some quantifiable method to characterize their creation. Engineers need a goal to reach. They need a goal that tells them that they've reached the goal and can freeze the design, stop development and move on to the next problem.Sales and marketing can decline to publish the results for a variety of reasons. Whatever the reasons, I feel a bit queasy without reported specs. I made this mistake with the WOW XXL. I will never do it again.

The test only goes to 200Hz. Any software and hardware (computer with A/D if chosen to do digitally) will have plenty of bandwidth (sample rate) to provide accurate results. The actual test uses a different frequency (3kHz or 3.15kHz), This frequency is detected, not speed. This makes the measurement more accurate because integration (averaging) times can be very short.

Implementation of the standardized protocol with all due attention to the accuracy of the test gear can accurately reproduce kHz frequencies. But only the errors that show up below 200Hz will be used to develop the result. If your hypothesis is correct, there is no method known today to capture errors from frequencies higher than 200Hz.The spec would have to change.

I have been in Engineering my entire career developing products for medical research, defense and communication at the highest level. What I've stated above is a part of how the development process works. Specs are designed so that they are measurable. If it is found that a method does not capture all the errors known, then the spec method is changed. Development cannot proceed without a measurable goal. In fact, turntable engineers may have an in-house spec to reach, knowing that meeting the in-house spec will guarantee that the industry standard method will produce the desired performance.

I don't presume to be an expert in measurement methods for characterizing turntables. I'm learning. Meanwhile, I call on my work patterns to inform me how I would proceed if developing a table. Differences in my approach to turntable engineers approaches may differ in details, but are the same in nature.

I do agree that some things are difficult to quantify. Turntable performance is not one of them. Whether one prefers this or that table is an emotional decision, a valid concern.Wow, flutter, and rumble measurements are quantifiable and repeatable (and agreed on).

@kevemaher  

With all due respect, keve, I think that you are putting the cart before the horse. Before one aggregates observations, one must make observations. The difficulty with making speed observations is that for practical purposes they must be averages: distance travelled divided by elapsed time. This is not an instantaneous quantity.

Even aggregating a finite number of observations implies discrete, not continuous. That means sampling frequency.

This is not a moot point because modern controllers tend to correct speed at about 10KHz. If it were easy, they would correct more frequently. I doubt that an app is better; in any case, it's important to quantify the limitations of the observations; in this case the granularity  imposed by sampling frequency.

Then one could aggregate the data into moments, from which the central moments of mean, standard deviation, skewness, kurtosis, etc. could be calculated, although perhaps a spectral or Fourier analysis would be more revealing.

There is no problem with the data arising from a process which is not perfectly random - it is data. The point at which randomness enters the picture is in identifying which inferences are valid, and which are not.

Yes, I think that speed stability is a problem. The question then is, "Which frequency?" I strongly suspect that most of the audible differences between turntables arise from small speed variations in the lower kilohertz range, which we hear as  brilliance or sibilance. It is obvious to suspect speed instability of causing this - but at greater frequencies than are usually measured. For example, bearing noise affecting speed.

By way of evidence, a common criticism of Nottingham turntables (high mass, low torque) is that they are 'dark', that is, without brilliance. I prefer the term 'smooth'. Also, that is how the bearing noise from my 1.8W motor manifests itself. Yes, it's repeatable.

As you point out, "Measuring performance parameters of instruments is crucial to product development." But unfortunately, associating numbers to phenomena is one of the most difficult human activities - doing it right, that is. It is therefore of cardinal importance to report the limitations of the measurement before reporting the results of the analysis. In my opinion.

@rauliruegas Hi, Thanks for the link. Surprisingly, the wow and flutter reported for the Double X by the author of the article you referenced is the same as the wow value I reported above for the AS WOW XXL using the RPM app. This result is encouraging, but not enough for me to trust completely, because the method of analyzing the data may be different.

There is no denying that the Double X measured wow value is 5x higher than the 0.02% I measured for the DP-57L table using the RPM app. Even more damning, the Double X it is worse than the wow reported for the Micro Seiki DD-40, an "entry level"  turntable.

The rumble spectrum is also quite informative. Although I can't make a 1:1 comparison with my (unpublished) results because gain and reference voltages may differ, I can say that the rise in noise from the 500 Hz baseline to the peak at 10Hz is about 60 dB for the Double X table in the article. I'm using the blue curve. This may be an incorrect trace, but there is no legend to indicate what the conditions were for each curve. My results indicate only a 30 dB rise for the DD-40. This is a 30 dB (30X) difference!!! Perhaps the region around the Double X was particularly high in vibration on the day of measurement. Or the line filtering in the Double X power supply is poor design or faulty.

One can also see the on the same chart a 50ish Hz peak.frequency. It rises 60dB above the baseline. The source is not identified, but is probably the AC line frequency. My measurements used a rumble track on the Hi-Fi News test record. The AC peak for the DD-40 is not visible, buried in the noise, which is already lower than the Double X.

It is very obvious now why Acoustic Signature does not publish these specifications. It could be very difficult to explain why a 70s "entry level" table beats their Double X for wow, flutter and rumble.

With all this now under our belt, can one say which table sounds better?

No.

But if one had to pick a table based on these results, the choice is clear.

I am also boggled to read that the reviewer summarized that the Double X performance as "high end".

How low do wow, flutter, and rumble have to be before they become inaudible in a "typical" listening situation? If the value is higher than that of every measurement result shown here, then the better performance of the DD-40 and DP-57L is not really needed. The Double X performance will be indistinguishable from those tables. But I think the answer is that since the manufacturer cannot control the conditions that a buyer will use its product, the manufacturer must strive to equal or beat the performance of the other "high end" tables.

If none of those publish these specs either, then my entire discussion is meaningless, since there's no way to determine from measurements which table is "better". Listening is always a very good method, but is usually highly compromised in any showroom environment. Perhaps listing is the only spec to test for. But how many people purchase a table without extensive listening to it prior to that purchase? I'd wager most do.

Dear @kevemaher  : As you I bougth my units at blind on specs and were ( two units ) coming from an audiophile that I respect, so second hand at very good price: 2 top of the line ( in those times. ) TTs with 3 outboard motors and one motyor controler that I had to modify to choose between one TT or the other and till today I have not a single issue with those AS and the " belts " I use are simple silk thread amnd yes I have to push-start. In reality a critical issue with my model TTs was that came with no kind of damping footers so what I did it is to put 3 AT-616 pneumatic Audio Technica footers and a top these footers goes a centered an inverted aluminum tip-toes that for me makes very good job.

 

Here you can read some real time measurements in one of AS today model:

 

https://www.acoustic-signature.com/files/downloads/tests/2021-08-stereoplay-double-x-neo-ta-500-neo-mcx1-en.pdf

 

R.

@brev Yah, it is fun making these measurements. I wish that the developer would publish his/her methodology. For example, what algorithm is used for the WOW calculation? Is it one of the standards?

I don't think we'll find out any time soon. Apps are usually closely guarded secrets.

But he/she could indicate which standard he/she is following, if any. Without this knowledge, it is impossible to compare RPM results to manufacturers' published performance.But relative performance between tables is valid.

I believe in these RPM apps!  Perhaps that is because my 42 year old direct drive Denon DP-30L measured so well. Spot on RPM and decent wow. Thanks for the tip!

@mijostyn The belt is brand new. Just put it on about a month ago. The old belt had stretched. The measurements I reported using the RPM app were done with the new belt.

 I was shocked by the poorer performance of the WOW. Acoustic Signature does not publish specs for speed stability, wow, flutter and rumble.

Seems that AS relies on the marketing of their special spindle material, the huge platter and the brass inserts to impress buyers. Must be good performance with all those buzz words, right. A simple measurement shows the difficulty of relying on bling rather than real measured performance. I was fooled. I bought it. One of my biggest audio gear mistakes. Won't happen again.

Hmmm terry, 45 kg is ...... like only 99 pounds, not even a hundred.  Watt?  1.8?  

 

Wow.  So on my Music Hall with the I think like a DC synch 4 watt motor I can do a 90 kg platter.   That's a lot of 4 oz fishing weights I have to glue on. I better get going to the bait and tackle store to improve my stereo. 

Replace the belt on the wow and measure again. Let us know what happens.

@terry9 Like with many quantities, the speed aspects of turntable rpm can be described as a mean surrounded by skirts on either side. I say this with trepidation, because the turntable noise is not a stochastic (random) phenomenon. It can have resonances, for example. However, narrowing the width of the frequency spread and diminishing the signal from resonant sources is a worthy goal.

Some say that a turntable that has poor rpm control cannot bring out all the nuance that a high end cartridge can pick up from an LP. This reason alone is why some people are interested in the stability of the RPM. The human ear is not a good instrument to evaluate rpm. One may prefer one or an other method of rpm control because the sound of one is more pleasing than the other. Comparisons based solely on listening is obviously important. This type of comparison is not quantifiable by nature. Specs are there to provide a guide to potential users.

Engineers develop a product based on numerical specifications that the company's sales and marketing generates. Engineers use test instrumentation to measure and compare design approaches. Without a formal methodology and explicit specifications, engineers do not know what nor how to build a product. And importantly, when to stop engineering and consider the problem solved.

Measuring performance parameters of instruments is crucial to product development.

Any company that does not report these values via a spec sheet is denying the customer one way to evaluate and compare different instruments. Some customers need to see these specs because they provide a baseline for the performance of the instrument.

Not publishing a spec prevents that from happening. Often known code words or phrases are used to appeal to the emotions of particular enthusiasts. These are not specs. Perhaps some don't care. I do.