9” vs 12” pick up arms. The mechanics explained minus the anecdotal B.S.

[Loheswaran]

No Chance you have the Dinsdale White paper that inspired the Townshend Rock line

http://swedishat.com/articles.html

Good article.
Like I said in 'the other thread' Max Townshend shares the same opinion on arm length. He explained to me clearly that we are controlling the movement of a tiny needle at the end of an arm - a bit like holding a pen at a distance on a moving table trying to write a letter - the silicone has the effect of steadying/holding the table still.

It would be nice if you had a link to the original Rock 'white paper' explaining the use of the trough.

BY the same token it makes sense to keep the pen closer to you I guess.

 

[microstrip]

My interest in this debate is also indirectly connected to turntable diameter. Using a 12" tonearm would allow me to get a 17" diameter platter having a moment of inertia that is almost the double of that of a typical 12" platter. Theoretically I could have the sound quality of a 20 kg platter with a much more reasonable 10 kg one ... However a 16" diameter platter excludes the possibility of owning any 9" tonearm. Choices, mostly exclusive choices ...

 

[TLi]

Marc Gomez makes a very good point in saying most cantilevers of cartridges are not mounted straight. A small deviation of 1 to 2 degree is not easily detectable with naked eyes. The advantage of a 12" arm over 9" only reduces the angular tracking error in less than 0.5 degree.

 

[Halcro]

http://swedishat.com/articles.html

Well it may be true that Marc Gomez has a Mechanical Engineering Degree and studied materials science....but reading his 'explanations' for the 9" preferred tonearm length.... he seems to lack the necessary Structural Engineering qualifications to complete the picture...?

He includes a diagram titled "Effect of length in vibration amplitude and frequency" and shows a diagram (and speaks of) a cantilevered "ruler" of a short length compared to a longer length.
Now on the face of it, this all seems reasonable and is certainly true of a pure cantilever.....
But a tonearm with the cartridge resting on the record is NOT a pure cantilever.
It is a PROPPED cantilever and all the Bending Moments, Shear Stresses and Deflections are entirely different (and change with the degree of VTF on the stylus) to that of a pure cantilever.
So the SAT arm has been designed by Marc Gomez as a tapered tube (from pivot to cartridge) which mirrors the stresses of a pure cantilever much like other tonearm designers like SME have also done.

Continuum Audio Labs with their Cobra and Copperhead tonearms utilised a team of qualified University Experts with access to advanced software and technology to model the arms using NASTRAN, PATRAN and DYSTRAN finalising in the complex process of Gradient Shape Optimisation using Reshape.


THIS is the true shape of the stresses involved in a 'Propped Cantilever' and the true shape for maximum RIGIDITY for that application.
The SAT tapered tube is NOT the correct shape for maximum rigidity of a propped cantilever whether it's 9" or 12".

Now I'm not denying Michael, that you prefer the SAT on your Caliburn over the Cobra......but I'm pretty sure it's not because the SAT is more rigid than the Cobra.
And if Mark Gomez can make an elementary mistake on physics....his justifications for 9" over 12" are suspect IMO.
If you compare the shape of the Cobra and Copperhead arms to the SAT (and also the Kuzma 4 point and SME)......you will find that a simple 'tube' more closely approximates the shape of the Copperhead than that of the SAT.
And if you look through the history of tonearms and study the slenderness ratios of some of the tube tonearms throughout the decades........the Moechs, the Hadcocks, the long Micro-Seikis and SAECs let alone the Shroeder tonearms... would never pass the first listening test if Marc was correct about his theory of rigidity.

A tonearm only has to be rigid enough for the purpose.
It's like a structural engineer telling a client he can make his floor more rigid if the room were 10 foot wide instead of twenty......
Most tonearms are rigid enough....
There are other reasons you find the SAT arm so superior

 

[ddk]

Marc Gomez makes a very good point in saying most cantilevers of cartridges are not mounted straight. A small deviation of 1 to 2 degree is not easily detectable with naked eyes. The advantage of a 12" arm over 9" only reduces the angular tracking error in less than 0.5 degree.

Poor setup is poor setup that doesn't diminish the advantages of 12" arms. If one's not measuring the cantilever length and stylus position the arm lengths not going to change habits.

david

 

[ddk]

W
A tonearm only has to be rigid enough for the purpose.

Agreed and there's so much more affecting the sound quality than rigidity.

david

 

[TLi]

Poor setup is poor setup that doesn't diminish the advantages of 12" arms. If one's not measuring the cantilever length and stylus position the arm lengths not going to change habits.

david

The point is the benefit of 12" over 9" arm in reducing tracking error/distortion is less than 0.5 degree. In order to enjoy this extra 0.5 degree reduction, the setup tolerance of stylus cantilever on the protractor has to be less than 0.5 degree. Otherwise, it is rather arbitrary and random. It is difficult to know the exact tolerance or accuracy of individual setup, I guess even with best magnifier and setup aids, the variant will be greater than 0.5 degree. If the spread is a few degrees, which is entirely possible, the 0.5 degree gain from 12" is meaningless.

Those who claim 12" sound better will have to give more evidence other than tracking accuracy.

 

[microstrip]

The point is the benefit of 12" over 9" arm in reducing tracking error/distortion is less than 0.5 degree. In order to enjoy this extra 0.5 degree reduction, the setup tolerance of stylus cantilever on the protractor has to be less than 0.5 degree. Otherwise, it is rather arbitrary and random. It is difficult to know the exact tolerance or accuracy of individual setup, I guess even with best magnifier and setup aids, the variant will be greater than 0.5 degree. If the spread is a few degrees, which is entirely possible, the 0.5 degree gain from 12" is meaningless.

Those who claim 12" sound better will have to give more evidence other than tracking accuracy.

The argument can be easily reversed - errors are cumulative and audibility has thresholds. If you already have an initial error, your system becomes much more sensitive to small amounts of error. The distortions in this process are not linear, as explained in several articles.

 

[Narayan]

It was great to read the original source at due time, but IMHO Mark Gomez article adds little to the serious debate, keeping the physics at the almost childish level.

He dismisses the 12 inch tonearm in a single sentence : "The very small reduction in the absolute tracing error associated from going from a 9 inch to a 12 inch arm is marginal compared to the much greater potential for improvement in terms of rigidity and its associated distortions, in a properly designed 9 inch arm."

The argument of some of the 12 inch proponents is just that this distortion is incremental, and that the difference between a 9" and 12" is important, as the threshold of clear audibility is reached with 9" tonearms.

I do not have any horse in this race, but a quick search has shown me that this subject has been studied in many articles along decades, including refereed scientific journals, and is of great complexity and divergence. A simplistic intuitive approach can help to understand the problems, but never to rank their dimension. Just to show how a small detail that can affect our intuitive perception - should we address distortion before or after the RIAA filter? Manufacturers just pick what favors their designs to teach us.

The final judge in this debate is the subjective audition. Mark Gomez is a talented engineer and has designed a great tonearm, appreciated by many. He feels that 9" is his best approach. I am prepared to accept that his 9" should be better than his 12" after reading from him. But also to accept that another designer, using a different approach, can design a 12" tonearm that betters it.

My inner child thanks Marc for letting it read the paper without boring it to death, we´re talking pick up arms here not antimatter or Hadron Colliders. I think you might have also missed this part:

"Disclamer: this is not intended to be a scientific article; I try to keep it strict and accurate without being heavy to read. It does not cover the whole system and interaction between components. Nevertheless, this does not change the outcome!"

 

[microstrip]

My inner child thanks Marc for letting it read the paper without boring it to death, we´re talking pick up arms here not antimatter or Hadron Colliders. I think you might have also missed this part:

"Disclamer: this is not intended to be a scientific article; I try to keep it strict and accurate without being heavy to read. It does not cover the whole system and interaction between components. Nevertheless, this does not change the outcome!"

No, I did not miss it. But my point is that the article is not strict or accurate as others also pointed, and it was used to drive the reader to a marketing conclusion. Please note that this happens with most high-end white papers, not just this one. My main point is that the boring details can really change the outcome!!! We are debating the 9" versus 12" interesting and challenging issue, not the author.

BTW, fortunately we can have many strict and accurate articles about antimatter or Hadron Colliders that are not boring to death.

 

[awsmone]

Well it may be true that Marc Gomez has a Mechanical Engineering Degree and studied materials science....but reading his 'explanations' for the 9" preferred tonearm length.... he seems to lack the necessary Structural Engineering qualifications to complete the picture...?

He includes a diagram titled "Effect of length in vibration amplitude and frequency" and shows a diagram (and speaks of) a cantilevered "ruler" of a short length compared to a longer length.
Now on the face of it, this all seems reasonable and is certainly true of a pure cantilever.....
But a tonearm with the cartridge resting on the record is NOT a pure cantilever.
It is a PROPPED cantilever and all the Bending Moments, Shear Stresses and Deflections are entirely different (and change with the degree of VTF on the stylus) to that of a pure cantilever.
So the SAT arm has been designed by Marc Gomez as a tapered tube (from pivot to cartridge) which mirrors the stresses of a pure cantilever much like other tonearm designers like SME have also done.

Continuum Audio Labs with their Cobra and Copperhead tonearms utilised a team of qualified University Experts with access to advanced software and technology to model the arms using NASTRAN, PATRAN and DYSTRAN finalising in the complex process of Gradient Shape Optimisation using Reshape.
View attachment 41628

THIS is the true shape of the stresses involved in a 'Propped Cantilever' and the true shape for maximum RIGIDITY for that application.
The SAT tapered tube is NOT the correct shape for maximum rigidity of a propped cantilever whether it's 9" or 12".

Now I'm not denying Michael, that you prefer the SAT on your Caliburn over the Cobra......but I'm pretty sure it's not because the SAT is more rigid than the Cobra.
And if Mark Gomez can make an elementary mistake on physics....his justifications for 9" over 12" are suspect IMO.
If you compare the shape of the Cobra and Copperhead arms to the SAT (and also the Kuzma 4 point and SME)......you will find that a simple 'tube' more closely approximates the shape of the Copperhead than that of the SAT.
And if you look through the history of tonearms and study the slenderness ratios of some of the tube tonearms throughout the decades........the Moechs, the Hadcocks, the long Micro-Seikis and SAECs let alone the Shroeder tonearms... would never pass the first listening test if Marc was correct about his theory of rigidity.

A tonearm only has to be rigid enough for the purpose.
It's like a structural engineer telling a client he can make his floor more rigid if the room were 10 foot wide instead of twenty......
Most tonearms are rigid enough....
There are other reasons you find the SAT arm so superior

Henry

You a gem

I have spent the afternoon on a mathematical model of this tonearm engineering problem

I didn’t read your comment till just now

Clearly the model is much more than a simple lever issue, the fact of the cartridge adds to the whole system

Rigidity is a factor but fundamentals of the entire system far outweighs any secondary factors like rigidity, or mass

Although I haven’t finished my modelling yet, what can be said so far is mass and rigidity will only move the frequencies of resonance around, they cannot remove them

It’s really an interesting engineering issue ?

There was an interesting non engineering but thoughtful review in TNT which pointed out the resonance in the SAT was pushed out to 2.8khz

I don’t know the basis of this commentary , but it’s intersting as it’s double that of other popular tonearms

It does seem we have an interesting issue, as there is a optimal engineering solution, which is probably a compromise of competing engineering solutions and then the aural perception which may or may not coincide with the optimum solution , ie resonance versus system perception aurally , which technically should feedback into the engineering solution

On a real world level, aren’t both the SAT AND Calibrun arm 9 inch?

And MF has owned or tested both and prefers the former is that correct ?

 

[PeterA]

I am glad we have a new thread on this very interesting subject. Has anyone besides Marc Gomez directly compared the 9" and 12" versions of his two arms? He does mention the possibility that the longer arm may be preferred by some listeners. If that is the case, and he claims the 9" is more accurate, he is saying that some listeners will prefer the less accurate sound of the longer arm.

I would still like to know what the effective masses of the various SAT arms are and how these compare to other successful tonearm designs. If effective mass which affects the moment of inertia of the arm is of primary important, than the weight of the cartridge surely matters. If reducing moment of inertia is so important, I would think that we would all prefer very light cartridges mounted on the far ends of these propped cantilevers. However, light cartridges may not dampen the vibrations from the cartridge enough and those vibrations will move into the arm wreaking their havoc. This then requires the arm to better dampen those vibrations. This is one reason the arm/cartridge pairing/match is so important.

What matters is the integrity of the whole cartridge/arm/armboard/mounting system, the interactions of the various components to each other and how this system deals with the vibrations inherent in vinyl playback. I wish I knew more about the science involved.

Halcro, I think, made the very interesting comment that the arm has to be just rigid enough. If that is the case, then once an arm is rigid enough, and some 9" arm/cartridge combination has the same moment of inertia at a longer am/cartridge combination, due to cartridge weight and the overall effective mass of the system, then wouldn't tracking error be area where sonic differences become audibly meaningful, assuming a well mounted stylus, straight cantilever and proper alignment setup ?

 

[microstrip]

I am glad we have a new thread on this very interesting subject. Has anyone besides Marc Gomez directly compared the 9" and 12" versions of his two arms? He does mention the possibility that the longer arm may be preferred by some listeners. If that is the case, and he claims the 9" is more accurate, he is saying that some listeners will prefer the less accurate sound of the longer arm.(...)

I also noted that he used the word accurate to compare the tonearms. Considering that we never manage to have a consensus on the meaning of accuracy, and high-end vinyl sound reproduction is not supposed to be accurate, should we consider that he was considering some kind of measurements?

Anyone can carry similar comparisons easily. Some eBay vendors sell 9" and 12" replacement tubes for SME3009 cut to dimension - the poor man SME 12" . However such comparisons are meaningless, as probably a tube of different material or thickness will have different resonances and will give different results.

 

[awsmone]

I also noted that he used the word accurate to compare the tonearms. Considering that we never manage to have a consensus on the meaning of accuracy, and high-end vinyl sound reproduction is not supposed to be accurate, should we consider that he was considering some kind of measurements?

Anyone can carry similar comparisons easily. Some eBay vendors sell 9" and 12" replacement tubes for SME3009 cut to dimension - the poor man SME 12" . However such comparisons are meaningless, as probably a tube of different material or thickness will have different resonances and will give different results.

To be honest I don’t know what from an engineering point of view is meant by “accurate”

This would need to be defined

Accurate tracking
Frequency response
Harmonic distortion
Enharmonic distortion
Etc

The statement in and of its own is meaningless

I await some verifiable data on such an assertion , hopefully it will be forthcoming

 

[awsmone]

To be honest I don’t know what from an engineering point of view is meant by “accurate”

This would need to be defined

Accurate tracking
Frequency response
Harmonic distortion
Enharmonic distortion
Etc

The statement in and of its own is meaningless

I await some verifiable data on such an assertion , hopefully it will be forthcoming

I am glad we have a new thread on this very interesting subject. Has anyone besides Marc Gomez directly compared the 9" and 12" versions of his two arms? He does mention the possibility that the longer arm may be preferred by some listeners. If that is the case, and he claims the 9" is more accurate, he is saying that some listeners will prefer the less accurate sound of the longer arm.

I would still like to know what the effective masses of the various SAT arms are and how these compare to other successful tonearm designs. If effective mass which affects the moment of inertia of the arm is of primary important, than the weight of the cartridge surely matters. If reducing moment of inertia is so important, I would think that we would all prefer very light cartridges mounted on the far ends of these propped cantilevers. However, light cartridges may not dampen the vibrations from the cartridge enough and those vibrations will move into the arm wreaking their havoc. This then requires the arm to better dampen those vibrations. This is one reason the arm/cartridge pairing/match is so important.

What matters is the integrity of the whole cartridge/arm/armboard/mounting system, the interactions of the various components to each other and how this system deals with the vibrations inherent in vinyl playback. I wish I knew more about the science involved.

Halcro, I think, made the very interesting comment that the arm has to be just rigid enough. If that is the case, then once an arm is rigid enough, and some 9" arm/cartridge combination has the same moment of inertia at a longer am/cartridge combination, due to cartridge weight and the overall effective mass of the system, then wouldn't tracking error be area where sonic differences become audibly meaningful, assuming a well mounted stylus, straight cantilever and proper alignment setup ?

Your correct Peter in pointing out that the tonearm forms part of a bigger mechanical system which includes a cartridge of variable mass and compliance

In addition this forms part of an electrical circuit , where the loading will effect compliance and this will effect frequency response

An argument could be made that if all these parameters are kept constant then we can just talk about the arm itself

In reality all these elements will play a factor, even from an engineering point of view before perception

 

[rockitman]

Well it may be true that Marc Gomez has a Mechanical Engineering Degree and studied materials science....but reading his 'explanations' for the 9" preferred tonearm length.... he seems to lack the necessary Structural Engineering qualifications to complete the picture...?

He includes a diagram titled "Effect of length in vibration amplitude and frequency" and shows a diagram (and speaks of) a cantilevered "ruler" of a short length compared to a longer length.
Now on the face of it, this all seems reasonable and is certainly true of a pure cantilever.....
But a tonearm with the cartridge resting on the record is NOT a pure cantilever.
It is a PROPPED cantilever and all the Bending Moments, Shear Stresses and Deflections are entirely different (and change with the degree of VTF on the stylus) to that of a pure cantilever.
So the SAT arm has been designed by Marc Gomez as a tapered tube (from pivot to cartridge) which mirrors the stresses of a pure cantilever much like other tonearm designers like SME have also done.

Continuum Audio Labs with their Cobra and Copperhead tonearms utilised a team of qualified University Experts with access to advanced software and technology to model the arms using NASTRAN, PATRAN and DYSTRAN finalising in the complex process of Gradient Shape Optimisation using Reshape.
View attachment 41628

THIS is the true shape of the stresses involved in a 'Propped Cantilever' and the true shape for maximum RIGIDITY for that application.
The SAT tapered tube is NOT the correct shape for maximum rigidity of a propped cantilever whether it's 9" or 12".

Now I'm not denying Michael, that you prefer the SAT on your Caliburn over the Cobra......but I'm pretty sure it's not because the SAT is more rigid than the Cobra.
And if Mark Gomez can make an elementary mistake on physics....his justifications for 9" over 12" are suspect IMO.
If you compare the shape of the Cobra and Copperhead arms to the SAT (and also the Kuzma 4 point and SME)......you will find that a simple 'tube' more closely approximates the shape of the Copperhead than that of the SAT.
And if you look through the history of tonearms and study the slenderness ratios of some of the tube tonearms throughout the decades........the Moechs, the Hadcocks, the long Micro-Seikis and SAECs let alone the Shroeder tonearms... would never pass the first listening test if Marc was correct about his theory of rigidity.

A tonearm only has to be rigid enough for the purpose.
It's like a structural engineer telling a client he can make his floor more rigid if the room were 10 foot wide instead of twenty......
Most tonearms are rigid enough....
There are other reasons you find the SAT arm so superior

Very interesting Henry. Thanks for the explanation. It makes logical sense.

 

[spiritofmusic]

So, we await the SAT 9” v 12” on the same tt, sporting the same carts, and whatever the outcome is.

Or maybe this won’t happen.

 

[ddk]

So, we await the SAT 9” v 12” on the same tt, sporting the same carts, and whatever the outcome is.

Or maybe this won’t happen.

Marc,
There's an SAT going on nearly every AS-2000 sold in the Far East bot 9" & 12" models and I can tell you that for the most part people spending the money on these arms do NOT care about any of this@! I happen to disagree with Gomez about the 9" vs 12" universally but I support and respect his opinion when it comes to his own designs. He's very candid about the 12" SAT tonearms and where he stands, you have to admire that and give the man credit for it.

david

 

[spiritofmusic]

Dave, I thought the AS2000 was a VERY limited production run, just to the guys we know about and maybe Billy the “ultimate playboy”.

Have you extended the run to a few more?

 

[NorthStar]

Is there a bible for analog music reproduction with the most and best accurate tonearm? Are there some computer measurements somewhere?

The paper from Marc is very clear; a 9" tonearm is more accurate than a 12" one.

I know that you guys are like me and don't believe in analog music measurements and simply enjoy the music playing in the most pleasant delivery possible always. There are no limits between 9 and 12, shorter and longer.

The 9", from what I'm reading, is the guide but not an ultimatum, or this hobby would be real boring.
For high caliber vinyl spinners it's not a sin experimenting and preferring less accuracy in their passion for analog music listening.
For new comers and beginners, would it be the same? Or would it be best starting with accuracy first (9")?