High mass tonearms

[Darren L]

Having never owned a high mass tonearm I wonder what's the difference between a high mass arm coupled with a low compliance cartridge in comparison with the lower mass arms?
I've been looking at the Groovemaster/Timestep and Thomas Schick tonearms, I understand a lot of these arms may be used with an SPU but used with the correct head shell [weight wise] and a compatible low compliance cartridge what's the difference, do they have a particular sonic signature?

 

[Vinny]

I don't know the answer but a high mass arm is going to force the cart' suspension to do a lot more work. That is inevitable because the moment of inertia of the arm will always be 1-2 orders of magnitude higher than the cart' suspension, (more than) partially negating any differences in the cart' compliance. Compatibility cart'/arm is essentially to do with resonances, not the mechanics of how the pair work together in tracking a groove and the modulations in it.

Some slick software would answer the conundrum PDQ. but my GUESS would be that tracking would be worse, at some, probably minute, scale.

Imagine the system as two springs, the tonearm being substantially more rigid, then make it more rigid by increasing effective mass. Not a great analogy, but maybe good enough.

I'd be interested to hear experiences, or to see see some real maths..................

Very easily tried - add some mass to the headshell of a tonearm.

 

[Elephantears]

I recently got a FR64S for my Miyajima Takumi. The Takumi is low to medium compliance, so it doesn't absolutely demand a high mass arm. However I've always felt I could improve on tracking, even with the very good 12" Ace Space I was using.

At first I was using a very high mass head shell, and I found the sound was very clear but bass heavy. Dynamics were somewhat overblown. I changed to a lighter head shell and even then it took some time to get the set up right. Getting good alignment was relatively easy, but I spent much more time than I've ever done before fine tuning the VTF and VTA. I'd read some opinions suggesting the FR arms were all about dynamics and guts, and for a while I was a bit worried that I'd moved too far in that direction. However I finally nailed the set up and have found it a really well balanced and neutral arm that works across the musical spectrum. It is just as good with the tonality of jazz recordings as my 12" Ace Space, but it has greater dynamic projection. With rock music it is fantastic; I've been listening to a lot more since I got it.

 

[Mike Reed]

The Groovemaster/Timestep arms are around 22g, so higher medium mass in context. My only knowledge of this, and one which is driving my thoughts of changing one of my arms, is that very low compliance carts like Koetsu and most certainly some Miyajimas, are far more synergistic with a higher mass arm; say, 18 to 30g. Many coils are lowish compliance but don't necessarily demand a very low mass arm.

My Proteus is very happy in my circa 14g PU7 . My Benz was as well. My Urushi sounded fine in my SME Five (11g) before I went 12", but sounded better in my current arms, though I have that feeling it could be better still. The mathematics of arm/cart. synergy are well documented even if a bit beyond my feeble brain, but I don't question them. There's obv. flexibility, but a perfect arm match may be limiting for some cart's and a more practical compromise arm won't be perfect (sigh!).

I've been looking at viable 12" arms recently, both unipivot and gimbal, and find that silly little design flaws like a difficult, inefficient or even an abrasive arm rest/clip put me right off.

 

[sonddek]

I'm currently developing an arm which I hope to be selling within a few months, and I have opted to make it as low mass as possible, because inertia is like salt - easy to add, but difficult to remove. I will supply the arm with a movable weight for the cartridge end of the arm so that users can apply higher inertia for any low compliance cartridge which needs it. This is nothing new: Technics supplied screw-in headshell weights.

A high mass arm would seem to me to be needlessly excluding a wide range of very good high-compliance cartridges when a blu-tacked tuppence would solve the problem.

If a heavy arm's additional mass were dedicated to rigidity and better bearings there might be cause, but that seldom seems to be the case.

 

[Howdy]

... in my circa 14g PU7...

14g of PU7 surprised me, especially compared to Kuzma Stogi S, Stogi, Stogi Ref, 4Point 9 at 11, 12, 13 and 13g respectively.
Then I saw that AO offers PU7 "tuned to your selection of cartridges approx. 11–20 grams".

Another surprise was that Roksan states 15.3 g for Nima at https://www.roksan.com/en/product-ranges/nima/nima-tonearm/
but 11g - which seems more plausible - in tonearm manual:
https://www.dropbox.com/sh/6b5sfd11...KaaQYl7a?dl=0&preview=NIMA+Tonearm+Manual.pdf

Regarding low compliance carts, not only that you need high mass arm, you probably also want them on EMT or Garrard, not on belt driven deck. And if on belt drive, only on extremely high mass platter.

 

[Darren L]

Regarding low compliance carts, not only that you need high mass arm, you probably also want them on EMT or Garrard, not on belt driven deck. And if on belt drive, only on extremely high mass platter.

Interesting, so why not a belt drive? If the cartridge is tracking at say 2.0g, regardless of the compliance of the cartridge or effective mass of the tonearm why would it matter what drive system the TT uses?
I do see quite a few idler drive TTs (mainly Garrard 301 & 401) combined with high mass arms.

 

[Howdy]

Interesting, so why not a belt drive? If the cartridge is tracking at say 2.0g, regardless of the compliance of the cartridge or effective mass of the tonearm why would it matter what drive system the TT uses?
I do see quite a few idler drive TTs (mainly Garrard 301 & 401) combined with high mass arms.

The drag/resistance the low compliance cart causes is significantly higher then with high compliance cart, regardless of tracking force/weight.
You could also measure that by spinning TT platter (without belt attached) by hand, placing the stylus on the record and timing how long does it take for platter to stop with different carts.

Think of TT cartridge in the record groove as if you're pulling a shopping cart by a rubber band over tiled flooring, and driving it over some small obstacles on your way.

 

[Vinny]

The drag/resistance the low compliance cart causes is significantly higher then with high compliance cart, regardless of tracking force/weight.

There are myriad assumptions involved in getting to that conclusion, and I am disinclined to beleive the conclusion. That apart, the drag of the cart' is going to be, at all times, all circumstances, all compliances etc., smaller than miniscule compared to the moment of inertia of even a light spinning platter.

 

[sonddek]

If the different downforces/compliances are audible when the spinning platter is undriven, and they are, because the platter really does slow more quickly, is there a chance that they are audible when driven? I think so. Think of the energy stored in your belt, smearing pace and melody over seconds as the signal-drag ebbs and flows.

The claim that these liminal factors are inaudible is also based on many uncertain assumptions, assumptions which turntable makers do not make when considering mass, power, and friction.

Low down-force and low drag are good in many ways. Low inertia arms with high compliance cartridges have many advantages.

 

[Vinny]

Low inertia arms with high compliance cartridges have many advantages.

I am unconvinced at the level of a simplistic statement.
Effective mass of the tonearm is really inertia, which is related to compliance. Avoiding certain combinations of cart' compliance and effective mass is to avoid resonances - the assembly is directly analagous to two springs connected together, albeit one spring something like a car suspension spring and the other in comparison, like that in a retractable ball-point.

I have been through the maths before - I wish that I'd kept them - but the compliance of a cart' is something like two orders of magnitude higher than that of the tonearm - so the cantilever will be prone to move FAR more than the tonearm.

Coming back to the effect of friction/drag and how it changes as the sylus reads the modulations within the groove - show me some evidence/maths that suggests that it amounts to more than the tracking force. Friction alone is reckoned to be around 0.6 times the tracking force - so less than a gramme in most circumstances. Now apply that figure as resistance to the movement of a rotating body of a few 100g, or more.

As for this "give the platter a spin" time it until it stops and compare...............................I only wish that I had a set of calibrated arm muscles.

 

[awkwardbydesign]

but the compliance of a toenarm is something like two orders of magnitude higher than that of the cart' - so the cantilever will be prone to move FAR more than the tonearm.

Is that the right way round?

As for this "give the platter a spin" time it until it stops and compare...............................I only wish that I had a set of calibrated arm muscles.

Use a strobe disc, spin a bit faster than 33rpm, but time it from 33rpm.

 

[Vinny]

Is that the right way round?

Correct - good spot. Now corrected.

 

[sonddek]

I thought the distinction between arm-cartridge combinations is more about at what frequency you want the inevitable resonance to occur. Around 13 Hz is allegedly the design goal - is that logarithmically half way between 5/9Hz (warps & eccentricities) and 20Hz, the audibility threshold? It's an imperfect world.

Theoretically the cartridge will perform best (most linearly) when the cantilever is at the equilibrium playback position, not just by design, but because deflection has non-linear geometry. Significant net excursions up, down, left or right will degrade aspects of signal retrieval, including, but not limited to channel balances, tracking, rake angle. That's why a good arm is rapidly shifted to the new equilibrium position by the cantilever with ease as the warp goes by, and by warp I don't necessarily mean something visible - we are thinking at the thousandth of a millimetre scale, remember.

If your cartridge-arm system's resonant frequency is in the 10-13Hz range, that's the best you can hope for and will provide enough inertia for low bass, while shifting the arm to accommodate warps/eccentricity without excessive cantilever deflection.

As I said above, records and styluses last longer if you can get a good sound and a 13Hz resonance peak at low down-forces with no mistracking.

 

[Vinny]

I thought the distinction between arm-cartridge combinations is more about at what frequency you want the inevitable resonance to occur.

I think that that is effectively what I said - should have included "troublesome" or "unwanted" perhaps?

Theoretically the cartridge will perform best (most linearly) when the cantilever is at the equilibrium playback position

I am unsure that that is correct, but either way it is set by cart' compliance and tracking force and we all tend to go with recommended tracking force, so something of an irrelevant point, perhaps.

Significant net excursions up, down, left or right will degrade aspects of signal retrieval, including, but not limited to channel balances, tracking, rake angle. That's why a good arm is rapidly shifted to the new equilibrium position by the cantilever with ease as the warp goes by, and by warp I don't necessarily mean something visible - we are thinking at the thousandth of a millimetre scale, remember.

The first bit will be a question of degree, not as black and white as you imply. Any arm is deflected by virtue of the cart' compliance and tonearm effective weight, nothing to do with "good" and certainly "rapidly" is another misleading term as, at the end of the day, the tonearm, compared to the cantilever "does not want to move".

As I said above, records and styluses last longer if you can get a good sound and a 13Hz resonance peak at low down-forces with no mistracking.

Source for that "fact"? The only published data about wear of stylii that I have seen was produced quite some years ago by one of the very famous brands - Ortofon (????), but was a study on VERY different stylus profiles to the ones that we use today. It is an age since I skim-read it, so have no real recollection about its contents.

 

[sonddek]

I am unsure that that is correct, but either way it is set by cart' compliance and tracking force and we all tend to go with recommended tracking force, so something of an irrelevant point, perhaps.

Well, we all have the odd record with a bit of a warp. Cantilever suspensions are finite, with diminishing elasticity near their operational extremes because they are made with real, not theoretical materials. With a heavier arm, more time after warps will be spent nearer those extremes. Isn't this just common sense?

The first bit will be a question of degree, not as black and white as you imply. Any arm is deflected by virtue of the cart' compliance and tonearm effective weight, nothing to do with "good" and certainly "rapidly" is another misleading term as, at the end of the day, the tonearm, compared to the cantilever "does not want to move".

The inertia of the tonearm will certainly affect the length of the period taken to return to equilibrium after being deflected by a warp, all other things being equal. A responsive arm-cartridge system will be critically damped, and arm inertia has a big effect on the Q factor.

Source for that "fact"? The only published data about wear of stylii that I have seen was produced quite some years ago by one of the very famous brands - Ortofon (????), but was a study on VERY different stylus profiles to the ones that we use today. It is an age since I skim-read it, so have no real recollection about its contents.

More pressure at the stylus contact point will increase both stylus and record wear. This is such an obvious and well-established feature of real-world surfaces in friction, that I'm surprised it is being questioned. The evidence that it happens is easily visible when you examine long-used diamond styluses under a microscope. Again, common sense - no need for dispute.

 

[Vinny]

Isn't this just common sense?

Entirely, but any entrapolation from that indisputable fact, is not, it is pure supposition.

More pressure at the stylus contact point will increase both stylus and record wear. This is such an obvious and well-established feature of real-world surfaces in friction, that I'm surprised it is being questioned. The evidence that it happens is easily visible when you examine long-used diamond styluses under a microscope. Again, common sense - no need for dispute.

I strongly suggest that you search out the paper produced by Ortofon(?), and read and understand it.