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Tonearm “rigidity”: beliefs, myths and revisionism

Tony L

Administrator
I notice a distinct backing away from the ‘80s flat-earth ideology of what Linn described as a ‘closed loop’ between cartridge and main bearing and where the word ‘rigid’ was used in most sentences by reviewers, dealers and even customers. Over the past few years it appears things are changing and cartridge ‘isolators’ are back in vogue with offerings from The Cartridge Man, Funk Firm and Origin Live.

I find this all pretty interesting as for over 20 years now I’ve questioned and largely rejected the whole concept of “rigidity” as most audiophiles seem to understand it, and find most things (arms, cartridges, speaker drivers etc) sound demonstrably worse if tightened beyond the point where they are merely secured. I use the ‘cracked bell’ or ‘drum’ analogy; that the last thing you want is a tuned resonance, something that behaves like a tuning fork or conga drum. I strongly suspect this is one reason so many of my favourite speakers have screwed baffles (a broken bell doesn’t ring). It was Tom Fletcher of Nottingham Analogue who planted this idea with me at a long chat at a hi-fi show back in the ‘90s. His attitude was things needed to be just tight enough to stop them falling apart, but no more. Since that point I have listened and set things by ear. I have a sufficient grasp of physics to grasp nothing is rigid in any real sense and really all you are doing is modifying resonance in some way.

As such I’m interested to see these products emerging as to my mind they make some sense in that they may be preventing the arm and cartridge from behaving as a tuned resonant structure. My best guess is they are ‘breaking the bell’ the way a BBC-style screwed baffle and back door on a speaker cab appears to.

PS As I’ve followed the ‘loose is the new tight’ approach for a long time now my cart (a MP-500) is attached to the SME shell using the Nagaoka supplied plastic washers and with a little blob of Blu-Tac just under the SME logo to dampen the shell and effectively give a three-point fitting (vintage SME shells have a very small contact area, especially if you use the finger-lift, so this is a definite gain). Nothing tight, nothing free, it all exists somewhere deliberate between those points. I like the classic aesthetic of the arm with its shell too much to use a “better” one, but it would be interesting to try at some point with felt decoupling and I’m certainly curious to know if many have experimented with these type of isolation products, especially if you are using them with 1980s “rigid” tonearms (Linn, Rega, Mission, Zeta etc), i.e. effectively kicking that whole ‘closed loop’ ideology into the weeds!
 
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I notice a distinct backing away from the ‘80s flat-earth ideology of what Linn described as a ‘closed loop’ between cartridge and main bearing and where the word ‘rigid’ was used in most sentences by reviewers, dealers and even customers. Over the past few years it appears things are changing and cartridge ‘isolators’ are back in vogue with offerings from The Cartridge Man, Funk Firm and Origin Live.

PS As I’ve followed the ‘loose is the new tight’ approach for a long time now my cart (a MP-500) is attached to the SME shell using the Nagaoka supplied plastic washers and with a little blob of Blu-Tac just under the SME logo to dampen the shell and effectively give a three-point fitting (vintage SME shells have a very small contact area, especially if you use the finger-lift, so this is a definite gain). Nothing tight, nothing free, it all exists somewhere deliberate between those points. I like the classic aesthetic of the arm with its shell too much to use a “better” one, but it would be interesting to try at some point with felt decoupling and I’m certainly curious to know if many have experimented with these type of isolation products, especially if you are using them with 1980s “rigid” tonearms (Linn, Rega, Mission, Zeta etc), i.e. effectively kicking that whole ‘closed loop’ ideology into the weeds!

As a Cartridgeman Isolator tester/user for 20 years I could not agree more.
 
Interesting that the Funk approach apparently combines isolation with rigidity of the tonearm itself. I’n a fan of their FXR and wouldn’t mind trying the Houdini.
 
I'm using a wand which has the headshell and counterweight held in place only by tight o-rings, there's no rigid or hard connection. It's been a very successful way to decouple the cartridge.
 
A Decca with its plastic mount on a magnetically suspended damped unipivot springs to mind. Like mine. Seems to work.

An excellent case in point. That plastic mount has been ridiculed from here to hell and back for decades, but I read an excellent article a few years ago (can't find it now) that argued that Decca new exactly what they were doing.
 
I've not thought about this before, but neither have I ascribed to the 'tighten the cart. until you squeak' philosophy. To me, it's a choice of isolating the cart. from the arm or ensuring it's part of the arm, esp. with fixed head-shells. I guess it's worth experimenting, but wouldn't a simple thin layer of rubber (or similar) twixt cart. and h/shell do the trick?

I guess that if you introduce a damping layer, azimuth could be affected slightly and this could be tricky for arms without azimuth adjustment. Rubber washers under the screws? This would theoretically create an air pocket between cart. and shell. Sounds a bit iffy to me. Would decoupling in any way benefit all cart's, I wonder, or indeed, all materials which form cart. bodies.
 
I visited Len one afternoon about 25 years ago for an afternoon’s audition of his cartridge on a prototype Air Forcell parallel tracking arm/SpaceDeck. His Musicmaker had isolation material on both sides of tone arm head and he advised to just ‘nip up ‘ the bolts. The material covers about 60% of the cartridge top face despite the headshell being large enough to accommodate it 100%.
I’ve still got the outfit which I’m about to reinstall after a few years following other interests.
 
Did you know Len Gregory? If so did he give any explanation as to his logic/thinking?

Yes I knew Len we became friends over 20+ years after I bought a Musicmaker mk1, we both got on; as it was a 120 mile round trip to Southbridge Road via M25 we mostly spoke on the phone, I visited to pick up things to test for him or he posted them I do not believe Len was ever convinced regarding absolute rigidity ie closed loop, over time working on not only cartridges but other projects he concluded in a closed loop system the energy created could not be destroyed of course it was on a par to the miniscule stylus movement creating unwanted interference at the interface ie stylus tip both summing and cancelling with the wanted signal unpredictably affecting the cartridge electrical output, by breaking this loop the cartridge output was almost just the stylus grove contact.

People have often written that his cartridges were just Grado's in fact he made everything inside like a Grado it was a Moving Iron creating much less tip mass than MM or MC the Grado body he bought the rights from Joe Grado because it was the most inert body he could find, he was unable to better it over 20 odd years despite spending a lot of money searching .

Even the foam used in the Isolator was not just sponge if compressed it would not spring back some came from the auto industry some was from MRI and other medical scanning equipment to absorb prevent vibration to promote accuracy.

I miss my friend.
 
I only have experience of the Isolator the bottom of which is stuck to the top of the cartridge then the foam another stainless layer to which the fitting bolts are attached so that the bolts do not track vibration through.
 
I have some offcuts of thin sheets of PEEK. It’s not bad at damping vibrations. I might cut myself a gasket and try it. VPI tonearm, so will be easy to adjust the VTA afterwards.
 
There is of course no such thing as absolute rigidity. Any mechanical circuit such as the ‘closed loop’ will be resonant to a lesser or greater degree. The art of arriving at the best compromise is not well-defined, but starting from making everything as rigid as possible is no less valid than making things floppy.
I’ve done more measurements on tonearm resonance than I care to remember, and every combination of arm/cartridge/deck is different. It’s a subjective choice, like everything, but I tend to settle on simple unipovots, with very little damping anywhere. In that respect, I tend to veer away from using damped materials, as they can be very non-linear.
All record decks are musical instruments, not transcription devices IMO.
 
I'm very interested in this question, especially in reference to building my tonearm. I suppose my intuition came from comparison of many cartridges on an Ekos 2, Well Tempered Arm and a pair of SME 3009 ii. While the Well Tempered Arm was smooth and quite detailed, the Ekos seemed to have an edge on detail and punch - it holds my attention better.

I couldn't help feeling that the damped and less than rigid design of the Well Tempered was robbing the signal of some dynamics and detail by absorbing energy, which originates in the interaction between stylus and record surface, and whose undissipated transferance is the raison d'être of the system.

I decided that dynamics, punch and detail are more important than complete suppression of resonance, so I set out to design and build the most rigid tonearm I could. Obviously I would say this, but I find the detail, dynamics and irrepressible energy of my design mesmerising and I'm surprised at how well this theorising has converted into the music I'm hearing. I have never enjoyed vinyl so much in 40 years of listening. It is just punchier, deeper, more detailed and more urgent than I've heard before, and I do attribute the irrepressible energy of recordings to high rigidity.

It seems to me that rigidity is not a source of resonance, but is the primary strategy for suppressing resonance and colouration, as well as retrieving the full power of the recorded signal.

Over-tightening bolts may not be the best way to achieve higher rigidity and may introduce unwanted consonance, but equally I struggle to understand how increasing flexibility is going to lead to a lesser addition of resonance to the signal.

It seems to me that an ideal cartridge/tonearm/platter-bearing system will first provide a rigid platform for the cantilever to do its work, and secondly attempt to minimise resonances in the mechanism/structure by appropriate choice of material and structure.
 
It seems to me that an ideal cartridge/tonearm/platter-bearing system will first provide a rigid platform for the cantilever to do its work, and secondly attempt to minimise resonances in the mechanism/structure by appropriate choice of material and structure.
Well, the first is not possible, and secondly, bear in mind that some resonances sound nice :)
 
Thinking about it a little more it may make sense to consider bolt-tightness (the Tom Fletcher approach etc) as something distinct from isolation, as I think it is. As stated I’ve followed this approach for a very long time now, but to my mind it isn’t losing rigidity or adding compliance, it is just preventing ringing and resonance. As an example if you want to make vintage Tannoys sound the way people on the internet who hate them think they sound simply over-tighten the driver basket to the baffle. The bass goes away, they generate a peaky harsh treble and basically sound like crap. I know as I’ve done it! I really killed the sound of my first pair for a while as I snugged the bolts up a quarter turn from where they were and it took me some time to figure out why what once sounded effortless, natural and easy now sounded pinched, forward and over-analytical. The ‘before’ state wasn’t ‘loose’, there was no play, nothing was rattling about or anything, they just weren’t tuned up like a drum-head. As such I’m reluctant to describe it as ‘isolation’.

I’ve since learned a lot about where they sound best, and one thing I’ve found very interesting is this level of ‘only gently snug’ seems applicable across so much of my hi-fi, e.g. I have the arm-board of the 124 just attached to the point the three machine-screws stop. It’s certainly attached, nothing rattles, but it is at what I assume is its most damped point. Go beyond this and the sound starts to take on a pinched and forced sound, loosen it further and things start to sound muddy and the rhythmic drive starts to be lost.

It has been known for a very long while that the old Rega Planar 2 and 3 sound better with the big arm base nut just gently nipped-up to the point you can still use the cueing arm without the armbase moving, but no more than that. I strongly recommend trying that if you have one of these decks, or a deck with an RB250-300. Just tight enough so you can still use the cueing arm! I’m at the point now where I actually listen to every screw tension that is involved in an electromechanical transducer. It unquestionably repays the effort.

Speaker stands too. Just tight enough so they don’t move or rattle. If I could get rid of spikes I would, but they just make sense on thick carpeted floors to hold things in place level the speaker. I guess the closest to actual ‘isolation’ I use is fairly thick felt pads on the top of speaker stands (for the 149s and LS3/5As, the Tannoys are flat on the carpet, so I guess a similar approach, but that’s mainly because I can’t lift them!).

This is a bit of a rambling post, but I’m curious about the conceptual differences between avoiding resonant peaks, damping, and isolation. They are clearly all different things and I suspect we are not limited to an either/or here. Another thing from a basic physics perspective is the classic audiophile error of assuming because something looks and feels “rigid” or “flimsy” when you are holding it in your hand that it is so at audio frequencies. I’ve heard some truly laughable marketing guff over the years that doesn’t stack up to even the slightest scrutiny, but electromechanical transducers are complex things that never exist in isolation. They are all part of a larger logical structure and changes at every point are easy to hear so I advise playing around.
 
I couldn't help feeling that the damped and less than rigid design of the Well Tempered was robbing the signal of some dynamics and detail by absorbing energy, which originates in the interaction between stylus and record surface, and whose undissipated transferance is the raison d'être of the system.

I’m prepared to bet that at audio frequencies the Well Tempered is vastly more rigid than the Ekos and what you preferred was actually a resonance! Any arm with bearings has slop, if it didn’t it couldn’t move, i.e. even the high quality bearing races Linn use will have movement in every plane. My theory is this is why the Aro, which being a unipivot does not have slop, sounds much smoother and more open across the midband to my ears.
 
I suspect the recommendation 'tight' didn't mean murdered. But with a high OCD hobby it was probably enough to get baffles distorted, cartridge lugs crushed and threads stripped countrywide. :)
 
I suspect the recommendation 'tight' didn't mean murdered. But with a high OCD hobby it was probably enough to get baffles distorted and threads stripped countrywide. :)

I’ve seen dealers who have been on Linn “training” courses absolutely butcher kit. Watching one set up a friend’s LP12 back in the ‘80s was the point I started insisting on doing everything myself. I suspect the vast majority of big dents you find in the VTA adjustment on Ittoks (which can easily destroy the lateral ball races) were done by dealers. Very few people who had paid £3-400 for an arm would actually do that level of damage themselves! Same with all the ugly chewed-up headshells. I’ve watched it happen first hand! Rega and others learned from this and supply a torque wrench, which is not high-torque at all (I can’t remember the exact Nm figure, but it isn’t much at all on a Linn dealer scale!).
 
I can remember being told to check the fasteners holding the drivers in place and indeed after a period of time they had become loose, I never had anyone give any advice or indeed even read anything about how tight cartridge fasteners need to be but then I didn't buy a Linn.
To be honest I've never really given it much thought but always would be very careful when installing tonearms or cartridges, just really tight enough to hold either the tonearm or cartridge in place but not over tight, afterall they're pretty delicate items.
 


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