Tonearm “rigidity”: beliefs, myths and revisionism

[Sue Pertwee-Tyr]

That weren't foam lad, that were small Eccles cakes.

Pontefract cakes, surely? Eccles is in That Lancashire, and therefore beyond the pale to A True Yorkshireman

 

[flatpopely]

Please show your evidence! I’m not singling out Linn, it is the same with any conventional bearing arm. If they had no play they can’t move freely, simple as that. Sure, humans won’t be able to feel any slop in an ABEC 5 or 7 bearing, but it is there on a microscopic level as it has to be for the thing to have low friction. This is not the case on a unipivot, a WT, Schroeder and some other non-conventional designs. These work with a different rule-book.

PS FWIW the old Linn arms have a distinct sound to my ears; the Ittok having a pretty obvious resonance/forwardness in the upper mid (the reason I later went to a Zeta), fun and very tuneful though. I never got on with the Ekos in dems, very easily beaten by the Aro to my ears/taste, though in fairness I never heard the MkII.

The contact between the ball bearings and the race are probably less than the point contact on a unipivot.

 

[AndyU]

It seems to me to be a matter of principle that ideal transducers in an ideal environment will be fixed firmly to minimise the 'doppler effect' caused by parts moving when they shouldn't.

Not sure I agree as far as speakers are concerned, at least for some kinds of floors. Why would you want couple a speaker into a wooden floor which will radiate sound, and through which sound will travel faster than air? Speaker designer has done a lot of work making the speaker radiate sound; why mess it up by connecting your floorboards? The sort of stands Northward are offering for (typically) ATCs are well coupled to the floor for stability, but then decoupled from the speaker above about 8Hz. Highly damped fore and aft and against rocking.

 

[sq225917]

The contact between the ball bearings and the race are probably less than the point contact on a unipivot.

A radius is a radius, assuming infinite smoothness and hardness they're all but identical, except a gumball ball race tonearm has 10-20 times more of them and steel is way softer than sapphire. There's no comparison the uni is an order of magnitude lower in contact sutface

 

[Tony L]

A radius is a radius, assuming infinite smoothness and hardness they're all but identical, except a gumball ball race tonearm has 10-20 times more of them and steel is way softer than sapphire. There's no comparison the uni is an order of magnitude lower in contact sutface

Plus the way arm mass/gravity interacts with them hugely benefits the unipivot, but not the ball-race, especially in the vertical plane.

 

[sq225917]

It's all compromise though, from the microphones to the speakers...

 

[wylton]

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...he weeds!

That's because the Linn tight spiel, was plain nonsense right from the start. I have told the story here, a few times about the well-meaning dealer who cracked my cartridge in half because he followed that ridiculous advice! If you have worked as an engineer of any description, you get a natural feel for how tight fittings should be and tightening to the point of distortion is just plain wrong! I have two Naim Aro's and a Zeta. The Aro can be ruined if you overtighten any of the screws and even the Zeta, requires only a nip. On the latter, I do the bolts to the arm-board reasonably tight, but the arm-board to plinth, fairly loose. I'm probably as guilty as anyone in overtightening the cartridge screw to an extent, but at least I know when to stop! I bought a couple of Grahams Hi fi mains distribution blocks and one of them had a rattle. When I took off the plug, one of the screws had been tightened so much, that one of the heads had sheared off!

So I'm with Tony here; sensibly tight so it can't move within the limitations of how much force is likely to incur and no more!

 

[Tony L]

It's all compromise though, from the microphones to the speakers...

Absolutely, and I hope it comes across that I’ll I’m doing is posing questions and suggesting people experiment and listen to the results. As ever I only dig-in against absolutist/fundamentalist statements as they just tend to highlight flawed logic in something as diverse, compromised and undefined as vinyl replay! I really don’t want to get drawn into arguments between different schools of arm design, I can see the good/logic in so many radically conflicting approaches. The point of this thread was just to investigate the current trend for cartridge isolation, plus I added-in the ‘Tom Fletcher approach’ to bolt tightness as I feel it is always worth mentioning as in so many cases it results in a very noticeable sonic upgrade for zero expense.

 

[John]

This is from an early 1980’s Linn LP12 setup manual provided to dealers. I’m not seeing here where they say to cause damage to materials.

WHAT WE MEAN BY TIGHT
Since we are dealing with a transducer that has to recover information considerably smaller than a millionth of an inch from phonograph record, it is important that all the fasteners (nuts and screws) in the turntable be very tight. Whenever the instructions call for you to tighten a fastener, we do mean TIGHT, probably tighter than you ever would have imagined. However SANITY MUST PREVAIL in tightening these fasteners. There is no advantage to tightening them past the point where the associated material will deform, since you are then simply stretching or crushing the materials involved and destroying the structure. A good rule of thumb is simply to bring the nut or screw up to where it seems very tight and then turn it about 1/4 turn more (in the case of armboard screws, which are put into wood, 1/8 turn will do.

The 1998 version of the manual changes those fractions to 1/8 and 1/16th respectively.

 

[wylton]

This is from an early Linn LP12 setup manual provided to dealers. I’m not seeing here where they say to cause damage to materials.

Agreed that most dealers misinterpret what Linn meant, but irrespective of that, I can certainly confirm the damage I have personally seen to arms, cartridges and LP12 top-plates and in any case, tighter than you ever would have imagined is still nonsense advice from an engineering point of view.

 

[Tony L]

This is from an early Linn LP12 setup manual provided to dealers. I’m not seeing here where they say to cause damage to materials.

I’ve no idea how it was interpreted in the USA, but here in the UK it is very hard to find Ittoks and similar era arms that have not been damaged, e.g. very obvious dents/crush damage in the lateral bearing tube where it is clamped by the VTA bolt, chewed-up headshells etc. As stated above, this wasn’t done by misinterpretation of a manual, it was often done by dealers who had actually been to Linn for a “training” course! It really annoyed me as if I’m paying absolute top-dollar for something I really don’t want some idiot breaking it before I got it home!

It has made the second hand market a minefield as so much of this generation of kit is very obviously damaged whereas thankfully the real vintage kit where I’ve ended up largely avoided the mauling of that era. I found the Linn forum you mentioned interesting as they have so obvious rejected this “teaching” entirely and are now on the same page as myself, Tom Fletcher etc. Good to see as it will mean far less damaged arm bearings, chewed up headshells, bent speaker baskets etc.

 

[Iain Docherty]

Absolutely, that is certainly my view. Often from out of the audio range and into it,

PS I quickly looked at the ‘Lejonklou’ Linn dealer forum John mentioned (I’d never heard of it) and the torque values they are using are tiny. The sort of values I’ve been discussing (most values a fraction of an Nm), so it looks like Linn themselves have shifted a very long way from what they were advocating back in the ‘80s. As stated I’ve personally seen more than one Linn “trained” dealers apply astonishing levels of torque to things that clearly didn’t need it. Literally allen-key bending forces! I won’t name them, but if they are reading this, yes, I saw you!

This is interesting, not least because the 1990s LP12 set up guide I have in a cupboard somewhere explicitly defines ‘tight’ as tight enough and absolutely not deforming the materials. I wonder if Linn revised this after seeing the same things you describe?

 

[Tony L]

This is interesting, not least because the 1990s LP12 set up guide I have in a cupboard somewhere explicitly defines ‘tight’ as tight enough and absolutely not deforming the materials. I wonder if Linn revised this after seeing the same things you describe?

I strongly suspect that is the case. My guess is they’d have been getting rather too many returns for kit that left the factory fine but was damaged by their dealer network or by customers with a similar lack of mechanical aptitude following ambiguous advice. The bizarre thing is Linn are a proper engineering company, they should have recognised this rhetoric was just bollocks from the off, but they loved their ‘rigid’ marketing patter and sold metal cartridges when most of the competition was plastic, so certainly had an angle. They dug the hole themselves!

It is a shame as I do very much like the LP12, it remains one of my favourite decks, but it is a risky vintage second hand buy these days (especially tonearms) as so many have been so obviously damaged. I’d certainly prefer to take a blind punt on say a much, much older 301/3012 or whatever in a crusty old wooden sideboard as it is exceptionally unlikely anyone has gone nuts with a screwdriver or spanner on that type of deck!

 

[John]

This is interesting, not least because the 1990s LP12 set up guide I have in a cupboard somewhere explicitly defines ‘tight’ as tight enough and absolutely not deforming the materials. I wonder if Linn revised this after seeing the same things you describe?

I posted an early 1980’s Linn setup manual regarding tightness and nowhere does it say to deform materials.

 

[sonddek]

The contact between the ball bearings and the race are probably less than the point contact on a unipivot.

Interesting suggestion. How does that work? Most ballraces contain more than three balls. The pressure to bring them all (~12-24 in a typical arm) into contact must introduce a small amount of friction and potential for rattle, mustn't it?

 

[sonddek]

Not sure I agree as far as speakers are concerned, at least for some kinds of floors. Why would you want couple a speaker into a wooden floor which will radiate sound, and through which sound will travel faster than air? Speaker designer has done a lot of work making the speaker radiate sound; why mess it up by connecting your floorboards? The sort of stands Northward are offering for (typically) ATCs are well coupled to the floor for stability, but then decoupled from the speaker above about 8Hz. Highly damped fore and aft and against rocking.

Yes, I agree. I did say "ideal". Once you start coupling creaky wooden floors, like the one in my listening room, all bets are off. I suppose my idea of an ideal base for a speaker is an infinitely stiff non-reflective infinitely massive ground to which speakers could be bolted with shipyard bolts.

The problem is that the real world problem is so complex and so varied that it would be easier to fix the room than to design the kit to compensate for it, so kit design comes back to compromises towards an ideal - or an average model, take your pick.

 

[Iain Docherty]

I posted an early 1980’s Linn setup manual regarding tightness and nowhere does it say to deform materials.

Er... I was hardly suggesting that an earlier version would suggest anything of the sort, rather that they might have clarified the text after they’d seen stuff broken by over enthusiasm...

 

[Robert]

Such a complex subject and my preference for very tight v just tight enough varies depending on the situation.

I think we also need to differentiate between rigid and inert.

If I'm mounting a cartridge or adjusting an arm using bolts (where appropriate) them I'm in the just tight enough camp.

However if I'm using a conventional box 'speaker on a stand, I still drill and fit bolts into the floor and sit the the stand into the bolt heads. If the 'speaker calls for near wall mounting then I'll take a cardboard tube, cut just slightly wider than the gap between the back of the enclosure and wall, and press it between the two. Takes up any excess 'sway' and ensures no discernible movement on the enclosure. Why? - better dynamics, especially in the bass.
Conversely, with my Quad ESLs I leave these to flap in the breeze on wheels. They sound better that way. Rigidly mounting Quads amplifies the drum skin diaphragm resonance at around 90Hz - more mud and thickness to the sound.

Tonearms - well that depends because there are many ways to bake that particular cake.
Rega like to use a one piece casting with zero joins.The result is a single high Q pipe resonance in the mid band but otherwise a very clean resonance behaviour.
Others (most others in fact) use various different materials with joins, with or without additional damping. These tend to avoid the large high Q peak and trade this for a multitude of lower Q resonances. Who's right? - they both are, because each delivers a different result and listener preference will vary.

On the question of 'Linn tight' we need to remember the context.

This came about at the time it was deemed acceptable to put a super low budged cartridge onto a high end turntable as the best financial allocation where funds were limited.
The super budget cartridges of the day pre-dated modern Pocan type glass loaded polymers. They were nearly all fairly soft plastic.
Tightening the bolts on a 'soft' body cartridge such as the old Linn Basik or AT95 to just before breaking point does indeed change the sound, in a way thought desirable at the time. Bass gets tighter, mids get firmer, leading edge transients have more jump factor. This is to be expected as you are compressing a soft material against the metal headshell - invariably an Ittok in those days. Of course to this we add gluing the stylus assembly to the body..... and it all made some sense in the context of the old Linn/Naim system sound.
In that context, 'Linn tight' could get you a better sound (to some ears). The problem is that some dealers, and therefore some users applied this as a universal rule, sometimes with hardware damaging results and often where completely inappropriate.

 

[sq225917]

Interesting suggestion. How does that work? Most ballraces contain more than three balls. The pressure to bring them all (~12-24 in a typical arm) into contact must introduce a small amount of friction and potential for rattle, mustn't it?

Surely the pressure to bring them all into contact eliminates the rattle. The issue is that we want them loose enough to move freely, and that exists somewhere before they are all in equal contact. Tolerances eh.

Better to use a smarter design, as I know you agree

 

[pocketkitchen]

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