What defines a good tonearm

Dear Mike: +++++ " it is the micro and nano wiggling following the groove unimpeded that gives it the advantage over a fixed/gimbaled bearing pivoted arm which on the micro and nano level cannot follow the groove as well. " +++++

IMHO the one that " rides " the recording grooves are the cartridge not the tonearm.
The main purpose of a tonearm ( even if you see it as " ridiculous ". ) is to hold the cartridge because the cartridge alone can't play.

What next?, that the cartridge could ride-free. Do you think that a bearing friction as low as 4mcg. ( like in the Technics EPA-100MK2 ) permit that ride-free condition?, IMHO certainly yes.
Which advantage has any unipivot against a fixed bearing tonearm like that one ? , IMHO none other than disadvantages: you speak of " the micro and nano wiggling ... " and is that micro/nano work the one that unipivots IMHO not solve yet.
You siad ( or Lewm. ) that the azymuth subject and unipivot rattle at bearing is solved and yes a priori is solved because many of us can't detect distortions that came from there. IMHO these to subjects ( azymuth changes and rattle at the pivot. ) exist there and were " controled " at some level but does not disappear and IMHO still have its own influence ( at that micro/nano level. ) on the cartridge/tonearm performance.

These two issues ( in a well fixed bearing tonearm design. ) just does not exist.

Now, IMHO things are a little more complex that only unipivot against fixed tonearm bearing designs. Let me put you some examples:

everyone knows the Telarc 1812 recording ( that I use through my whole test process. ) that not only has a high velocity recording levels but that those recorded HVL were mainly at the inner grooves part of the LP.
I own unipivots and fixed bearing tonearms. Well the B&O MMC2 cartridge mounted on the Grace G-945 ( an unipivot and removable headshell design ) with a 15grs. headshell " pass " cleanly the 1812 recording.
The Audio Technica AT-20ss mounted in the AT-1503MK3 ( a fixed and removable headshell design. ) pass the 1812 test with applomb too.

But, if we take the Colibrí on the Grace one or the XV-1 on the AT one: no one pass the 1812 tests .

These examples tell me that we are on the cartridge " hands ", it is the cartridge the one that " stay " or not in the groove and not the tonearm ( of course that the tonearm is important in this and other regards but it is only an " slave " that works for what the cartridge commands. ).

I don't have a Talea on hand or other today unipivot tonearm design but for my whole experiences and in deep tests about I can tell you for sure that with some cartridges one or the other tonearm will pass that test and with others just can't.

Now, IMHO other than those two subjects that I touched at the begin of this post other issue is that in some way or the other is more easy to design/handle on production an unipivot than a fixed bearing one.

Anyway, as Lewm and Stanwal pointed out: a good design with the right execution ( either design. ) works fine but I prefer a dead steady tonearm design that has not fight against its inherent unstabilities that cause tiny distortions ( normally is better to go " along " the gravity's forces, especially when what is happening at stylus tip and groove level (micro/nano) is so complex and full of " fierce " tracking forces and even temperature. ) but this is only my opinion and as you and other opinions the preferences are different.

Yes Nandric, our tonearm design is not an unipivot one.

Regards and enjoy the music,
Raul.

But it is the stylus tip that follows the groove, not the tonearm. If the pivot is not fixed, then energy transmitted to the stylus tip by the undulations of the groove wall, which is "music", can be lost via "wiggling". Ideally, the arm wand should be fixed in space at its distal end, IMO. Anyway, the point is moot where the very best unipivots are concerned, like the Talea, which blew me away at a local friend's house.

Mikelavigne: "the very best arms i have heard are the Durand Talea 1 and Talea 2 in my system, in other systems, and at shows. i would also add the Continuum Cobra to these 2."

Not to be nitpicking but I just want to point out the Cobra is not really a traditional unipivot because it has a secondary pivot/ball bearing, a sapphire "swash plate" that supports the second spike, much like a training wheel on a kiddie bike. Overall, it has TWO contact points, unlike a traditional UNI-pivot design. The Talea, from my own understanding, does not have a secondary bearing. The Cobra has no azimuth rocking at all. It belongs to a genre that includes tonearm like the Basis Vector, Continuum Copperhead, Graham Phantom, Nottingham Space arm, Holborne, SPJ, and perhaps precious few others. The Graham's secondary bearing is magnetically supported so it's compliant system which is a subgenre within a genre. If you think about it, this group of tonearms are closer in concept to DUAL pivot design like some knife edge bearing arms like old SME and SAEC, or dual spike arms like higher models from Origin Live--essentially two points sitting on a horizontal ball bearing. The Cobra and others are really a hybrid between pure uni-pivot and dual-pivot. A 1.5 pivot?? :)

Oh, the Simon Yorke tonearm uses a teflon sleeve over the bearing post acting as the secondary bearing but does not even use a ball bearing. Very unique and brilliantly simple.

It's debated among designers whether having some compliance or "wiggle" room in azimuth motion is a good thing. Basis' Conti argues that's not a good thing, hence his Vector design. But a rigid coupling is adding and extra contact point is not a good thing to Bob Graham. Which one is better is up to the user to decide but I sure enjoy the choices we can make. Personally, it's fun for me to think about these things and I have dog in this fight. Tonearm theories are so fun! I hope over time we will have enough data from users in the future to describe these tonearms' sonic traits relating to their designs.

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Dear Hiho: You are right, the majority are dual points. The first two points design I know was the one from Audiocraft 3300/4400 from what born the Graham.

All what " surrounded " a cartridge playback is so imperfect that an unipivot ( true one. ) design can't hyandle. We have to think on the forces around LP off center holes along non flat records along what the stylus tip has to negociate on the grooves. A unipivot design is at mercy of all those imperfections along the tracking tip forces that due to its inherent unstability preclude as a " best " bearing choice. This not means it can't works because we have several examples that said it works but the penalties are additional distortions that a fixed bearing ones does not have because that regards.

The cartridge needs at least in the tonearm: stability, dead stability because it is surrounded for to many unstabilities elsewhere.

What like we at home?, IMHO it depends on what kind and level of distortions we accept, which kind of trade-offs we are willing to accept.
Of course that some way or the other we have to have an objective method/process to be aware of different kind of distortions and different level of those distortions.
Many of us are not aware of those distortions and like what we are hearing with out note that what we are hearing is full of distortions.

As I said I prefer a fixed bearing pivoted tonearm against an unipivot but this is me.

My take is that whatever happen between the stylus tip, grooves and record and recording imperfections the tonearm task is to stay steady and neutral to those " movements " adding nothing that put additional " problems " to the cartridge very hard task.

Lewm, lowering by design thgose unipivots issues does not menas disappeared or that has no influence, its means only that the problems are only a little better under " control " but its influence is always there.

The fixed bearing design is perfect?, certainly not nothing is perfect but is more cartridge's friendly and this fact makes an overall difference everything the same.

Regards and enjoy the music,
Raul.

I meant to say "it's fun for me to think about these things and I DON'T have dog in this fight." I apologize for all the bad spellings and syntax.

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