What defines a good tonearm

Dear Manitunc, To respond to the closest thing to an answerable question that you have posed, with a unipivot there are issues related to not only adjusting azimuth but also maintaining a constant azimuth across the surface of an LP. The Graham and Talea unipivots have addressed this issue, but it is an issue nevertheless. With a unipivot one also has the question of the stability of the bearing. Excess vibrations disseminated from the cartridge could cause the arm wand to rattle, causing bearing "chatter". Many unipivots use some form of damping to eliminate or ameliorate this phenomenon. On the other hand, with a fixed bearing tonearm, there are issues related to bearing friction, maintaining constant friction over time, etc. Like someone else said, I have become convinced that execution of the design, not the nature of the design, is the major determinant of the performance of the tonearm. But this is pretty obvious, so I am not sure what you want to talk about in this thread.

i'm convinced that of pivoted arms, only a unipivot has the potential to work ideally. that's because anything not a unipivot will always be fighting itself to travel the groove correctly.

as always, reaching a theoretical potential is challenging, and a gimbaled arm might be enough better executed to surpass a less than optimal unipivot with more theoretical upside.

after observing the development process of the unipivot Talea 1 and 2 in the company of the Rockport linear tracker, and the Reed, among other gimbaled arms....there is absolutely no doubt that unipivot will rule the roost as time goes by....if not already.

all the issues of any cartridge instability in a unipivot will be overcome completely.

as far as defining a good tonearm, it's simple.

a good tonearm is one where you don't hear any tonearm effects, just music. all the tonearm distortion is gone.

lewm and Mikelavigne

Thanks, finally a response that answers my question. I do believe that a unipivot has the most potential, and now that the azimuth issues are being addressed, I expect they will only get better. It seems to be an elegant, simple solution to most of the issues related to a tonearm pivot. It seems the used of magnets to control azimuth is smart one. Doesnt the Schroeder do that? I also like the idea of the ball bearing pyrimad unipivot that I saw once, but cant remember if it was a helius or benech design.

So, thanks for the responses.

Well, in Tonearm Geometry two Problems have to be solved, the complicated ones and the simple ones.. the complicated ones for example Mass in correlation to Cartridge Compliance, standing waves in the Arm and what to do to avoid them,
The Bearing, Damping, skating compensation, the used wire inside, soldering....but nobody talks about the "simple" Problems like Geometry (the right Geometry!), the interaction from that in combination to tracking distortions...the modern Audiophile thinks, when he has the money to buy a tonearm he automatically gets a perfect Product..well, this is probably the mistake of his audiophile Life. Most today is copied from something, made cheap, sometimes wrong but always served with a high price and a nice finish. Arch Angle is for most "Designers" much too complicated, a top bearing much to expensive and "dynamically balanced Design" is in general a big question mark...but it is important enough that minimizing Tracking Errors is mainly based on that.
The "secret" is in reality no secret, B. Bauer and Dr. Seagrave analyzed the influence between Arm Geometry and resulting distortion of it in 1941, it is valid until today.
Another important view is, for what "Nulls" is the Arm calculated? Close to the last track, far away from it, or even close to the last grooves in the last track? There also also huge differences which shows the user that his modern Arm works great with reissues or records after 1990...but get problems when listening to old Mercury Living Presence LP's. Some Arms simply can't be adjusted properly, but the User will never discover it (the only judgement he can or will do is based on "when I like what I hear then it is good") Doing right geometry is same from costs than doing wrong but when the knowledge is simply not existing what can we expect? The Diamond touches both side walls from the groove, when there is something not absolutely precise, you get a time shifting in the channel reproduction, result is, the details are smearing. you hear that not with a female singer in the middle, but you can hear that easily with older classical records which have huge dynamic swings in parts of a second. And you can't correct it with Azimuth adjustments or similar, the error is in the geometry. This is the reason why some Arms sail through everything and some not.
Some Arms are calculated that they only work with cartridges which have a cantilever length based on that Design, some Arms have nothing, they have a so called "Do-whatever-you-want-Geometry" and all have their Fangroups.
Another interesting chapter is the development from vibration removal and what the result of that is...lot of knowledge is gone (real knowledge, not blabbering), today we have wood tubes which can be bought for $65 in music shops and the drill for it is another 15,--. Cocobolo, Cherry or whatever, nice polish, touched from a Music "enthusiast", kissed before sending it...For some this is good enough. The grail.
For some. Not all.

But even when done all right, do we hear it?
A good question, after 15 years I think, hardly or no. The real money or brain from the Designer is in the reproduction of high frequencies (the ultra silent signals which can open another window in the sonic puzzle). Most Phonostages can't do that anyway (they need a damping to avoid pain in the ears of the listner), most Turntables are not good enough from isolation and most Speakers go into clipping with higher frequencies based on mediocre chassis. This is one reason why average units become a rating to be a Standard. Even when you compare it, it is possible you will never detect it. It is like a bottleneck. This shifting of overall balance (idler fans call it PRaT) is in reality a loss, which is compensated in a different frequency areas (Bass for example). And that is what we have today. The compensation from something "weak" with this or that. At the end of day you can roll a dice, too.

Dear Mike,
You wrote, "anything not a unipivot will always be fighting itself to travel the groove correctly". I don't get that. Can you elaborate? IMO, the "issues" facing unipivot design are precisely those related to the possibility that the bearing allows movement in all possible planes. In a "perfect" pivoted tonearm, if one existed, some of this movement has to be completely prevented, e.g., you don't want the cartridge to "roll" on its axis with respect to azimuth as it traverses the LP. Yet this is precisely what happens with poorly designed and even some highly regarded unipivots. (I don't quite know how to classify the WT tonearms or the Schroeder, but I think of them as a variant of the unipivot. The WT tonearms do exhibit this instability of azimuth. Never saw a Schroeder in action.) Restricting tonearm movement to two planes, vertical and horizontal, is much more easily done with a fixed-bearing tonearm, not to say that is the only path to Nirvana.

Dear Syntax, In fairness to those of us who do like an idler turntable now and then and who also dislike the term "PRaT", I think the term was coined by Ivor Tifenbrun (sp?) with respect to the Linn LP12, which of course is a belt-drive.