What defines a good tonearm

And sheep were nervous?

Stanwal,
And I guess thats my point. I mean, there are DIY unipivot arms on the web using knitting needles with material costs under $5.00 that are being touted as being more than acceptable, so how much more does it cost to make a great unipivot that is priced at $5,000.00. I know they are beautiful, and the workmanship is superb, and they have adjustability and all that, but if unipivot is the answer, why bother with the difficulty of building a fixed bearing design. Or is there some deficiency in unipivots that the fixed bearing is trying to fix.

Stanwal,
Don't misunderstand me, I think the ingenuity and craftsmanship that goes into something like a triplanar or graham or schroeder or any of the other high end arms is well worth the money spent. Much like sophisticated medical or lab equipment, these low volume works of machine art are expensive to create and duplicate. This isnt stamping a shape out of a piece of tin, but real machineing of different metals pieced together to form a working product.
My question is more why is there two basic lines of thought on how to make a pivoted tonearm. Either unipivot or captured bearing and what is the inherent deficiency in each that the other is trying to fix.
My assumption is that a unipivot is more free to move in all directions, and is therefore more likely to track the groove accurately. I also assume that a captured bearing is less likely to allow a cartridge to chatter or bounce around outside where it is supposed to be. And then we have the Townshend silicone trough to damp all this motion, which does seem to work from my experience, although I havent tried it with a unipivot.
Is it your opinion that either of the two pivoting tonearm types is the right answer, and that the other type, while it can be made to sound great, has an inherent impediment to perfection, if that was achievable.

Stanwal,
That would also be Plato's ideal that we could all just sit around and have all this equipment available to audition and make our own decision. We dont. So another option is just to keep buying $4000 tonearms until we find one we like, but we will never know until we try them all, and then something new will come along. This thread was an attempt to narrow that focus down.
I am perfectly happy with the SME 345 I use now, and my system gives me the best sound I have ever heard. But I have to assume that it isnt the best sound available or even the best available for the amount of my investment. But since I am happy with the rest of my system, I was looking to upgrade my tonearm/cartridge starting with the tonearm.
And my premise is based on no two things ever being equal, so one must, by definition, be better than the other. Now, what is "better" is another question, but certainly there must be certain design parameters that are attempted for all tonearms, and each design accomplishes those goals differently than the other, with each having tradeoffs. My question is simply, which one comes closest to the ideal, mechanical and physical goal and why?

Sorry Stanwal. I dont buy your argument. So I guess we can agree to disagree

I am not asking for what is the "best" tonearm, as that is a much too subjective question, as the responses in any thread you look at on this forum would reveal. I simply believe that there are certain goals that all tonearm designers are trying to achieve, and since they are using different means to achieve those goals, they are likely to have different degrees of success. And certain of those common goals might be more difficult to achieve with certain design choices than others.
Any designer knows that when they chose a certain design theory, they are accepting that they have to deal with the inherent weaknesses in that theory and their ultimate success depends on how well they deal with those inherent weaknesses.

My original question was intended to be limited to pivoted arms, not parallel tracking arms as those design limitations are generally much different than pivoted designs, as Acoustat6 points out. I have an ET2 that I can use if I want to go that route.
Again, my original post was asking if there was some inherent benefit to a fixed pivot design that makes it worth the perceived extra effort required to design and construct them. It seems most of the more recent high end tonearms are unipivots or some variation thereof.

Audiofeil,
If the Titan generates a lot of energy, would it not be a good candidate for something like the Townshend Rock silicone trough headshell damping system? My use of that trough with other cartridges seems to result in a much cleaner, smoother sound than without.

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.

So Mikelavigne, what do you think is the current state of the art in unipivot arms and why? And Lewm, the same question to you for fixed pivot arms. And is there an arm in either camp that you think gets it all wrong. These last few posts have been very helpful.

Part of the problem I see, as a hobbyist, is that we never get to hear what can ultimately be achieved by our systems. We only get what we think is the best our systems will provide and whether we like it or not. I guess that's why I do put some faith in reviewers like Fremer just because he has had the opportunity to hear the best, set up by the designer or factory tech, so he has some frame of reference as to what can be achieved, to compare to the item under review. Now of course, he has his biases, just like we all do, but he has a frame of reference that I could never have. So posts like yours are how I learn.