"S" shaped tonearm ?

The genesis of "S", and for that matter "J", shaped arms is probably buried in the mists of time, though I think that Larryi has a pretty plausable explanation. The only reason that I can see to currently design one of these arms is that it becomes compatible with universal headshells, which are absolutely necessary in the DJ world and pretty convenient in the audiophile world, though as Bill stated, there will be a high sonic price to pay for such convenience. As always, sigh!

I always thought that S shaped arms started disappearing around the time MCs became the rage and that it was discovered that you needed a more rigid arm tube for MCs than with light and compliant MM or moving iron designs, so that extra material to make it stiffer and extra material to keep the S shape just wouldn’t do.

I remember the SME model that was S shaped with a titanium wand and I think it was no slouch teamed with a compatible cart.

I like the way you seem to think that everything made now is better than everything made then. I guess one does fall into that trap when one is a monger.

Pbb, I hope that you are not addressing me with your last comment. I enjoy older technology. For the record, my turntables are 1960 Gray ST-33 with ESL S-2000 tonearm, single speed table, no cueing or anti-skate on the arm, 1969 Thorens TD125AB MKll with TP13A tonearm, 1972 Micro Seiki MR711 with MA202L 10" tonearm, 1982 Logic Tempo E with Datum 2 tonearm. Happy to own both DD and belt drive tables and both "S",and "J" shaped and straight arms. As Bill would point out, all of this stuff is way off of the current pace. I will be buying a Hadcock from him for use with my Grado Signature, when I find a suitable table, and mostly, when I get some remodeling done on my house and have some cash to splash out with.

Marty

Well, here are my guesses - form followed function.

Until sometime in the 50s, most arms were straight. Then, when the importance of offset angle became better known, arm manufacturers designed "S" or "J" arms to achieve this angle. Also, remember at this time it became common to have a removeable headshell, something easier to implement with a S or J arm if offset was to be maintained. Next, in the mid-70s high compliance cartridge designs became more popular, thus requiring low mass arms. It was easy to see a straight arm would have lower mass, all other things being equal, so many lower mass straight arms with offset headshells were introduced. Then by the late 70s/early 80s, MC cartridges became more popular. Being lower in compliance (on average) they required higher mass arms. This time, realizing straight armtubes were easier and cheaper to build, manufacturers continued with straight arm designs but with higher mass, a practice continued to the present.

If you read fellow 'goner Raul, you may see that sometimes straight arms work best, sometimes S or J arm are a better match. Similarly, a fixed headshell should not automatically be assumed to be superior. In reviewing Raul's comments, you'll see that sometimes the surprising arm/cartridge match is the one which works the best.

I think definitely the J and S-shaped arms evolved out of designing 9" arms (as opposed to straight 12" DJ arms) to work with a universal headshell. I remember the SME arm of the early '70s being J-shaped. The Japanese turntables of that era were almost all S-shaped, which looked real "technical" at the time. But even the early generation Linn and Rega TTs had S-shaped tonearms with detachable headshells.

Later, in the quest for improved weight/stiffness ratio, the high end industry scotched the detachable headshell and S-arm for a straight arm and integrated headshell. This was fine and dandy but it also created a couple of new problems: Mounting the cartridge was going to be a lot harder, and a straight cylindrical tube would have a stronger single resonant frequency.

So now, some--but definitely not all--cartridges have built-in threads to make cartridge-mounting easier. Still, this old sight-and-fine-motor-challenged guy wonders how I'd ever successfully mount a cartridge without my beloved detachable universal headshells. And many straight tonearms are now tapered--slightly conical--rather than cylindrical to reduce the resonant frequency. This would increase the mass a bit; I wonder how much mass it adds compared to stretching the tube into an S-shape?

One question I have to ask though, wouldn't an S-shaped arm be stiffer in the horizontal plane? Also, bending the arm cylinder into three dissimilar lengths could help control, reduce, and possibly even cancel resonances.

Then there's the matter of build quality, tolerances, and skill of execution vs. design theory. In theory, an integrated headshell and straight arm has an advantage in rigidity between the pivot and the stylus. But the Technics arm's bearings are finished to a tolerance of .5 micron and a specified bearing friction of < 7mg. Might that not offset some S-arm's other disadvantages?