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?
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?