"S" shaped tonearm ?

Professional designers are also beholden to the prevailing design theories and manufacturing methods currently available. Tonearm manufacture can only tolerate a few design types and remain cost-effective and competitive, so designs that don't fit the business model are rejected before they can even get started.

I've been in audio for 40 years and have watched the high end throw one dogma over for another about every decade or two. I remember when horns ruled in the heydey of JBL, Altec, and Klipsch; and then were repudiated in favor of silk domes. For a long time high end dogma dictated that a horn speaker could not be high end. Oops! Along comes Avante Garde of Germany. There was a time when no self-respecting high end speaker design was ported; now most of them are. Most speakers today have to be bi-wire capable, even if there is no benefit to designs with 1st order crossover. If it lacks the features that are in currently style, it won't sell.

Right now in tonearms it's the straight, one-piece armtube, preferably with integral headshell, with a unipivot bearing. A straight, one-piece arm w/integrated headshell is the cheapest to manufacture and may have advantages in rigidity vs. weight. It's also an absolute bit** for mounting a cartridge. Still, current turntable/tonearm dogma dictates that nothing but a belt-drive with straight arm w/unipivot is going to succeed in the marketplace.

The once-ubiquitous dual-gimbal fulcrum has largely given way to the unipivot design. The unipivot bearing is cheap and simple, but has little to no ability to stabilize or control azimuth. A dual-gimbal design allows free movement in the x and y planes while limiting movement in the z plane to bearing play.

And here's an alternate automobile analogy to the 1958 Edsel. Prevailing leading edge engine design dictates an alloy block, double overhead cams, and 4 valves per cylinder. But then there's the Corvette Z06 with a cast iron 2-valve pushrod engine, which at $70K, can beat or stay even with any supercar up to around $250K. And if that isn't enough to push the envelope, the Steve Saleen S7 $400K supercar has a 2-valve pushrod engine as well, yet puts out 550 to 750 HP. The SR-7 racing version has had much success on the competition circuit (e.g., Sebring, Le Mans).

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?

Jrw40:
what is the reason a company ,such as denon for instance to put an "S" shaped tonearm on there table. ive had both straight and S . and while not high end , i currently have the denon dp500m table . ive heard nor seen an advantage to either, though my experience is very much amature audiophile.

Now that this thread has beat tonearm design theory to death without answering your question, I'll make a stab at it.

The two main turntables (that I can think of) that are using an S-shaped arm are the Denon 500M and the Technics SL12x0 variants. I can think of several reasons they might do this.

* We've already established that to use a detachable Universal headshell on a 9" tonearm, there has to be a bend in it for better tracking angle. This means the wand will be a J or S shape.

* In Japan, the home market for these manufacturers, the S-shaped tonearm and universal headshell are both still popular. E.g., Audio Technica still makes a J-shaped tonearm with detachable headshell for $1900. It's at AudioCubes II here. The detachable headshell thing is popular enough over there that ZYX offers a universal headshell at about $550. See it here.

Technics and Denon have probably determined that offering a manual turntable with detachable headshell still has market viability. Being able to use a tonearm design from the '70s on a direct drive transport enables them to maintain a presence in the turntable market, offer higher build quality for a lower purchase price, and avoid R&D expenses on a market that currently can't generate the numbers they require to invest in new R&D.

But some of these "S" Arms have their "Birth" only from Design reasons.

Or marketing reasons. For the last 20 years, a new arm wouldn't be taken seriously unless it has a straight shaft and integrated headshell. But back in the '60s and '70s when high end turntables descended from professional radio gear, it wasn't considered a serious tonearm (and therefore wouldn't find a market) unless it had a detachable universal headshell. And on a 9" arm, that meant the wand had to curve.

One could say that--*all things being equal*--a straight arm with integrated shell has an advantage. But "all things" are seldom equal. The Rega RB300 is a highly regarded tonearm, especially for the money. Its strongest point is probably its straight, tapered tonearm shaft with integrated headshell. But it has other vulnerabilities such as unadjustable VTA, a VTF spring that's prone to resonate according to some users, and iffy azimuth.

Compare it to an old-school S-shaped tonearm such as a Technics EPA-100, and the Technics has advantages in lower bearing friction, a double gimbal design that maintains azimuth alignment better, a titanium wand that cheats conventional rigidity-to-weight expectations, and perhaps most wonderful of all, dial-in damping to accommodate a wider range of effective mass/compliance ratios.

Economy of scale comes into play, too. That's one reason an RB300 can be considered so good at $400. But if a company found the market potential to scale up to make 3 times as many per year, they could afford to make a better tonearm from better materials, closer tolerances, and more features at the same price.

Is the RB300 a better arm *simply* because it has a straight arm and integrated shell? In this case, probably no. Would an EPA-100 be better with a straight wand with integrated shell? Probably. Enough to tell the difference? Who knows?

Then there's the issue that "different" isn't always "better." At a given price point, a straight arm might have better imaging and leading edge transients; another design might have deeper bass or richer timbres. If you're only listening for imaging and treble, you'd conclude that the straight arm is "better." But someone else listening for the body of the tone might prefer a different tonearm for sounding more timbrally accurate.