Why are 9 Inch Tonearms standard?

Sorry, you’ve never seen an S arm? All the rage in the 70s and 80s. Still standard on Technics decks and many others. Loads of pics of them on the forum (though outnumbered by straight or C arms 9:1.

Distance from pivot to head is broadly the same as a straight arm with an imaginary dotted line. But the arm makes a gentle S curve to get there. If it was straightened out, it would be longer. Although the head is angled slightly, they hit the same two median points on a 12" disc as a straight arm.

Like many diesign philosophies in hifi, there’s no singke right answer. Proponents of straight will tell you S arms are a nonsense gimick. Proponents of S will tell you straight is fundamentally wrong. A smart customer would decide neither philosophy is a hill worth dying on.

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Or smaller.

I think that isn’t correct, the effective length doesn’t change. The purpose of an S arm is to have the same mass either side of the cartridge which results in more equal distortion on each channel (IIRC). The longer actual length is actually a downside because of the previously mentioned rigidity. Again a compromise like with the length.

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Err, unlikely… in 1973, or thereabouts.

Quote - “That format (16" discs) was standard from approximately 1930 to 1960.”

The two concepts aren’t mutually exclusive. There are a few good articals on tonearm types where the length and distrubited mass are both mentioned together for S arms.

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Of course. Thank you.

How the longer length results in less distortion is because the arc is shallower. The S shape doesn’t change the arc as the stylus will be the same distance from the pivot as with a straight arm of that length.

I’ll try to find those articles you mention. Do you have anything I should search for?

I’ve seen S arms, in fact demoed a 1200G a month or so ago, just not heard the pros and cons between them and straight arms before! This weekend’s homework :slight_smile:

Anothyer detail to note is how the vertical plane bearings are aligned. On some straight arms (such as the the Linn Ittok and Ekos), they are angled to match the angle of the headshell. On others they are not (such as the SME 3009/12).

An S shaped arm may also do the same - or it or may not.

I assume the aim is the keep the cart as close to vertical as possible.

Geometry… :thinking:

Here are a selection of arms, of various geometries, thru the ages (sort of…):

Classic SME 3009:
SME

Grace 707:

Rega R200:
R200

Linn Ittok:
ITTOK LVII

Rga RB300:
rb300

Naim ARO:

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Perhaps on groovywax dot com? I’ve seen 3 articles that associated overall length of the S with the benefits of a longer arm though none mentioned the pivot arc.

I’m prepared to learn new/clarified reasons though.

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Same here. I’ll look for the articles

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An S type arm
Screenshot 2022-08-27 at 08.34.38

PS I would love one of these…

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If they aren’t sold out when our house is done next June, I’m getting the green one.

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I would like it in Lime Green

Screenshot 2022-09-03 at 14.48.22

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Pardon my ignorance, but is that deck actually finished in a khaki green colour, or has the photographer been playing around with the ambient lighting?

Also, is that a Technics tonearm or something else?

It’s definitely a Technics tonearm , dunno about the lighting

best wishes

Ian

3 weeks until I sit down at a dealer to listen to the 1200G, Gyrodec, and OL Aurora… I’m pretty excited. The Technics is winning the heart contest so far X)

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We look forward to hearing your views, I must admit that I would be happy with any of those.

I’ve had Michell and it’s beautifully engineered , the Technics is by all accounts a cracking bit of kit and OL has produced some lovely arms

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There is no objective standard for record players, tonearms come in all kinds of sizes
And shapes and lengths, they don’t even all work on a pivot design…