I have always considered effective mass a wishy washy term anyway, not sure its used in the same way outside of tone arms. Always seen it a little pointless trying to work it out, much easier to stick on a test record and see where the arm has a fit.
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Yep. Essentially impossible to work out, easiest way is to measure compliance and resonance, then back calculate.
How much would effective mass change for the cm or so that the cartridge can slide back and forth in the headshell?
Somewhere between a cunt hair and a pube.
It’s worth trying to understand why its preferable to have a heavier counterweight closer to the pivot.
CNC yourself a tonearm, then you’ll have a perfect model where you could actually work it out. How’s your integration?
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And also why it’s not always in practice. (While I’d agree that theory says it’s preferable, I’ve heard it sound worse, go figure).
Assuming the arm was equally stiff/dead then it wouldn’t matter.
Since they wouldn’t be, which one sounds best is probably down to preference, people love wibbly wobbly arms with lots of wobbly bits (triplanar)
Surely it depends as much on the cartridge. Reducing the effective mass of the arm (by putting a larger weight nearer the pivot) will raise the resonant frequency of the sprung part to a point where it might become excited by LF on the record.
Wait, what? Surely the effective mass will be the same, the benefit of heavier counterweights comes in lower resonances?
Too many variables and depends how close you can get it to the pivot, but you could lower the effective mass by having a short counter weight mount and heavy weight, vs a long one and a lighter one.
Oh I expect so. Take it for what it is, an anecdote with a sample size of 1, but it was definitely better with smaller counterweight, further out. (For the record, it was an Io on an AN arm)
I suspect the low compliance of the Io maybe suited the higher effective mass?
Yeah, that sound plausible.
And also the Io, from the required loading, presumably has less mechanical damping and relies on electrical damping more than others, so all bets are off.
Sorry, I’m not having this. Either I’m missing something or you’re talking bollocks!
If you replace one counterweight with a heavier one closer to the pivot, the effective mass stays exactly the same, doesn’t it?
@edd9000 is talking about reducing the stub on which the counterweight is mounted, which would help, and I understand that, bit you’re just talking about a straight weight swap, aren’t you?
Since its based on the square of the distance, its possible.
The static balance is the same, Ie VTF, but effective mass can change.
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Ooh so it is, makes perfect sense now!
Effective mass INCLUDES the influence of the counterweight. It is the resistance of the whole moving parts to motion, and the resistance to the moving parts being brought to a stop once in motion. It is also known as inertia
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All you need is a Denon DL103 and a Linn LV/V and you are sorted.