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Adding mass to a tonearm. Best principles?

Rockmeister

pfm Member
My SME M2 9 is quite light at 9.5g mass. It makes it edgy for some cartridges, esp those that are both light and low compliance (I'm thinking of a Lyra Delos which is not a perfect match as is). Ideally I'd like to add 7-10 grammes mass to the arm.

Reading around, the wisdom seems to swing from 'bung on a heavy headshell', to counterweight additions.
I think I can see that anything that causes the counterweight to be placed further back (like a heavy headshell would do) is not an ideal solution, so the added mass needs to be near the bearings...as near as possible. So? Behind the bearing assembly, (but is this in the right place, behind the balance point, to do any good)? Or maybe just in front of the bearing wrapped around the arm tube itself?

I have in mind cutting to size and weight some simple lead sheet (plumbers roofing repair type stuff) which has the obvious advantage of weight with little bulk, and the ability to stay in a shape (and hopefully, in place) once formed...I'll simply bend it around the arm tube.

All thoughts welcome. The present cartridge is also 'just' in the green OK resonance zone, so I'll try the final theory out on it and report back. Currently at 11Hz resonance, I can move it into the magic 'perfect 9Hz' zone by adding 8g.
 
Or you could just insert the arm tube into another tube. That’s what a German Thorens vintage gear seller does to the TP16. I’ve seen it but I can’t remember where.
Another route would be filling the arm tube with lead shots.
 
yes I did think about filler, but it'd not need to shift at all, or your stylus force would be all over the shop, and then there is the wondering about what's going on with those delicate wires inside? :) I think the tube idea would be neater, but would need someone to engineer it. My lead is free. But where to put it?
 
The conventional solution is a sheet of metal under the cartridge. I think the mass is more effective at the cartridge end, hence "effective mass" not just mass per se.
 
The way I understand it, for a mass increase to be 'effective' it need be well out in front (i.e. cartridge/mounting hardware/headshell), as adding any near to the pivot is only altering moment of inertia, not the resonant frequency of the suspended beam.

Another way of looking at the problem is that the back end of the suspended beam is fixed, whereas, the front end is spring suspended.
 
ok, I see, but then a counterweight then set much further back to allow for this extra mass is also not good = heavier counterweight too = more mass = erm?

I'll try a little lead wrapped around the arm tube an inch or so in front of the bearings and start there ;)
 
Confucius say, man whose car has too stiff front shock absorbers will not fix problem by loading more weight in boot.
 
confusedious ask...you mean it's just a matter of bending cantilever on cartridge more?
But the cantilever is still going to only 'see' 2.1g as per now.
 
Confucius say, man whose car has too stiff front shock absorbers will not fix problem by loading more weight in boot.

Oh I see! And he created cartridges with a compliance of 40 in the 70’s.
But why oh why don’t they do it any more?
 
As I understand it the closer the added mass is to the balance point the less "effective" it is.
Mass added at the headshell with balance weight corespondingly more rearwards is
 
I use 3g brass nuts off ebay with SME4 and Koetsu, seems to help the bass. I don't really understand this effective mass malarky, but I've never heard Denon 103 sound so good as it does in Fidelity Research FR64 fx, effective mass @ 20g.

http://rover.ebay.com/rover/1/710-5...0001&campid=5338728743&icep_item=232754662709

I wouldn't use blutac cart/headshell contact, it sticks like the proverbial , veneer ripping strength next to a cantilever !?
 
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Headshell weights.

images
 
High effective mass tonearms just are not that popular these days...sigh. Well I'll experiment and see. Lead cutting commences. Lead and blu tac is attractive isn't it? :)
 
Skimming through replies here, I would suggest that you take some time to read what effective mass of a tonearm actually is.

Just arbitrarily adding mass here and there, wherever takes your fancy, is not at all what it is about.
 


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