BLACKMASS
pfm Member
Great, thanks very much. The 90 degree plugs might be a good idea, cheers.
(Well Tempered) Tonearms?
- Thread starter BLACKMASS
- Start date
Great, thanks very much. The 90 degree plugs might be a good idea, cheers.
loheswaran
Member
I’ve been pondering a Wt arm for a DD deck. Are the golf ball arms better than the older arms.
pocketkitchen
Registered User
There’s a good video here:
I used this when setting mine up. Worked a treat. Go slowly and carefully with the silicone!
Maybe not mentioned?
Unless there is some clever design and engineering involved, a longer tonearm will have a significantly higher effective mass, primarily because the headshell is further from the pivot. To get rid of the extra, the wand would have to weigh an awful lot less in the longer version. (All parts of the tonearm will have increased effective mass, but the major increase is with the headshell - see below.)
The reason?
Effective mass is the sum of the effective massees (inertia) of all the individual components of the moving parts of the tonearm - headshell, wand, pivot assembly (which can have an inertia of zero if it is symmetrical about the pivot), CBW stub and CBW - they are all additive, no matter what side of the pivot. Inertia is the mass of that part multiplied by the square of the distance between the pivot and the centre of mass of the part.
A headshell is light, but is a long way from the pivot. The centre of mass of a parallel wand would be half way along its length - roughly half the distance as the headshell centre of mass. Moving from a 9 inch to 12 inch arm, all else being equal, increases the effective mass of the headshell by 144/81 = 1.78 = 78%
Adding damping fluids adds to effective mass due to viscous drag, pivot friction also adds, but is (hopefully) very low. Effective mass (tonearm inertia) is a measure of how stable a tonearm is, how resistant it is to being moved.
Effective mass has implications for interaction with cart' suspension.
Edit - there is a chance that the increased inertia of the headshell could be counteracted by a CBW of increased weight (which would have lower inertia than a lighter one), but you'd need real numbers for everything to work it out. I doubt that it would be possible in the real world, but I would be happy to be proved wrong.
Unless there is some clever design and engineering involved, a longer tonearm will have a significantly higher effective mass, primarily because the headshell is further from the pivot. To get rid of the extra, the wand would have to weigh an awful lot less in the longer version. (All parts of the tonearm will have increased effective mass, but the major increase is with the headshell - see below.)
The reason?
Effective mass is the sum of the effective massees (inertia) of all the individual components of the moving parts of the tonearm - headshell, wand, pivot assembly (which can have an inertia of zero if it is symmetrical about the pivot), CBW stub and CBW - they are all additive, no matter what side of the pivot. Inertia is the mass of that part multiplied by the square of the distance between the pivot and the centre of mass of the part.
A headshell is light, but is a long way from the pivot. The centre of mass of a parallel wand would be half way along its length - roughly half the distance as the headshell centre of mass. Moving from a 9 inch to 12 inch arm, all else being equal, increases the effective mass of the headshell by 144/81 = 1.78 = 78%
Adding damping fluids adds to effective mass due to viscous drag, pivot friction also adds, but is (hopefully) very low. Effective mass (tonearm inertia) is a measure of how stable a tonearm is, how resistant it is to being moved.
Effective mass has implications for interaction with cart' suspension.
Edit - there is a chance that the increased inertia of the headshell could be counteracted by a CBW of increased weight (which would have lower inertia than a lighter one), but you'd need real numbers for everything to work it out. I doubt that it would be possible in the real world, but I would be happy to be proved wrong.
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Dirkster
pfm Member
Agreed.
After a 'back to basics' setup session during a recent lockdown here, it became glaringly obvious to me that 'less is more' when dealing with the silicone damping fluid.
I had previously been led to believe that 1/3 of the ball should be submerged, which I can safely state is nonsense. With the ball barely touching the gloop, the sounds coming out are frighteningly real.
Such a shame it took me so long to work this out!
loheswaran
Member
The guy who makes the £30k SAT arm says 9 inches is better. Max Townshend said to me in a conversation the shorter the better too. So there are clearly two knowledgeable people that prefer 9 inch
RichShortland
pfm Member
I use a DIY Amadeus copy arm using the golfball on my modified Lenco. I’ve just swapped it out for a PTP one with speed controller but haven’t got the arm mounted yet, so can’t comment on that, but it worked great on my old Lenco. It was that good it saw off several other arms including a Roksan Nima.
I bet he says that to all the girls.
