Eminent Technology ET-2 Tonearm Owners

Chris/Frogman -
Thanks for your feedback and comments. I was beginning tho think that analogue heaven consisted of only me and Bruce on a desert island.

I think the key point Chris as you have alluded to is that even if we assumed the Kuzma was the best arm in the world, adding substantive mass to the ET2 is wrong, it is taking it out of its design parameters. To accommodate the mass one would have to redesign the main air bearing and retune the Q of the total system. These factors are being completely ignored by the other folk.

Chris I note that you are also using the carbon fiber arm tube for high compliance cartridges and yet still finding the optimum is only 2 springs with the Benz. This does suggest to err on the more decoupled side of the ledger for LOMC's as well, the only downsides being possibly a fall off below 30hz.
I would be very surprised if many were getting below 30hz in a domestic environment, and if they were it would be unable to be controlled in that environment. To put it another way a roll off below 30hz I would see as an advantage in most domestic environments where room bass response is usually quite uneven and unpredictable.

Further to the above post for those interested the weights of the arm options excluding the wire are: 13g ( Al) . 17g (Cf) & 19g for the heavy magnesium version. So Bruce has designed in only an additional 2-6g for MC's.

03-13-13: Ct0517
The Rockport and Kuzma tubing makes me think of my past experiences with my VPI JMW 12 tonearm. That tonearm’s wires are used as its antiskating method. Their positioning pushes the tonearm back toward the outside.

Could the tubing being in a loop at the centre of the Rockport and Kuzma arm, be acting as a type of dampener for the arms motion in both directions ?

03-18-13 John47
Mr Kuzma replies to MF

[quote]"A question of damping..."
........ There is, in fact, a level of effective damping on the Air Line tonearm. The cantilever suspension, and the air supply tube add damping. Our choice was for either too little or adequate damping; we chose the latter.

John47 - Thanks for confirming my assumptions with the Kuzma.

Dover - My ET 2.5 has the CF armtube and was the one I referenced in my post with the Benz Micro. So many variables here. Plus the specs I listed are for the stock cartridge – it is now a Ruby cantilever SS retip. I have no idea if the specs were changed when it got retipped. Does anyone know what a Ruby cantilever does over the stock Benz Micro one ? The cartridge came with the VPI TNT I bought years ago, and it needed a retip when I purchased it so I never heard it in stock form.

Richard – the triple leaf spring is tight but not 100% tight. It has a tiny bit of flex in it but you need to force it a little. If you hold it by the I Beam and shake it - it doesn't move. Still it is not as stiff as if you stuffed two toothpicks on either side.

Cheers

Re quality factor, Q. ... under, critically or overdamped systems, as they relate to the ET2. My running the arm at 12 psi is no accident. I addressed the Q factor of my arm years ago. And the bearing has no issues at all carrying the extra weight, even at this pressure.

I don't have any proof of this, it is just a recent thought. While higher or lower weight is obviously a factor, I think that the one leaf spring, two leaf spring plus number of weights thing, has probably a whole different set of cause and effect issues. So with reference to a rigid or sprung counterweight beam, it is probably an all or nothing event. In other words because we have the "potential" interaction of the swing frequency of the beam and the resonant frequency of the arm assembly, depending on the number of leaves and the number of lead weights used. It could be that tuning here with springs and weights (and their position) is at least partly to do with sorting this possible frequency interaction rather than just the weight or stiffness employed. Others may have already thought of this but, it is just an idea to put out there for comment.

1986, June as I recall, my first ET.

In '78 whilst studying Engineering at University I learnt a fundamental law of physics.

Q : How do you titillate an ocelot.

A : You oscillate it's tit a lot.

We didn't have Wikipedia in those days.