Eminent Technology ET-2 Tonearm Owners

Chris.
Thanks for the offer but I must respectifully decline. I am just dialing in my Shelter and newly renovated enlarged room. More distractions, while delightful, are unfortunately just too much for now.
re my building a new arm. The design would allow for bolting to a flat surface with three screws. Simalar to the ET. It has fully adjustable horizontal mass independant of the counterweight. I am struggling with the wand design at present, which is a little radical. While I can visualise it, I'm not sure I can build it. The whole project may founder on this. If I am to build a new arm, I want to be pretty sure it will be a step up from the present version.

Dover, what did you do, loose your ET2 in a drunken poker game or something?

Chris/Richard

As per my earlier post, both an oil trough and a magnet impose a resistance to lateral movement as seen by the cantilever. They behave much like weight in the lateral plane. I have simply used weight alone.

This is incorrect. This is like comparing apples, oranges and pears.
Magnetic dampening will vary with the speed of horizontal motion whereas the added mass approach is simply increasing static inertia considerably. The resultant behavior from an additional horizontal force will be quite different. Same for fluid dampening.
In terms of sound - with magnetic dampening I have gotten increased cartridge output, which indicates that the cartridge is losing less energy due to micro vibrations being damped. By contrast with all fluid dampening I hear a loss of speed, focus and detail. Dynavector also concur with this view in their discussion of their tonearm design. Despite the high horizontal mass they use eddy current dampening to reduce micro vibrations.

In my view the ET2 is the best arm I've used. I changed to a Naim Aro due to problems with a sprung floor and growing tired of pumps, tanks and airhoses running through the house. The ET2 is out on loan, but at some stage it will come back. In engineering terms a unipivot is the most rigid bearing you can get. I chose the Aro because compared to the Graham of the day it had no arm tube dampening, the Graham arm tube was full of crap, and the bearing was the correct way up for energy dissipation to ground ( the Graham had what I call an upside down bearing, point up ). The sound of the Naim Aro is quick, lucid through the mids, excellent soundstage and very musical. The downside is that I believe it has a very narrow operating window in terms of cartridge compliance and mass. The Dynavector Nova 13D sounds excellent as does a Denon 103D. The Koetsu Black sounds awful, unstable in the bottom end. I recently purchased an FR64S to try with my Ikeda Kiwame - this arm is one of the best pivoted arms I have used and due to the detachable headshell I am currently running this so that I can play around with all my cartirdges - Ikeda Kiwame, Dynavector Nova 13D ( freshly rebuilt from the ground up by Dynavector Japan ), Koetsu Black and Denon 103D.
No pivoted arm in my experience can match the transparency and presentation of the soundstage as well as the ET2 though. Furthermore as you will be aware, there is plenty of bottom end depth and speed if set up properly, despite reports to the contrary.

Dover, can you clarify a few points concerning the effective horizontal mass of ET? The manual states that it is 25-35gms. Is this the mass of the wand plus manifold tube, which is then increased by addition of up to 40gms in counterweights?

I understand that the mass of hanging decoupled counterweights behaves differently than fixed counterweights. It would be interesting to have the math on this horizontal pendulum effect. In any case, while the design may lower horizontal inertia to an extent, it will also contribute to horizontal inertia to an extent. I would imagine that the effective horizontal mass of the entire moving system is quite a bit higher than 35gm.

In the course of developing the predecessor of the Trans-Fi tonearm, Poul Ladegaard experimented with a pendulum counterweight. For whatever reason that feature was abandoned.

BTW, with a custom lightened CF slider and wand the horizontal mass of my Terminator totals 35gm. This includes custom front and rear wand counterweights designed to vary the wand's vertical effective mass. On my full-range system with a sub to 18Hz, the lighter horizontal assembly sounds better than the heavy one. Also, variations in vertical effective mass are more impactful than relatively large variations in horizontal mass.

Lots of variables.

Dover.
Magnetic dampening will vary with the speed of horizontal motion..... so does pure mass. The formula F=Ma you quoted in another thread confirms this. Try shaking say a 1kg weight backwards and forwards at 0.55 hz (record hole centering error) and try again at 20 hz, (music). Much more force is required at the higher frequency. If this weren't the case, the R&D dollars speaker driver manufacturers spend on reducing the mass of the moving parts would be for nought. As I said earlier all three dampening methods increase in resistance with rising frequency of excitation.
That said, I agree with you, I do not like the effect of the oil trough.
To be clear, I do like, mostly, what magnetic dampening does. Further it is elegant and kinda cool, but I hear a slight negative which does not exist with the mass approach. As I said, I think that it is caused by induced currents circulating the spindle. Do you really want these currents anywhere near your delicate feed from the cartridge? I would be using mag dampening today if not for this slight negative.
Mag dampening increases cartridge output, yes agree, same holds for mass. My take on this is perhaps different to you. While is reduces micro vibrations which is a good thing, I think that the higher output is because the cartridge has more lateral resistance to work against because it cannot move the arm laterally as much. And move due to the cantilever tracing the groove it must, F=Ma again. More cantilever lateral movement equals more output.

Yes the Dynavector is an arm design that I have studied because it is unusual in using mass and magnetic dampening. But currents near the cartridge output?

Look, I don't actually care if people agree with me on this mass thing. I said earlier that it was contentious. Anyone with a full range system down to the 20s, might want to try it. They could well be surprised at what information is lurking in the grooves.

Dgarretson
Dover, can you clarify a few points concerning the effective horizontal mass of ET? The manual states that it is 25-35gms. Is this the mass of the wand plus manifold tube, which is then increased by addition of up to 40gms in counterweights?

Hi Dave
Page 5 of manual – spindle weight (14 grams) tonearm tube weight (11 gms) plus the counterweights. To give you a reference point I am using one large and one small counterweight with the 420 str. That should be 20 gms.

Page 9
‘By decoupling the counterweights horizontally but not vertically, the mass of the counterweight is not seen by the cartridge above a certain frequency and is lowered. This allows use of heavier (more rigid) components in tonearm design with increasing effective mass. Decoupling mechanism is damped at a 2 – 5hz.”

Maybe Dover, Richard or others can add more regarding the horizontal inertia.

"lots of variables"

YUP :^)

Cheers