Eminent Technology ET-2 Tonearm Owners

My apologies in advance if this topic has already been covered in the thread. Too many posts to read thru.
Twenty years ago I made a oil damping trough for the then standard ET2, mounted on a Goldmund Studio. Mixed results, which could have been as much to do with opening the window to the performance of the Studio, as anything else. I put it in storage and forgot about it, only to find it again recently when looking for the aluminium goose neck for Chris.
So installed it on the current arm. Nice changes to the blackness of the background. The system is even quieter. As a result, it doesn't seem to extend dynamics upwards but downwards further into the low level detail. A very agreeable effect. Also greater presence and focus. It will be staying.
Is anyone else using an oil trough? If so what are your findings? I see from the ET website, that a very elegant design is offered.
bdpses

Andy Payor and Bruce Thigpen both disagree with adding mass.

Hi Dover,

Regarding the passage you quoted Andy Payor from Michael Fremer’s review on the Rockport 6000, while I have never read that review, but reading MF’s later reviews on the Rockport Sirius III and Kuzma Airline, gave me the impression that those comment were from MF himself rather than AP. Of course, AP might very well agree with that! Can you confirm?

About AP’s disagreement with adding mass, I would like to share some information. In the later, upgraded, models of the Rockport 6000, i.e. the 7000 and the arm on the Sirius III, AP chose to use heavier armtubes. I believe all 3 arms used the same air-bearing, and their armtube clamping systems are of the same (or very similar) total weight, but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

The heavier tapered armtubes (so the heavier moving assembly) on the later arms are said to be there for better bass performance, and minimize resonance. Granted, AP might have added the weight to help (add) more in the vertical, rather than the horizontal, moving mass, for better matching with mid/low compliance cartridges, but added weight he did! That may just be a matter of compromise!

The kong,
I am on a project at the moment and cant get back to the article but I believe it was a direct quote..I can confirm later if you like.
Meanwhile I see in the stereophile review of the Sirius arm: August 2000

The Sirius tonearm tube should be virtually inert, made of a constrained-layer-damped, 8-ply sandwich of carbon fiber and epoxy composite: four layers on each side of the damping material. Inside is a second tapered carbon-fiber tube, the space between the two filled with yet another damping material. The materials, construction, and aerospace pressure-laminating techniques create an armtube said to have the stiffness of steel, yet weighing only half as much as a comparable aluminum tube.

Another single billet of aluminum alloy is machined to make the bearing mount, tonearm clamp, and counterweight assembly. This is a big improvement over the design of the Series 6000 arm: the structure is said to be 20 times stiffer than before, yet no heavier.

This suggests the armtube is more rigid in the later models but lighter.
Fremer also paraphrases Payors comments on the ET as follows:

The air-bearing scheme—comprising a stationary bearing and a moving rail—invented by Eminent Technology's Bruce Thigpen and used on his tonearm as well as on the Maplenoll and Walker Audio turntables, comes closer to being truly "linear" because the bearing can be more highly pressurized. But the rail's large horizontal moving mass creates another set of problems. And a true linear tracker completely eliminates a pivoted arm's inherent tracking error and skating-force vectors.
All of which, to Payor, means that his arm is the best currently available, and the true state of the art.This is extremely important, as low moving mass is critical to the performance of a linear-tracking arm.

The use of English can be deceptive - large, heavy, higher mass. We see that Thigpens "heavy" armtube is only 2 gm higher. Payor may be referring to the physically large area of the arm/bearing tube or he may be referring to the actual mass, but it seems clear to me that he favours minimising the horizontal mass.

Furthermore, if you read the full article you will see that the bearing design and parameters and moving masses involved are mutually dependent as they are on all airbearing tonearms. I dont believe you can convert a Kuzma to a low mass or an ET2 to a high mass arm without redesigning the air bearing.
The resonances of the bearing itself can end up in conflict with the resonances generated by the arm/cartridge compliance.

This is where Richardkrebs continues to get the maths and physics wrong; there are multiple resonances involved, and the multiple resonances can quickly accumulate when overlapping - they are not a single spike at one frequency. This is what is happening with the ET2 when Bruce measures a 6-12db lift in the bass when coupling the counterweight - which effectively doubles the horizontal effective mass.

Richard re: damping trough. Thanks for bringing this up. I have completed my game of musical turntables, so I will revisit the damping trough now. It can get messy when moving an ET2 from one TT to the next with a trough of oil attached !
My main TT is completely changed from the last time I used the fluid so will try it again.

The fluid that Bruce uses in the trough is 8000 centistoke silicone fluid. I ordered some today from him along with the adhesive. Will post impressions later.

Richardkrebs - My apologies in advance if this topic has already been covered in the thread. Too many posts to read thru.

Richard - This thread is unfolding like a book. Very relevant ET2 information was discussed early on and throughout. I encourage a read through. If for no other reason than to understand and gain insight into why some members made the decisions they did.

Cheers

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325551242&openflup&67&4#67

Thekong - In the later, upgraded, models of the Rockport 6000, i.e. the 7000 and the arm on the Sirius III, AP chose to use heavier armtubes. I believe all 3 arms used the same air-bearing, and their armtube clamping systems are of the same (or very similar) total weight, but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

....Granted, AP might have added the weight to help (add) more in the vertical, rather than the horizontal, moving mass, for better matching with mid/low compliance cartridges, but added weight he did! That may just be a matter of compromise!

Thekong - thanks for sharing this info. Are you able play high compliance cartridges on your Rockport arm ? We know the heavier ET2 armtube affects the horizontal mass as well.

but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

I am assuming that this would limit the type of cartridges the Rockport Sirius III tonearm can now play as far as compliance is concerned ?

Cheers