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Eminent Technology ET-2 Tonearm Owners


Where are you? What mods have you done ?

I have been using these ET2's for over 9 years now.
I am still figuring them out and learning from them. They can be modified in so many ways. Bruce Thigpen laid down the GENIUS behind this tonearm over 20 years ago. Some of you have owned them for over 20 years !

Tell us your secrets.

New owners – what questions do you have ?

We may even be able to coax Bruce to post here. :^)

There are so many modifications that can be done.

Dressing of the wire with this arm is critical to get optimum sonics along with proper counterweight setup.

Let me start it off.

Please tell us what you have found to be the best wire for the ET-2 tonearm ? One that is pliable/doesn’t crink or curl. Whats the best way of dressing it so it doesn’t impact the arm. Through the spindle - Over the manifold - Below manifold ? What have you come up with ?
ct0517
richardkrebs
427 posts
 
Dover.

My calculation of weight delta was based on how much weight the air bearing has to carry. Not the horizontal effective mass. You voiced concern that I had taken it outside its load carrying capability. My calculation is correct since the bearing is supporting the weight of the counterweight, it is designed to take the heavier magnesium wand, the full counterweight complement and heavier cartridges.

Re heavy arms. I assume you are saying that ANY heavy arm, and this includes the Rockports, Walker and Kuzma have serious problems with distortion. Further, by implication, you are saying that the owners of these arms are deaf to these distortions.

We will have to agree to disagree on where we should target the horizontal Fr. In Bruce's paper on the oil trough he talks about the effect of Fr being apparent at 3x its frequency. Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good.
john47
50 posts
 
Bruce Thigpen:

"The ET-2 with the
damping trough will exhibit almost perfect low frequency phase response."

You don't like the ET-2 set up to have near perfect low frequency phase response?

Thats fine, its a free world, but it means you accept/enjoy DISTORTION.

BTW, as you haven't run an ET2 for heading towards two decades, isn't your credibility suspect?
dover
2,318 posts
 
05-15-13: Richardkrebs
Dover.
My calculation of weight delta was based on how much weight the air bearing has to carry. Not the horizontal effective mass. You voiced concern that I had taken it outside its load carrying capability.
Optimum load capacity. You have added 30g of lead to the mass the bearing has to carry. This has 2 negative effects - it pushes to mass to the extreme and one would redesign the bearing if one were knowingly going to operate the arm at a higher mass level. Secondly the added mass will impact the shearing forces involved - the arm is not frictionless and the bearing is not absolutely rigid - these are some of the reasons why users are hearing different results with higher pressures.
As a point on your calculations on FR I led slide the error in your calculations - the bearing has a resonance, the bearing tube has a resonance and the total resonance will be a sum of the resonances inherent in the arm. One really needs to measure the resonances to see whats going on , thats why Bruce does extensive testing. The maths you are using for FR calculations is not the complete story.
05-15-13: Richardkrebs
Re heavy arms. I assume you are saying that ANY heavy arm, and this includes the Rockports, Walker and Kuzma have serious problems with distortion. Further, by implication, you are saying that the owners of these arms are deaf to these distortions.
I think you should use the word preferences, when making judgments on other folk, but certainly they may well be. Some folk like fat bottom ends others prefer speed and musical timing. For me music is about timing and nuance - I can certainly hear the slugging of the sound and loss of musical timing when adding too much horizontal effective mass to the ET2 as others in this thread have also found when they removed the decoupling from the I Beam.
You may also like to read the comparison of the Kuzma to the Walker in the Absolute Sound mag December 2006 where the reviewer articulates the differences - the Kuzma being dark and solid vs the Walker having more of "the "gestalt" of a live concert, more lifelike presence of instruments, their colors, their dynamics, and the space they play in" of the Walker "fuller, more realistic in tonal color, bigger, bloomier, wider, deeper, more layered in soundstaging, and a bit more authoritative dynamically".
05-15-13: Richardkrebs
Targeting say the 12 hz you mentioned would mean that it is causing phase and amplitude problems at 36 hz. This is not good.
Depends how big the amplitude problems are. Some of the heavy arms you have mentioned have additional measured resonances at 100hz & 200hz.
In your case you you have reduced the theoretical resonance from 8.08hz to 5.17hz. so yes you have a small residual at 24hz in a standard unmodified arm - but this is outweighed by the amplitude of the resonance being much higher when you added 62g of horizontal effective mass. Furthermore that small secondary resonant peak at 24hz with the standard arm can be dialled down with careful tuning of the counterweight spring. I very much doubt whether many systems are truly flat to 20hz in a real home environment.
In your case you have shifted the secondary resonance from 24hz to 15hz, but have increased the amplitude of the 15hz resonance substantially - probably 6-12db higher in amplitude compared to the smaller resonance at 24hz with the arm as standard.
spock15
8 posts
 
Chaps...I'm not an ET user nor an Aro user, but I do use both a 12" unipivot + an air bearing linear tracker, so if I could be permitted to offer a humble opinion, hopefully useful to the topic ;)....

In this game, sometimes we tend to think about what we SHOULD hear, rather than what we DO hear...

In principle, the tolerance gap of a air bearing leads us to think that an air bearing will be therefore compromised sonically - ie. because it will never have solid bearing contact. However I hear no lack of 'leading edges' with a linear tracker. So what is going on?

On the topic of 'leading edges', I think a 'square wave' is an appropriate analogy. The leading edge of square wave (rise time/slope, overshoot control...) is determined primarily by the HF component of the signal/tone. In the same way, the perceived 'leading edges' of sound is poor, if the HF harmonic component of music signal is compromised.

A unipivot typically has excellent HFs, owing to absence of 'bearing rattle'. I also hear excellent HF tone & extension with an air bearing tonearm. Go figure...

The explanation I think is that, at groove modulation frequencies, it is not the rigidity of the bearing that is key, but rather the inertia of the tonearm, as 'seen' by the stylus, that is key. From this perspective, a pivoted tonearm rotates freely, ie. has very low (rotational) friction.... and a linear tracker also has low (linear) friction. Both are similar... but from the viewpoint of the stylus in groove, 'inertia' or Effective Mass (at groove modulation frequencies) must be high - adequately high to reproduce LF signals without resonance/loss of power delivery.

Contributes to the discussion I hope.

(Apologies if this is old ground, I haven't managed to read all 700 pgs ;) )
dover
2,318 posts
 
05-15-13: John47
Bruce Thigpen:
"The ET-2 with the
damping trough will exhibit almost perfect low frequency phase response."
You don't like the ET-2 set up to have near perfect low frequency phase response?
Thats fine, its a free world, but it means you accept/enjoy DISTORTION.
No I dont believe Bruce Thigpen does enjoy distortion. On the contrary Bruce Thigpen has cleverly designed an arm that tracks superbly and can be fine tuned via the adjustable VTA, Azimuth, and decoupled counterweight.
Bruce Thigpen does not add 60g+ of horizontal effective mass and remove the decoupling of the I Beam.
The perfect phase response that Bruce obtains with the damping is achieved by operating the arm within its design parameters. Keeping the horizontal mass as low as possible is part of the design. Adding 30g of lead to the arm and removing the counterweight decoupling will indeed create significant distortion, including an inflated bottom end and phase anomalies, but that is not how Bruce runs the arm.
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