Eminent Technology ET-2 Tonearm Owners

Slaw, welcome back to the thread. What you see on the arm wand (magnesium) is a very exotic rubberized cloth material used as a wrap, and sourced from a local supplier, called Lowe's rubberized cloth gaffer's tape :-)

In an attempt to tame my Vandenhul and Shelter MCs' aggressive top end, I wrapped the arm for extra dampening; it worked well. When I began using MM's again, I went back to the original lighter wand which works better with them.

Chris, eliminate the competition, I always say :-) Man, I wasn't even close! Over 2000 ET2's sold; I would never have guessed the number to be that high. I figured 1200 or so by the time the arm was discontinued (before being brought back). When was that article written?

eliminate the competition, I always say :-)

Frogman - remind me never to enter a sports competition against you. I could get hurt.

Well curiosity killed the cat - my intentions were good. I figured put in a decent bid; win that auction for the ET2 reports; scan them and make the info available here.

So as the ebay clock winded down I strategically waited to make my move.
Nothing gets my heart pounding like an ebay bid.
59 seconds left I put in my bid and received the message back - No shipping to Canada !! sigh....

I will ask Bruce about the date - a little later. I am lying low with him for a bit - he has received so many emails from me.

Cheers

Lets look at things again.
I am officially retracting my retraction to Thekong regarding the ET2.5. Here is why.
When I realised my obvious mistake in thinking he was going to place a rigid CW arm on an ET2, when in fact he was proposing to use one on an ET2.5, I looked at the figures for this arm.
On 03/14/13 Chris posted the Horizontal resonant frequencies for the two arms. ET2 5-6hz ET2.5 2-3hz.
I already knew the horiz mass of the ET2, so calculated the mass of the ET2.5 assuming the same cartridge mass and compliance was used for both arms( a reasonable asumption)
Res freq is proportional to the square root of the inverse of the mass. In other words 4x mass = 1/2 res freq. Since the ET2.5 freq range was approx 1/2 the ET2, it implied that the ET2.5 was 4 x heavier, making it over 100 gm. This surprised me but in the absence of any other information, I took it on face value.
From experience it would be problematic if Thekong were to add a rigid weight to this apparently already heavy arm. Later on in the thread, 03/14/13, Chris published the actual weight of the ET2.5 being only 8gms heavier than the ET2. This means that ET did not use the same cart parameters when giving Chris the original info. Thekong, your call obviously but if I were you I would try a fixed CW arm provided it is really rigid.

Re my question re interaction between the two spring rates, cart and CW. I raised this question, not because I had suddenly "understood" how the ET2 worked but because the idea that having two springs driving the same structure could actually have a down side. I started thinking about this when Dover commented on the superior transient performance of his unipivot. The idea further coalessed when the tests were done with loosening the CW arm bolts. This would change the Q and possibly the res frequency of the CW assembly. Potentially reducing any interaction between the two springs, but not eliminating it.
When I fixed the CW and added further mass and used a low compliance cart, there was an unexplained positive side effect. Focus and sharpness improved. Transients were better. It was some years ago when I made this change and while liking the improvement, I didn't put too much thought into 'why'. While I did not post these positive results. My question to the fellow posters was " could the interaction between these two springs be a problem." I don't know, but it is a valid question and the graph I posted suggests that they do "talk" to eachother. My thinking was that there may be a link between the transient improvements I acheived and the use of a swinging CW.

When I first purchased the ET2, I set it up as per the manual, to the point of obsession. As with all of my gear, I wanted to extract every tiny bit of performance. In standard from, it was best as per manual, with the slight adjustment of swinging the Ibeam down as Chris has posted.
Years later I started to experiment. The result is what I have now. It is just my opinion, no more or less valid than anyone else, but I believe that it is significantly better than a standard ET2, when using low compliance carts.

We can debate this from first principles all we like, but the proof of the pudding is in the hearing. What does it sound like, how does it perform? This is evaluated with our ears.

I will not be degrading my arm by converting it back to standard form.

Richardkrebs.

If you prefer the sound of your ET2 loaded with lead and decoupled counterweight removed thats fine.

A couple of technical points though.

Paragraphs 1-3 : You miss the point here. Your quasi-mathematical arguments on resonant frequency are meaningless because the arm is more complex than what you appear to comprehend. You continually factor only one resonant frequency into your arguments to attempt to justify your opinion. The ET2 as designed has a multitude of resonances, which you appear to be oblivious to and ignore in your calculations. I use the word calculations loosely here, as I suspect your numbers are mostly guesswork.
You have ignored
horizontal/vertical resonance of the cartridge
horizontal resonance of the sprung counterweight
the horizontal/vertical resonance of the air bearing
natural resonances of the bearing tube/rigid arm wand
natural resonance of the counterweight assembly.

Count them up. This is the fundamental flaw in your postulations.
The arm is a precision instrument and is designed to have split resonances and variable vertical and horizontal mass in order to be tuned. The tuning is critical to optimizing the performance of any cartridge. For example

Bruce Thigpen
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.

Please note the comments from Bruce Thigpen "splitting the horizontal resonance frequency into two points". As I said there are multiple resonant frequencies to consider.

Clearly you still don’t get that your home brew efforts to remove this tunability by rigidly coupling the counterweight assembly result in a bass lift of 6-12db and increased distortion. Your addition of lead mass will increase these distortions further. Believe me Richard I have heard it, you apparently cannot.

Richardkrebs
Re my question re interaction between the two spring rates, …
I started thinking about this when Dover commented on the superior transient performance of his unipivot. The idea further coalessed when the tests were done with loosening the CW arm bolts. This would change the Q and possibly the res frequency of the CW assembly. Potentially reducing any interaction between the two springs, but not eliminating it.

My comments on the Naim Aro unipivot were pertaining to the superior preservation of the leading edge of notes - this is quite different from “transient performance”. Unipivots are mechanically coupled, whereas an air bearing is not rigid and loses some of the leading edge. It has nothing to do with Q as you claim. The addition of lead mass will alter the dynamic stiffness and compromise the performance of the air bearing. Capturing the leading edge requires secure tracking and speed, both of which are compromised by your addition of lead mass.

I do agree that it is possible that the spring could have some issues, and that is why I believe I got an improvement by using teflon rather than spring steel for decoupling.
Contrary to what you hear, when I trialed increased mass and coupled the counterweight rigidly with a low compliance cartridge I got bass that lacked coherency and was out of tune as is predicted by the maths and verified by Bruce Thigpen’s extensive testing. As a matter of point I reached this conclusion in 1986, well before Bruce published his test results. The website did not exist then. Frogman, Slaw and Chris have also come to this conclusion with a variety of cartridges and systems.

You choose to throw away two of the fundamental principles of the ET2 – maintaining a low horizontal mass and the ability to tune the horizontal and vertical resonances by using decoupled I-beams and variable effective mass for optimum performance.

It is disappointing that you are so rigid in your fixation with mass as I think you are missing an opportunity to substantially improve your system.

The preservation of low horizontal effective mass even with low compliance cartridges as prescribed in the manual and supported by Bruce's test results ensures the bass does NOT have a lift of 6-12db and improves tracking.

By my calculation AND what I have heard and experienced you have a bass lift and increased tracking distortion from your removal of the decoupled I-beam and the lead mass that you added.

If you prefer that, fine, but lets be clear, you can not call the misguided conversion of your ET2 into a high mass rigidly coupled arm an upgrade.