Eminent Technology ET-2 Tonearm Owners

Richardkrebs
Referring to your last post 03-12-13: responding to Dover.

At frequencies below resonance the cantilever is free to push the mass of the arm sideways. This does not defy physics, it is physics.

Correct

In other words the cartridge suspension is stiff enough to accelerate the arm mass sideways. .

That is an assumption that will depend on the compliance of the cartridge. If the compliance is low enough then possibly, but before the acceleration commences the cantilever will flex.
You seem to be unaware that cantilevers are mounted in a rubber elastomer that is not rigid.

Think of a tension spring with a weight suspended at one end. This combination will have a resonant frequency. If you hold the spring end opposite to the weight and move it up and down at a frequency below resonance the weight will move up and down in sync with your movement. The spring will NOT stretch as a result of this movememt. .

A curious analogy, yet again, you compare apples and oranges.

Your analogy compares
1. Holding the end of a spring with a fixed weight on the other end
to
2. The stylus point sitting in a groove, not held, at the end of a cantilevered beam, at the other end of which is a rubber suspension ( not a spring ), and the other side of the suspension has a mass loading that is constrained at 90 degrees by the rigid air bearing some 6 inches away.

Your analogy is a triumph of the imagination to consider these two scenarios in the same manner. Your discourse on resonant frequency is irrelevant.

Quite frankly I cant be bothered doing the maths, but I defy anyone to show me a cantilever that does not flex when playing an eccentric record. This does indeed defy physics unless you have a cantilever that has zero compliance.

No, the video does not show the cantilever, that is why I asked him if it was a problem.

If you agree the video does not show the cantilever then why do you repeat the following statement that is misleading?

I repeat the video is shown specifically to allay fears of problems due to high horizontal mass. .

I assume from your lack of response that you have not sought any advice on this matter from any cartridge designers. I would have thought this was the first port of call for a thorough and complete understanding of the problems of navigating eccentric records.

Thekong

Thanks for sharing your experience. I agree with Fremer.
Thigpen does appear to hold patents on the decoupled counterweight.
Whereas Walker uses a fixed counterweight at 45psi in the Proscenium, Richardkrebs advocates using a fixed counterweight, adding additional lead weights and running a relatively low pressure of only 12psi in his ET2.
In my view his modifications increase inertia and increase the loading on the cantilever suspension when side forces from eccentric records are presented to the stylus. He employs no dampening to control this increased mass. Once it moves there is more induced cantilever flex from overshoot. This is way outside Bruce Thigpens original design concept of low mass and decoupled counterweight and should in no way be construed to be an ET2. There is always the risk of cartridge and or record damage with Richardkrebs added mass-low pressure approach.
Richardkrebs advice in a previous post for those concerned about possible cartridge and record damage was, quote

People are free to try, it is entirely their choice. Install an alternate cheap cartridge, play a record you don't like, if you are that worried about damage to same.

This advice is probably about the only thing that Richardkrebs and I could agree on.

very interesting discussion guys.

I am personally going on over 9 years with the ET2’s – never had a problem with a cartridge.

I think I represent a typical music lover – meaning - I own xxxx records. At any one time there are xxx in 4 or 5 rows on the floor against the wall in my room that get cycled.
Now none of them are eccentric enough to cause the spindle to move around like crazy. Most of the time I can barely see any movement in the spindle at all. I’d have to look really hard.

Very interesting discussion on the various air bearings. It should be noted that of the ones mentioned so far , the Kuzma and ET2 I believe are the only two that can be mounted on any TT. There is the Terminator too (it seems from pictures/videos to occupy alot of space on the TT?) Maybe DG can elaborate? Its a BIG DEAL in my book to not be TT dependent. And fwiw - Any tonearm comparisons should be made imo mounted on the same table as this is a hobby about resonances and vibrations.

So I have to ask here - Richard, Dover, Kong, others ..... what kind of records are you guys actually playing that you are so worried about eccentricity of the record ?

I refer back to this post with data from the ET2 manual.

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325551242&openflup&372&4#372

Specifically the wording.

This means that any given cartridge works against lower horizontal forces in the Model Two tonearm (.1 gram or less) compared to a conventional arm (.2 grams/gram vtf). These figures apply if you use records that are not severely out of round. If you like to play severely eccentric records, ones with runout of greater than 1/8”, then we suggest you use a low mass pivoted arm.

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Richardkrebs - We went on to talk about potential problems with cantiliver flex. His response was the resonant frequency due to the combination of a typical low compliance cartridge and horizontal effective mass was in the region of 2.5 -3.5 hz.(this has been published by them elsewhere), this is well above the 0.55 or 0.75 hz for 33 or 45 rpm eccentric records. Therefore the cartridge does not "see" this movement.

Richard , so as shown above, Bruce has measured the lower horizontal forces in the Model Two tonearm (.1 gram or less) compared to a conventional arm (.2 grams/gram vtf).

Are you able to get us the actual “lower horizontal force number” in the Kuzma Airline from Mr. Kuzma.

I am very interested in this number – this is where the tire hits the road to me, no ?
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I have to admit something here to everyone as well, since I have been giving the discussions we have had thought.

I really like the fact that the ET2 does not put any constraints on me as far as the type of cartridge I can play, anytime and anywhere.
I can put on a Sonus Blue Gold with a single leaf spring,
• Dynamic Compliance: 50 x 10-6cm/Dyne.
• Tracking Force Range: 1.0 to 1.5 grams.

than switch it over to a triple leaf spring beam with my XV1. Is this flexibility not worth something ?

sorry for the following asterisks but this "IBM dos like" based forum does not allow for bolding and colors.

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Is there another tonearm in existence that allows for the above to occur regardless of cost ?
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btw - If I do find a record I like alot - that is so off centered (runout of greater than 1/8” as Bruce says)
and cannot be replaced. Why not just drill out the center hole and use a heavy weight on it ?

Richard/Dover/Slaw - is this not possible ? You guys have discussed drilling out of holes before....

Cheers

correction last post - I am in my 10th year now with the ET2's. When this thread started it was 9 years. lol.

The ET2 gooseneck – the part that connects the armtube to the spindle is made from Carbon Fibre. I asked Bruce about making one in aluminum. It can be done in a special run if there is enough interest.
I told him I would find out how many are interested. If you have an interest you can contact me at
bcpguy(at)bell(dot)net

Cheers