Eminent Technology ET-2 Tonearm Owners

@lewm 

 I am wondering why mounting a large weight close to the pivot point makes any difference as far as overcoming the air pressure and collapsing the air suspension , 

Because the air bearing carries the mass of the arm/cartridge/counterweight in total - If you have a larger counterweight that increases the total moving mass to above what the bearing has been designed for then it could collapse.

@nandric 
From what I have read and understood, the removal of the post has only to do with eliminating the bot-trigger word "me.t..." to save the discussion thread being flooded with spam. Using this abbreviation is "logical" and understandable in verbal communication but it triggers the spam button on web-based discussion platforms.
Removal of that post had IMO nothing to do with something personal against you.

@ct0517 & @lewm 
Using the same counterweight spring, to half the lever, ie. the distance of the counterweight from the pivot axis and to double the weight increases the resonance frequency of the counterweight-spring system (by SQR(2) methinks).
Ie. bass pulse / group delay aspects come into play too. With the decoupling the resonance system is more complex than without (nifty 4th order instead of 2nd order).
Increasing the weight of the assembly / counterweight increases the "weight stress" *and* the "leverage stress" on the air bearing. Optimally, in mid travel of the arm, the center of gravity of the whole arm should be centered in middle of the air bearing. (Something eg. the Kuzma, Air Tangent and adanalog arms are by design). A short i-beam / short lever severely shifts the center of gravity toward the end of the bearing and increases the leverage stress. Ie. the bearing works less stable.

@lewm

Lewm

I normally don’t contribute to this thread, because I do not own and have never owned an ET2 or 2.5. However, I concede that it is probably a great tonearm. But when you speak of Newton, keep in mind that the net force exerted by a small weight at the end of a long lever That is required to balance a cartridge at a specific VTF will be the same as the force generated when you use a larger weight mounted closer to the pivot or fulcrum. Therefore I am wondering why mounting a large weight close to the pivot point makes any difference as far as overcoming the air pressure and collapsing the air suspension , Assuming the same VTF is thereby achieved in both cases.

Lewm

Setting VTF on a pivot arm is two dimensional. With the ET 2, the mass is adjustable so you could call it a three dimensional setup. Did you know that the counterweights are decoupled by a spring, and that the cartridge itself only sees the vertical mass and not the horizontal mass ? The word "stressed" is a better word than "collapse" Many years ago I never did collapse it with extra DIY weights, but if I added even more weight who knows. The experiment was over before that.

Page 9 of the ET2 manual on design. Adjustable Effective Mass

The effective mass of the tonearm is adjustable, both vertically and horizontally. The arm has low-medium mass vertically and medium to high mass horizontally. Four counterweights allow the vertical / horizontal mass to be changed. For example; if the user decreases the amount of counterweights used, and moved this position back (higher scale number) the horizontal inertia of the tonearm would go down and the vertical inertia would go up.

You can download the ET2 manual here

http://www.eminent-tech.com/techsuppt.htm

If you read the first 10 pages of the manual and the tech section, I believe you will get a good understanding of the tonearm.

Some ''priviledges'' of ''knowing kinds''  are very curious. My  experience

with ''communist security paranoia''' about their own security can  be

comapared with '' Western paranoia'' about so called ''private security''.

The suggestion is ''for you and me''. Two of my contributions are

delited in two days time , obviously by some '' considerate members''. 

I was able to avoid communsit kind and think to be able to avoid ''Western

kind'' . This is my last contribution to this forum.

Is there anybody reading here, who is experienced in modeling mechanical systems as equivalent electronical circuits?

I was not able yet to figure out the equiv. circuit for the (horizontal) 4th order system tonearm / decoupled counter weight myself. I think this could be very helpful in understanding and optimizing the setup.

The longer i-beam allows much lower resonance frequencies ie. potentially a wider tuning range.
Intuitively, tuning the counterweight res. +\- precisely to the spindle/arm/cartridge resonance and optimizing the damping should „drain“ the main resonant energy, as shown in certain plots of the decoupled Dual counterweights in the 70s.
I‘d like to see and play with these interactions in a quicker, less time-consuming medium than the actual tt setup (with measurements another PITA).

I was able to optimize the mechanical panel resonance of aMaggie MG 3 and MG 3.3 in a similar way, but kind of a hybrid mechanical/electrical filter. It worked :-)

@nandric
your posts and experiences with audio are still appreciated. The removal of the post has nothing to do with paranoia, neither western or communist. It‘s only about keeping the spam cleaning task if the moderator low, by removing trigger words for bots.