Eminent Technology ET-2 Tonearm Owners

Pseudo science from Dover:

"removed their fluid damping and replaced it with electromagnetic damping which has the benefit of not inhibiting movement until the movement happens."

Pseudo science: its identical with fluid damping - there is no damping unless there is movement (same with the dampers, so called shock absorbers, on your car. Drive slowly over a speed hump and the whole vehicle is raised, ie there is no movement, and no damping).

Dover.
Secondary resonance? You mentioned this twice in your post 05-15-13. The frequency numbers you used were 3x Fr for this. The 3x Fr figure is the multiplier used by BT where he considers the amplitiude and phase anomolies above Fr have fallen to a level that is benign. Think a normal distribution curve. In our industry, we use a 6x Fr multiplier since we operate in a much more conservative environment.

There is no 6-12db increase in amplitude at 3x Fr or even Fr. The arm is damped with an oil trough. See the graph and read the technical notes from BT, posted by Chris on 05-14-13. Note also, Bruce set up the arm with a "deliberately high Q" and low compliance cartridge.

You let slide and error in my calcs because other parts of the arm have their own resonance. Sorry No. See BT's own formula for calculating horizontal Fr. It does not take into account these other structural resonances.
That said these other resonances can have an effect on the shape of the resonance curve but the fundamental determinent is the horizontal mass.

There are 2 possibly 3 structures in a standard ET who's own resonance is low enough to have this impact. The decoupled counterweight, which is deliberate. The relatively compliant gooseneck and the o'rings in the manifold. The o'rings are a maybe since they typically allow movement towards and away from the record, not laterallly.
(Anyone interested in observing how compliant the goose neck is could try this test. Do it at your own risk!
Lift the arm with the lifter and put the stylus guard on. Travel the arm fully inwards and then lightly push the spindle where the wiring plug is against the bearing sleeve. Now lightly pull the cartridge end of the wand towards the outer edge of the record. You can clearly see deflection of the wand. The goose neck is flexing. If you are able to let it go quickly, you will see it momentarially oscillate. If chris did this with the aluminium goose neck he would need to literally bend the wand to get any deflection.)
All three of these structures have been altered (stiffened) or eliminated in my arm since in my opinion they all compromise "leading edge" and have other negative consequences.

The other compponents of the standard arm have, IMO less impact on leading edge performance with the airbearing having none at all. It's resonance is in the 100s of Khz, way outside the audio spectrum. Spock15's experience with his air bearing arm seems to support my view. However it is the cacophony of all of the individual resonances amongst many other factors that makes up the "sound" of the arm. On that front we agree.

What an extraordinary hobby this is. RK and I share this wonderful aluminum ET2 Gooseneck that he made - I really like it.

At this current (snapshot) in time however;

RK’s tonearm objective is adding more control and damping to his Krebs Arm.

I meanwhile am trying to figure out how to go wireless with my ET 2.5.

Think Free Willy !

Maybe my IT background biases are showing. With that the damping fluid should be coming early next week with the adhesive tape. Look forward to trying it again after all these years.

Welcome to the thread Spock15. Listing what your air bearing and pivot arms are would be nice to those of us reading for reference.

Thekong has provided some excellent perspective between the Rockport and ET2.

Hi TheKong – were you able to find the lead to make the counterweights at those tire shops ?

Look forward to Rugyboogie providing perspective with the Kuzma Airline and ET2 soon – Congrats on getting an ET2 - RB.

Now we need a Swedish fellow or gal :^) to come on here to help provide perspective on the Air Tangent and ET2. Maybe I will look for one (Air Tangent) to close this loop. However no remote control version for me.

As I type this Ottawa to Toronto area of Ontario experienced a 4.8 earthquake – a little shakey.

As I type this Ottawa to Toronto area of Ontario experienced a 4.8 earthquake – a little shakey.

Sort of like my JMW 12 unipivot. :^)