Eminent Technology ET-2 Tonearm Owners

Thanks for the info Richard.

The thought that there may be more going on with the decoupled counterweight was triggered by your post where you quoted BT where he said that the ibeam had a natural frequency of 2-5 hz.

The figure I quoted is from the manual and I believe it is for a stock single I Beam with the weights that are supplied with the stock ET2 tonearm - not the ET 2.5 – which we agree is a different animal with different resonances.

I gotta believe that adding a leaf spring plus adding the ET 2.5 larger spindle changes things?

I would need to confirm this with Bruce.

Dover - if I may say - you come across as a real hard ass sometimes in your posts; but you have a very direct sense of humor. lmfao.

btw - what I just said my kids say to me alot. they unfortunately both being only 18 have not yet seen alot of my humor. I try to save it for you guys as I my wife just doesn't appreciate it either. This thread is 11 pages long now. She will never be able to trace back to what i am saying here.

Richardkrebs

Astounding!
After 25 years of tinkering with your ET2 tone arm, you now reveal in your recent posts that you have only just worked out how the arm works.

Only now have you realized that the sprung I beam has a resonance and the tuning of the I beam and the number and position of lead weights used is critical to optimizing the performance of the ET2. This is clearly explained in the manual and was discussed at earlier on this thread..

Let me quote your recent posts:

03-19-13: Richardkrebs
I don't have any proof of this, it is just a recent thought. While higher or lower weight is obviously a factor, I think that the one leaf spring, two leaf spring plus number of weights thing, has probably a whole different set of cause and effect issues. So with reference to a rigid or sprung counterweight beam, it is probably an all or nothing event. In other words because we have the "potential" interaction of the swing frequency of the beam and the resonant frequency of the arm assembly, depending on the number of leaves and the number of lead weights used. It could be that tuning here with springs and weights (and their position) is at least partly to do with sorting this possible frequency interaction rather than just the weight or stiffness employed. Others may have already thought of this but, it is just an idea to put out there for comment.

03-20-13: Richardkrebs
The thought that there may be more going on with the decoupled counterweight was triggered by your post where you quoted BT where he said that the ibeam had a natural frequency of 2-5 hz.
This is close to the resonant frequency of the arm itself. This could have performance implications.

For the last 5 weeks I have been saying that you do not understand how this arm works. At the same time you have been promoting your modifications that include adding significant amounts of lead mass and removing the decoupling of the I beam which, I keep repeating, takes this arm out of its designed operating parameters.

Your latest revelations make it clear that you have not understood the set up procedures described in the ET2 manual, nor do you understand their purpose and what principles they are based on.

For this reason I would continue to caution readers that your advice on adding lead mass, M10 bolts and coupling the counterweight to the ET2 should be disregarded.

Dover.

....Sigh.....

My comment re "All or nothing" was designed to open useful dialog on the subject. I was trying to be subtle.

So now, not so subtle..
Do you really think that it is a good idea to have a spring driven mass, ( cartridge and arm ) attached to a spring suspended mass ( ibeam and counterweight). Both with resonant frequencies in the same neighbourhood?
If you refer to the math and resonance graph I posted, it shows that this can be problematic. The two resonances need to be far away from each other to avoid any interaction. At best a good compromise can be achieved with adjustment of the parameters. I don't like compromises. Better to eliminate one of the compliant joints in the system completely.

As I have said earlier. If fixed, the counterweight beam must be very strong. I note that Kuzma also know this as the counterweight beam is substantial indeed. Three springs don't cut it.

It is no accident that other arm manufacturers have a rigid joint there....it simply sounds better.

I don't understand why you are so set on trying to stop people experimenting on this area of the arm. It will do no harm and at the very least add to our collective pool of knowledge. A big hand will not come out of the sky and squash anyone who deviates from the original design parameters, it will be a bit of fun and it may just bring the owner closer to the absolute joy of listening to music, which is what this hobby is all about.

Put on your knitwear cardy so don't catch a cold, your thick lensed glasses so you don't fall, then pop out and replenish your Prozac.

Chris (such a lovely guy):

"You come across as a real hard ass .."

Acronym: PITA

BTW did Richardkrebs pick on you at preschool?