Eminent Technology ET-2 Tonearm Owners

Hi John47 :^) - raising fraternal twins can be entertaining too. My wife and I are into our 18th year of dealing with their demands in “stereo”. This hobby and a little sense of humor has helped me through it to this point. The twins have shaped my humor however – made it more cynical I think. My wife doesn’t care too much for it. She also doesn’t care for music above 70 db. Probably explains why I am here.

Rugyboogie - welcome to the thread. Am curious if you or other Kuzma Airline owners have ever considered any modifications to that tonearm?
Cheers

Ct0517 - fyi
Magnets can be a little eccentric. On Richardkrebs deck they may prefer the wand end because they get a better view of the cantilever doing her one legged tantric yoga exercises.

There is a sound engineering reason to put any mag dampening to be at the wand end of the spindle. Since the mag tends to resist spindle movement, it acts as a pivot for any non axial spindle motion
Since the cartridge is at the end of the wand and not at the end of the spindle, there is a force moment induced by stylus movement. The spindle can, at frequencies below the air bearing resonance point, move about this pivot point in a non axial manner.
Having this pivot point at the wand end causes less teter totter due to spindle sleeve clearance than would be the case if the pivot point was at the counterweight end. This benefit is clearly audible.
Exactly the same design feature is present in TT's with inverted main bearings.
Of course the mag is closer to the signal wires.
The choice is yours.

Thanks Dover, Ketchup and Richard for addressing my concerns.

Well, I must admit I was somewhat skeptical about magnetic damping, but I am now convinced of the benefits. Some preliminary observations:

So far, I have used a single refrigerator magnet that conveniently detached itself from the back of a cooking timer. I glued this inch-squared flat magnet to a small block of glued layers of cork about the same size as the magnet. I situated it on the wand side of then arm pillar; frankly, only because I still have the damping trough attached to the pillar (with paddle disengaged). I plan on trying it on the other side, as well as trying other, more powerful magnets. The magnet is as close as possible to the spindle without touching it.

I listened to the same musical selections several times, with and without the magnet. The results are relatively subtle but unmistakable. There is a general "cleansing" of the sonic picture; as if a fine mist is removed. Bass definition is improved with an increase in one's ability to hear pitches in the bass; as opposed to simply low frequency energy. The highs gain a bit of refinement and sound slightly less ragged. On "The New Breed" from Donald Fagen's new release Sunken Condos, Walt Weiskopf plays both alto and tenor saxophones. Without the magnet, it is very difficult to hear when he plays alto vs tenor. With the magnet, more of each horn's individual character can be heard. Also, for an LP with otherwise very good sound, the bass, while being powerful and very well extended, has a strange "drummy" quality with less than good definition. The magnetic dampening brings a welcomed slight improvement in pitch definition. Curiously, the soundstage seems slightly smaller with the magnet; perhaps a result of the increase in control and definition. The differences are not earth-shaking by any means, but definitely worthwhile. I have not experienced increased volume; perhaps with the more powerful magnets.

Biggest surprise of all: record surface noise seems reduced. LP surfaces are quieter, and the loudest clicks and pops sound less obtrusive with a more subdued character.

More to follow.

Richardkrebs -

I'm a little disappointed you dont think outside the box, or in this case arm.
What about running 2 ET bearings in a T bar configuration, armtube in the middle.

You like magnetic dampening but worry about the eddy current. Try standing on your head and thinking upside down. You dont have to use the bearing tube.
Why not use a magnet as a counterweight and an aluminium bar mounted on the plinth. Why not go the whole hog and put an accelerometer on the bearing housing, that way you can measure the resonance and employ electromagnetic dampening driven from a feedback loop and active servos to dial out the exact resonance.

What I do know is that added mass will have altered the dynamic stiffness of the bearing and the fundamental resonance. It will increase the instability in that air bearing. You are running 12psi - this is on the lower end of what most are running ET's. With the added mass you are increasing the very instability you are complaining about with the magnets.
Have you measured the dynamic stiffness and fundamental resonance after adding mass ?
Have you calculated how much you need to increase the pressure by to provide the same level of rigidity in the bearing as the standard arm ?
Have you measured the impact in the high frequencies of being able to achieve the same level of rigidity with less mass ?
When it comes to resonance mass is your enemy. Do you put lead in your gumboots for a smoother ride when you go tramping ?

Perhaps you should resign yourself and go to a unipivot. An air bearing will never be as rigid as a unipivot - you are losing so much of the leading edge of notes. That would solve all your anxieties and give you a whole new set of issues to fret upon.

PS The tantric yoga is no joke - stand on one leg, put the other to your ear, and you may hear a little more bottom end.