04-30-13: John47
The writer should get this, from Franc Kuzma:
'At hi-fi shows, we routinely ask people to pull or twist the Air Line tonearm on a Stabi Reference turntable. The whole suspended mass of 24kg (52.8 lbs) moves back and forth for 1/4!9 while the air bearing maintains zero friction! Most people are shocked.'
John47 - thank you for this. It confirms that the ET2 should NOT have additional mass added to it by removing the decoupling and adding lead.
The Kuzma bearing operates at about 60psi whereas the ET2 bearing operates at a much lower level. One cannot just increase the pressure; the manifold, airflow and bearing tube have to be designed specifically for the target operating pressures. Perhaps Ct0517 could test his ET2 with 24kg on the end of it.
Eminent Technology have 3 manifolds available
- The original low pressure
- The original high pressure
- A large spindle high pressure
Increasing the pressure generally increases the stiffness.
Eminent Technology website
ET II Large Diameter High Pressure Manifold - This new manifold is a direct replacement for the original high pressure manifold. You just remove the old spindle and push the old manifold out of the base and then insert the new manifold into the base and slip in the new, larger and heavier spindle. The new manifold allows the spindle, which is suspended on the air bearing, to be increased in diameter by about ¼th of an inch. Now ¼th of an inch may not sound like much, but it is the surface area of the spindle within the manifold that helps determine the stability of the bearing. The surface area of the new bearing is about 25% larger than the surface area of the old bearing, plus the tolerances are closer than in the original high pressure manifold. This makes for a much stiffer bearing.
These comments from Bruce Thigpen do not agree with the view opined in the following post
04-23-13: Richardkrebs
Although the bearing uses air which we know to be compliant, at the frequencies of interest, the bearing medium is stiff.
So one could surmise that the Kuzma does have a stiffer bearing if you accept that Bruce Thigpen knows what he is talking about, which I do as he is well studied in Physics, Maths, Audiology and has been designing air bearings for some 30 years.
Eminent are in the process of designing a new higher pressure bearing
Eminent Technology website
We are also developing a very high pressure bearing for the ET 2.5 which will operate between 20 and 80 psi. Please contact Eminent Technology if you have any questions.
The main advantage of the ET2 over the Kuzma is the low horizontal inertia and split resonance tuning capability due to the decoupled counterweight assembly.
These features ensure there is no bass hump and provides superior tracking of the groove. Superior tracking will preserve the harmonic structure of notes.
A good example of this is the test results that Frogman posted
03-23-13: Frogman
For instance, I am not yet convinced entirely that IN MY SYSTEM, going for the lightest weight/mass possible is the way to go. Yet, and speaking of loosening the laces, I decoupled (loosened) the I-beam yesterday, and lo-and-behold, on Donald Fagen's new release "Sunken Condos", what had previously been little more than amorphous low frequency energy suddenly became notes that I could discern the pitch of; completely the opposite of what I expected given my experience (extensive) experimenting with springs of different compliances (single, double, etc.), and the reason I had not tried it yet.
Bruce Thigpen confirms the problems created by increasing the horizontal inertia.
Bruce Thigpen
If the weight is coupled the system resonant frequency would be extremely low, a resonant frequency at 3Hz with a significant rise in response (6-12dB) results, which would affect tracking slightly because of the asymmetric position of the cantilever, we opt for splitting the horizontal resonance frequency into two points and lowering the "Q" which improves tracking.
More important than tracking, the intent was to reduce the modulation effects of low frequency energy (FM and AM) that increase distortion in the cartridge
This has been the thrust of my posts over the past few months – adding lead and removing the decoupled counterweight takes away to benefits of the ET2 split resonance low mass design, causes an unnatural lift in the bottom end and increases distortion. These suggested modifications eliminate the main benefits of the ET2 design.
Frogman, Slaw, Ct0517 and my own testing concurs with this. We have all achieved superior results with the correct tuning of the decoupled counterweight I beam.
