Eminent Technology ET-2 Tonearm Owners

Manitunc,
I use the original metal set up jig, but it is very easy to draw up a template on cardboard, measurements are here -
http://www.lencoheaven.net/forum/index.php?topic=4300.0

Hi Manitunc
You can also find the measurements for VPI and SOTA templates in the online ET2 manual - Part two on pages 62 and 63 at the back. Drilling even the one small hole that the ET2 needs, in a nice plinth ranks up there as probably one of the most stressful things I have done in this hobby. If using removable armboards ? I usually make a test one out of some material to practice with. Welcome to the thread.

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.

The writer, Dover, has written a great deal about air bearings lack of rigidity on this thread.

A few comments:

“In the Hifi News Review of the ET2 Martin Colloms concluded that the shape of the resonance passing through the air bearing remained intact.
This is not per se empirical proof that air bearings are rigid.”

Prove your assertion, thank you.

“Air bearings have compliance, and gimbal bearings can only be too tight (loaded) or too loose and can chatter.”

“The response above to my original post of 04-17-13 contains misinformation.
The comments plucked from the internet are irrelevant as they pertain to ball bearings and air bearings.”

Why is information on air bearings not relevant to discussion of air bearings?

“Unipivots are mechanically coupled, whereas an air bearing is not rigid and loses some of the leading edge.”

You have proof?

“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.”

Your statement regarding Bruce Thigpen is equivocal.

I suggest you contact Bruce Thigpen directly. Tell him you are the poster on Audiogon who has been promulgating the lack of rigidity of air bearings.

Ask him why he designed a floppy bearing and POST THE RESPONSE HERE unedited. Thank you.

The problems of adding mass to air bearing tonearms.

Here is Andy Payors ( Rockport 6000 ) view on it:

Andy Payor – Rockport 6000 Air Bearing Tonearm Designer - May 1996 review of the Rockport Series 6000.

"In linear trackers there is a big difference between the effective vertical and horizontal masses. Being a pivoted system in the vertical axis, a linear tracker's effective vertical mass is low because it consists of the relatively short armtube and cartridge. Horizontal mass is much larger: it includes the entire arm/sleeve assembly as well as the cartridge, all of which must be carried across the record and which do not benefit from being a pivoted system.
"Hang a small weight on the end of a spring and it bounces at a fairly high frequency over a short distance. Put a bigger weight on the spring and the rate of movement slows while the excursion length increases. The high mass of a linear-tracking arm in the horizontal axis can create a very nasty low-frequency resonance. The eccentricities due to the off-center pressing of virtually every LP made will excite this resonance as the system moves back and forth trying to track the shifting groove.

"In any arm/cartridge system, the arm should hold steady while the cantilever remains free to extract information from the groove. If the two were dancing partners, the cantilever would 'lead' and the arm would follow. In an undamped high-mass system the 'tail' (arm) begins to wag the dog (cantilever). Unwanted cantilever movement creates unwanted electrical output. In addition, any electrical output created with the coils uncentered in the magnetic gap is nonlinear, thus making it virtually impossible for the cartridge to act as a linear transducer, which is its job. Cantilevers can actually snap in undamped linear-tracking systems....In my opinion, a linear-tracking arm without damping is simply not viable if the goal is a 'reverse machine tool' accurately tracing what's in the groove."

This is precisely what I have been pointing out for the past 3 months.
To recap the debate:

02-16-13: Dover
Richardkrebs
Re: your ET2 mods. Here are a few points for you to consider.

Richardkrebs post of 02-15-13
“I have a view on linear arms in that the rules for pivoted arms and effective horizontal mass do not apply. In fact I have added a lead slug inside the bearing spindle 25 mm long…
This combined with the fixed counterweight means that the arm is HEAVY in the horizontal plane.”

This view is indeed strange. Many records are off centre. By increasing the horizontal mass of the arm significantly, when you play an eccentric record the increased resistance to motion from the additional mass will result in increased cantilever flex. On eccentric records your approach will result in phase anomalies during play back, increased record wear and probably cartridge damage in the long term.

02-23-13: Richardkrebs
Dover, for a given resonant system, all else being equal, addition of mass will lower the resonant frequency and reduce the amplitude of this resonance. ….Thou doth protest too much, methinks

03-12-13: Richardkrebs
Below this resonant frequency the cartridge is able to move the arms weight, start it and stop it, without cantilever deflection. I do not need to talk to cartridge manufacturers to confirm this. Do the math.

03-04-13: Richardkrebs
Your scaremongering may have dissuaded people from trying a simple reversible mod

Andy Payor and Bruce Thigpen both disagree with adding mass.
They both support my analysis that adding mass creates higher distortion, unwanted cantilever motion and non linear response from the cartridge.

Please note the key points Andy Payor of Rockport makes.
High horizontal effective mass results in:

• The high mass of a linear-tracking arm in the horizontal axis can create a very nasty low-frequency resonance.

• The eccentricities due to the off-center pressing of virtually every LP made will excite this resonance as the system moves back and forth trying to track the shifting groove.

• In an undamped high-mass system the 'tail' (arm) begins to wag the dog (cantilever). Unwanted cantilever movement creates unwanted electrical output. In addition, any electrical output created with the coils uncentered in the magnetic gap is nonlinear, thus making it virtually impossible for the cartridge to act as a linear transducer,

• Cantilevers can actually snap in undamped linear-tracking systems

Andy Payors view of the world supports my argument for maintaining the ET2 as a low mass design and supports the use of “magnetic” damping. Andy Payors comments on air bearing tonearms are exactly the same as Bruce Thigpens.

Bruce Thigpens patented decoupled counterweight design is specifically designed to deal with the unwanted nasty peak resonances inherent in linear tracking tonearms with a high horizontal effective mass.

The suggestion of adding lead mass and removing the decoupling mechanism in the ET2 is inadvisable. It results in higher distortion and non linear response. Andy Payors endorsement of Bruce Thigpens low mass approach leads me to wonder why anyone would continue to advocate adding lead mass and removing the decoupling of the I beam from this sophisticated and ingenious high end tonearm.