Eminent Technology ET-2 Tonearm Owners

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.

Dover - Andy Payor and Bruce Thigpen both disagree with adding mass.

Cant speak for Andy Payor but this is not true with BT. The original ET2 came out when MM’s were popular. When heavier less compliant MC’s became popular. Bruce introduced the heavier 2.5 spindle as well as heavier CF and Magnesium arm wands to deal with MC’s. This has already been discussed here.

http://www.eminent-tech.com/magarmtube.html

thats an old web link btw - the new price for the mag tube is on Bruce's website under Et 2.5 parts list.

A couple of folks here including Frogman and RK have come up with diy solutions. Frogman has used special armtube wrap. RK has added weight to the armtube and spindle. I’m sure others have done other things. Frogman noted as well as BT and myself that the 420str MM seems to gel better with the lighter aluminum armtube. My 420str is now on my ET2.

Dover - The Kuzma bearing operates at about 60psi whereas the ET2 bearing operates at a much lower level

Well this is not totally true either – other than the everyday ET2 with the original pumps Bruce would also custom build them for any PSI and did. There are many around. My ET2 HP based on the notes that came with it (it was bought used) is a 50 psi manifold model. My ET 2.5 manifold was custom made for 19 psi by Bruce for me based on my requirements. Why 19 psi ? this is covered on the first couple pages of this thread.

So there are many ET2’s out there that have manifolds set up for really high pressures. These were custom ordered. If you want to know if you have a high pressure manifold or not. Push it out – inscribed on it will be XHP or HP. The other method is to hook it up to a compressor and start adding in PSI and see what it can take. If it came with a WISA is was meant for 5-7 psi. The original pump was in the 3 3.5 psi range.

imo - There are three different areas being discussed here and they really should he kept separate to avoid confusion.

1) Adding weight to the ET2. As mentioned above and in previous pages here Bruce added weight to the spindle and changed the armtubes for MC’s. If Do-it-yourself (DIY) - adding weight to the spindle and armtube. Consideration needs to be given to vertical and horizontal masses. The ratio is important. Its important to remember that the armtube/armwand affects both the vertical and horizontal masses.

2) Decoupled IBeam - The ET2 design is de-coupled. This is a big plus to me right now as it allows me to use any cartridge I want. If you couple it – its no longer an authentic ET2 design. Its your own unique design. Those using it this way seem to have it tailored the setup to one cartridge only? This is their choice.

A bigger evil for me than this ....my pivot arms can’t go straight. No one seems to have an issue with this?

It’s like spending thousands on a new car...on the drive home I discover it pulls to the right. I call the dealer about the problem. His/her answer to me is to let some air out of the front left tire. :^(

Would you accept that? Well - All pivot arm owners including me do.

3) Air bearing stiffness. Leading edge notes. My boogie test is older lps up against Master tape dubs – no issues here for me based on my ears. I’m good.

Dover – I am curious to know for fun what your boogie test is?

Cheers