Eminent Technology ET-2 Tonearm Owners

04-29-13: Ct0517
04-27-13: Dover
.....dont be embarrassed about using spotify, I've heard spotify streamed through an Ipad.........

Dover – if you know Spotify then you would know its not available in Canada. Have never heard it. My post on that article had everything to do with music itself – regardless of format and nothing to do with the equipment. It appears my post was misunderstood by you ? and maybe others so the reason for my post.

Dover –in this picture is a mechanically grounded unipivot. Please note the way it has been setup. What do you think happens to the sound when it is set up this way ?

Here is another
example
A little more extreme ?
Ct0517 (System | Reviews | Threads | Answers | This Thread)

Ct0517,

Spotify - Ct0517 since you mentioned this I thought I should share my experience. Digital can be a very useful tool to benchmark our analogue front ends to, particlularly in terms of speed, timing, transparency and identifying colourations in our systems. It can provide a useful benchmark due to its consistency whilst we tune our analogue front ends. That is not a value judgment on quality - it is the consistency that is of value. Nevertheless, I have heard Ipad/DAC front ends sound better than poorly set up or badly modified analogue TT's. I was unaware it is not available in Canada as I dont live there.

Mechanical Grounding - Please explain your point. When I use the term mechanical grounding it was in the context of the bearing itself, not how the arm is mounted.

Naim Aro tonearm
By Markus Sauer • Posted: Jun 5, 1995 • Published: Jun 5, 1993
The bearing is the ARO's stroke of genius. In other unipivots, a sharp pin is mounted to the turntable and the arm carries a cup which sits atop the pivot point. The ARO's arm carries the sharp tip, resting this atop a stationary cup: a true mechanical ground, and the only spiked tonearm I know of!

I've had less experience with the Eminent Technology ET 2 and Graham 1.5t than with the other two arms, and so don't want to make too strong a statement, but I don't think they can hold a candle to the ARO in the boogie department. The ET 2, on the other hand, presents an even more spacious soundstage and possibly even lower distortion, due to its superior geometrical accuracy.

There are clearly pro's and con's with any piece of equipment. In this case of the Naim ARO and ET2 we are trading off the more accurate preservation of the leading edge from the mechanical grounding of the Naim bearing for the superior soundstaging and lower distortion of the ET2 from the tangential geometry.

This notwithstanding that adding mass and removing the decoupling from the I beam and counterweight assembly will of course promote distortion, negating the benefits that are inherent in the ET2 as has been explained by the designer Bruce Thigpen.

Bearing Stiffness – Naim Aro vs ET2

04-21-13: Richardkrebs
c)....the air bearing employed on these arms is effectively rigid at audio frequencies. So they should look elsewhere when looking for the cause of compromised note leading edge performance.

04-16-13: Richardkrebs
I started thinking about this when Dover commented on the superior transient performance of his unipivot. The idea further coalessed when the tests were done with loosening the CW arm bolts. This would change the Q and possibly the res frequency of the CW assembly.

My comments on the Naim Aro unipivot were pertaining to the superior preservation of the leading edge of notes - this is quite different from “transient performance”. Unipivots are mechanically coupled, whereas an air bearing is not rigid and loses some of the leading edge. It has nothing to do with Q. The addition of lead mass will alter the dynamic stiffness and compromise the performance of the air bearing. Capturing the leading edge requires secure tracking and speed, both of which are compromised by the addition of lead mass or removal of the decoupling.

04-23-13: Richardkrebs
Stiffness
Many years ago I remember reading an audio magazine which tested the rigidity of the ET2 bearing. It may have been Martin Colloms, but I can't be sure. This was done, again from memory, where accelerometrs were used and a sweep frequency was applied to the spindle. The result showed a bearing that was stiff at audio frequencies.
This is explained by the design of the bearing (it's self centering characteristics) and its extremely high resonant frequency. Many times higher than the audio spectrum. Although the bearing uses air which we know to be compliant, at the frequencies of interest, the bearing medium is stiff.
I also show here a quote from an industrial air bearing manufacturer. While these a big load bearing devices, their design is virtually identical to the ET2

"Outstanding stiffness for small deflections Most engineers visualize an air bearing as being like a hovercraft, and they erroneously conclude that a bearing which floats on air cannot be very stiff. Actually these gas bearings are many times stiffer than a ball or roller bearing. Sapphire orifices within the bearing gap control the pressure in a film of air which is only 0.0003 inches thick. As a load is applied to displace the bearing rotor or slider, the gap decreases very slightly on one side, reducing the flow of air through the adjacent sapphire orifice. This results in a pressure increase in the gap on this side which pushes the rotor back to its original position. In essence, the air bearing is a servomechanism with closed loop control, and maintains a uniform gap in spite of external forces that may be applied. This results in bearing stiffness of millions of pounds per inch for small deflections. Stiffness is linear and does not change with temperature. In contrast, ball or roller bearings have almost no stiffness unless heavily preloaded. The stiffness of a ball bearing is not linear, and varies considerably with temperature."

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. They were copied from the following website
http://www.space-electronics.com/Products/air_bearings.php
The Naim unipivot does not use ball bearings.

The Naim Aro is mechanically grounded whereas the air bearing is not. Unipivots are the most rigid coupling you can get in a tonearm. Air bearings have compliance and gimbal bearings can only be too tight (loaded) or too loose and can chatter.

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.

I note that most users of the ET2 have increased the air pressure up to around 19psi and have reported improvements to the sound as the pressure is increased.

When the operating air pressure is increased, the following operating parameters are altered - the Q of the system, the dynamic stiffness of the bearing, the resonance frequency of the air bearing itself, the shearing forces are changed.
All of these changes will of course be in themselves be difficult to calculate as the results will vary depending on the resonances in the I beam and cartridge and masses involved.

This is precisely why Bruce Thigpen backs his physics and maths up with extensive testing.

Issues Created When Adding Lead Mass and Removing the Decoupling of the I Beam on the ET2

04-21-13: Richardkrebs
b)....a heavy arm, when and only when, connected to a low compliance cartridge is a high performance, viable alternative

This statement is not correct within the context of the ET2.
Adding Lead to the arm increases the horizontal mass.
Removing the decoupling on the I Beam increases the horizontal mass.

The ET2 is designed with a target horizontal mass to be used in conjunction with a decoupled I Beam & Counterweight.

Increasing the horizontal mass increases distortion due to the additional side loads on the cantilever & tracking is compromised.
Increasing the horizontal mass creates a large peak resonance in the bass that also affects tracking and increases distortion.

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

When you add mass and remove the decoupling how big is the resonance in the bass?

Bruce Thigpen has measured up to a 6-12db lift in the bass when testing the removal of the decoupling from the I beam

04-23-13: Richardkrebs
Maths and Physics.

Amplitude
A few weeks back I posted a transmissibility graph showing the effect of excitation frequencies at various multiples of the resonant frequency. This graph can be used to show relative resultant amplitudes for known resonant and excitation frequencies.
For a standard ET2 using in my case a Shelter Harmony, we get a resonant frequency of 8.4 hz. On my heavy arm, this frequency drops to 5.3 hz. If we take the lowest frequency of interest to be 20hz we get multipliers of res freq of 2.4 and 3.8 respectively.
By applying these multipliers to the graph we can see that the system which resonates at 8.4 hz shows a small rise in amplitude about 15%. If we now compare this with the 5.3 hz example we see a much smaller rise around 5%. We have to extrapolate this answer, since it is off the scale of the graph. In other words at audio frequencies the heavy arm produces less bass boost.
You can also see that the damping applied has very little effect on the resultant gain as the lines are trending together. This means that even if we factor in a higher resonant amplitude for the heavy arm, we can see that while it alters things slightly, it has minimal effect.

There is some merit in a discussion of what happens at sub sonic frequencies but the arm with the lower multiplier (lighter arm) will face problems sooner as we decend below audible frequencies.

As explained earlier in this thread the maths quoted above is for a single pendulum. The calculations above are based on a singular pendulum. The calculations above do not take into account the fact that the ET2 arm & cartridge have multiple pendulum effects in the horizontal mode –
- the cartridge cantilever swings around the record pivoting at the stylus tip
- the cartridge cantilever swings around the cartridge at the suspension end
- the I beam

This is why when Bruce Thigpen measures the impact of coupling the I beam he can measure up to a 6-12db lift in the bass. The calculated numbers in the above post are are theoretical calculations for a single pendulum, which does not apply. No actual test results have been provided that support these numbers and conclusions.

Does this resonant peak really matter if it is below the audio spectrum ?

04-27-13: Ct0517
I usually hear only about audio designers trying to come below the audio spectrum – especially with a TT setup ?
That is what the conversations have been based on here as well ? 2hz – 6 or 7 hz. .

The fundamental resonance is created by the combination of the compliance/mass of the cartridge vs the effective mass of the arm.
Tonearm designers try to keep this as low as possible and minimize its amplitude.

The peak rise in bass response generated by the arm/cartridge does not rise and fall at one frequency. The peak resonance has a spread either side of that calculated peak resonant point.

Again I need to reiterate that Bruce has actually measured bass lifts of 6-12db when removing the decoupling.

Even if one ( wrongly ) assumed this resonance has no effect because it is out of the audio band, one would be wrong because the bass lift ( nasty peak resonance ) can impact tracking adversely.

This is why adding lead mass and removing the decoupling as advocated is wrong. Not only is it increasing inertia and side loads on the cartridge, it is also putting a lift in the bass frequency by removing the split resonance functionality that this arm uses to give a flat response. Adding lead mass and removing the decoupling will increase cantilever flex and tracking distortion.

does anyone know if there is a downloadable mounting template for the ET@. I have two of them, an I want to mount it on my custom Lenco, but I'd prefer not to start dirlling unless I know for sure what I am doing. I have dowloaded the manual, but it really doesnt give enough accurate info on mounting, mostly because you can buy a metal template.
anyone have any info?

Chris.

Good to read your findings on the gooseneck. They parallel what I heard when making the change here. You can expect more of the same when we find a way to bypass the o'rings in the manifold, along with a satisfying jump in dynamic contrast and low level detail.