Eminent Technology ET-2 Tonearm Owners

Richardkrebs
Also it is made from the same grade of aluminium as the spindle, 6061 T6. This to minimise the different material count in the arm loop.

A correction to my earlier post regarding the make up of the ET gooseneck. The ET armtube insert is aluminum as well. The joint itself is Carbon Fibre. Sorry for the error.
Both Richard's and Eminent Technology versions can be seen
here

Ok I think my eyes are doing funny things. I admit I saw and read a couple posts now in the last couple of weeks here - only to see them disappear? I have heard similar things about this phenomena on the MM thread. But there the posts never made it.

I know we are all big boys here and can handle whatever controversial topic comes up but maybe we have reached tolerance levels with the moderator? I think we still can have robust debate. Maybe we just need to be a little careful with some of the words we use. Just a thought.

Or maybe it is my eyes and I should switch to South African wines from Australian for a while? Good thing this hobby is based on hear and feel.

Cheers

Why your Brain Craves Music

A warning up front – the author does not care whether we use a spring or not. And his main music source is Spotify.

By Dr. Mercola

If you’re a music lover, you already know that turning on the tunes can help calm your nerves, make stress disappear, pump up your energy level during a workout, bring back old memories, as well as prompt countless other emotions too varied to list.

Even if you’re not a music aficionado, per se, there are compelling reasons why you may want to become one, which were recently revealed by a series of new research.

Music Prompts Numerous Brain Changes Linked to Emotions and Abstract Decision Making

When you listen to music, much more is happening in your body than simple auditory processing. Music triggers activity in the nucleus accumbens, a part of your brain that releases the feel-good chemical dopamine and is involved in forming expectations.

At the same time, the amygdala, which is involved in processing emotion, and the prefrontal cortex, which makes possible abstract decision-making, are also activated, according to new research published in the journal Science.1

Based on the brain activity in certain regions, especially the nucleus accumbens, captured by an fMRI imager while participants listened to music, the researchers could predict how much money the listeners were willing to spend on previously unheard music. As you might suspect, songs that triggered activity in the emotional and intellectual areas of the brain demanded a higher price.
Interestingly, the study’s lead author noted that your brain learns how to predict how different pieces of music will unfold using pattern recognition and prediction, skills that may have been key to our evolutionary progress. Time reported:2

“These predictions are culture-dependent and based on experience: someone raised on rock or Western classical music won’t be able to predict the course of an Indian raga, for example, and vice versa.

But if a piece develops in a way that’s both slightly novel and still in line with our brain’s prediction, we tend to like it a lot. And that, says [lead researcher] Salimpoor, ‘is because we’ve made a kind of intellectual conquest.’

Music may, in other words, tap into a brain mechanism that was key to our evolutionary progress. The ability to recognize patterns and generalize from experience, to predict what’s likely to happen in the future — in short, the ability to imagine — is something humans do far better than any other animals. It’s what allowed us (aided by the far less glamorous opposable thumb) to take over the world.”

To read more

Air Bearing Stiffness

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."

Richard - thanks for providing this info - the part that hits home with me.

“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 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.

This is truly outside of the box. Dover mentioned somewhere on this thread a while back that testing of the resonances with the ET2 seems to just pass through it ?

Dover - was this the same study? Maybe the test gear was not good enough to capture this info. I mean - its parameters setup for human hearing.

"Many times higher than the audio spectrum" I guess this explains why my dog does not start howling when I play music. Its beyond him as well. ...

Regarding leading note edge performance. My reference in my room are master tape dubs. No issues here with the air bearing.

Dover – I enjoyed your poem :^)
It reminded me of someone else on this thread whose moniker implies the test of time.
I am terrible at poems. I wrote one for a girl a long time ago and gave it to her.
She broke up with me the next day.
It left a bad feeling. Maybe I should try again...

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 ?

Some Gooseneck Impressions in my system/room.

First a reference point.

You can go listen to a group/band in the same location for two different days. They will sound different for each performance. No performance is the same. They are humans after all not robots. Sometimes you walk away from the performance with a smile on your face a lift in your step. Other days you are neutral; walk away thinking not about the performance but where you are headed next. This could be the result imo - of how your day went or maybe how the day went for those musicians. Did they gel or not ? I like my music to give me a lift, give me a smile. Its a stress reliever. When we add or change gear or tweak our gear it needs to go forward for us. This is a personal thing based on our own preferences. Its doesn’t always go forward as we all know. So.

In general a tighter sound and transients faster. More lively. Pace is quicker.

The Carbon Fibre (CF) gooseneck sounds a little plusher and velvety in comparison in my system. Bass notes last a little longer with the CF. This in turn depending on your setup can fill in the sound or smear the sound if too much bass – in the later case it makes the music sound slower for me.

The aluminum goose neck increases the clearness of the individual bass notes themselves; rather than a note mixing with another I now able to better hear the end of individual bass notes clearer. It was really good before - its just better now for me.

A bigger surprise to me. My room monitors were designed to be used in active mode with a Bass Alignment Filter (BAF). This allows the monitors to go down to 20 hz in a room that normally would not allow this much extension due to room constraints. I own a couple version of these BAF’s. This gooseneck tweak is a big enough tweak in my room that it allows me to better differentiate between the BAF’s and their engineering differences.

So many ways to tweak our sound from the source to speakers.
I am very happy with the sound and even more impressed with the quality of this piece.

Cheers

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.

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.

Dover wrote:

"This is nonsense Richard. Your comments that the air bearing is rigid defies physics. Have you heard of compressed air. You can get 2300l of air into a dive bottle with an internal volume of 11 litres. Try that with metal.

Why not try to compress 1 litre of metal into a 50ml can at audio frequencies. According to your thinking this is possible.

Do you get any of this?"

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.'

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?

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.

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

05-03-13: Ct0517
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.

Ct0517 – my point on adding mass being not desirable is in the context that Richardkrebs has advocated adding 30g of lead to the bearing tube and another 35g by removing the decoupling. Removing the decoupling increases the horizontal effective mass. This is a total of 65g of added horizontal effective mass. Far too much and from what I’ve heard when trialled.
Thigpens own words are to keep the horizontal effective mass as low as possible.
The “heavy” armtube that ET provide for MC’s is not massy.
Bruce advised me that

Bruce Thigpen
Without the wire harness the weights are respectively 13,17, and 19 ("heavy" version of the magnesium tube) grams.

So the heavy armtube is only 2-6g heavier than standard, not 60g as one has advocated. The link states “the new heavy version has over twice the wall thickness of the current magnesium arm tube to reduce the resonance levels in the arm tube “.
This is not to deal with the low compliance per se, it is to deal with the increased energy levels generated from having a low compliance that the armtube has to deal with, its about rigidity. This is similar to part of the rationale for having a decoupled counterweight. Thigpen says it allows him have a heavier and more rigid arm carrier/bearing tube and still keeping the horizontal effective mass as low as possible.

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.

Yes I should have used the words “standard ET2” agree with this. I was aware that if Bruce is advised what pump is to be to used he will provide a manifold tailored for that pump.

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. .

Excellent point on how adding mass can affect either vertical or horizontal effective masses separately or both depending on where it is added.
The issue that I have is the addition of some 60g to the horizontal mass.
Bruce’s testing and recommendations in his correspondence are to keep the horizontal mass as low as possible, or one will get an unnatural 6-12db lift in the bass, and increased tracking distortion.

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.

I have no issue with anyone wanting to do what they like with their system. As someone who has studied engineering at university and has a great respect for Thigpen’s design I take issue where misleading information has been provided or maths wrongly applied to support operating the ET2 outside of it’s design parameters and intended use.

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.

Absolutely agree. But see my leading edge notes below. I love the ET2 when set up properly, but there are some pivoted arms that can provide musical enjoyment as well.

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?

Chris – these are the words of the reviewer. I would not use the word boogie. My experience is that the Naim Aro, being a mechanically grounded unipivot bearing can reproduce the leading edge far crisper, cleaner and more extended the ET. An example would be percussive instruments. This is typical of well designed unipivots. I have a friend with 2 Graham Phantom’s mounted on a Micro Seiki RX5000 and I hear these same attributes. Even an inexpensive Hadcock can display these attributes – although it is not a true unipivot as the point sits in the apex of 3 balls.
I associate boogie more with the word rhythm and overall musical timing. In this context arm/cartridge matching plays a big part.
The Aro has a narrow operating window – my Dynavector Nova 13D and Denon 103D have better speed, timing and impact on the Aro than with the ET2. The Koetsu Black has more extension in the highs but does not boogie. Whilst it is quick on percussive, has great soundstage & transparency the bottom end timing is awry.
I get fantastic “boogie” with the ET2 when the ET is matched and tuned correctly with the right counterweight location and decoupling employed.The ET2 exhibits better timing and boogie when the horizontal mass is kept as low as possible to optimize groove tracking. If you watch the cantilever the timing goes awry when the cantilever is flexing around on an eccentric record. This is one of the big issues with adding 60g horizontal effective mass.
In my experience adding mass and removing the decoupling destroys the speed, timing and boogie factor.

With regard to springiness – there is an optimum air pressure for the mass at which an air bearing self centres. The design of the air bearing is critical to this, as is the surface area of the bearing and the mass and forces being supported.
http://demo.amplio.si//AmplioCMS2/UserFiles/File/29/theory.pdf

The main problem is that the cushion of air in the gap behaves like a spring. This means that, under dynamic conditions, the cartridge and tube assembly will move in various directions and the cartridge will not stay in the position of the cutter head but will be pulled along the groove and twisted due to the forcesmoving the cartridge in the grooves. Of course this also happens in pivoted arms, but due to differences in construction ie. loose bearings, vibration of bearings and other parts.
To practically avoid this effect we must use a stiff bearing, which automatically reacts to these external forces. Construction of a stiff airbearing is dependent on the air gap, air pressure and bearing surface. Higher air pressure means a stiffer bearing which can carry a heavier load. The same effect can be achieved by a small air gap between the moving parts of the bearing. In the best bearings the gap is limited to a construction of 10 microns. This is actually less than in most pivoted tonearms which have air slack in their bearings to move!!
A stiff bearing will not in itself stop the tonearm bearing from moving closer to one side of the bearing shaft when force is applied to one side. The bearing must be constructed in such a way that it is self-centering. That means, in practice, if force is applied to one end, the gap will decrease but a properly constructed bearing will respond to this by increasing airflow to the smaller gap, restoring the equilibrium.
In practice the gap stays the same if forces are not overloading the bearing and the cartridge position under dynamic conditions remains stable. If we apply force to one end of the bearing sleeve, we have the same problem. To have a self-centering effect along the axis as well as along the diameter of the rod, the airbearing must be properly designed.

This supports my view that if someone adds 60+g of mass to the ET2, not only would they have to increase the bearing stiffness, but would almost certainly have to redesign the bearing itself. This would still not negate the problems of increased distortion from running a higher horizontal effective mass and removing the decoupled counterweight on eccentric records.

Dover ....but there are some pivoted arms that can provide musical enjoyment as well.

You’re a real funny guy Dover. Did anybody ever tell you that?

I did not say I didn’t enjoy my pivot arms. I said they couldn’t go straight.....they need some help.

A couple of questions.

What make of pump and PSI did you use with your ET2, and did it (the pump) produce resonances and vibrations that forced you to use/build an external surge tank?

How long ago was it setup in your room?

My apologies in advance if this topic has already been covered in the thread. Too many posts to read thru.
Twenty years ago I made a oil damping trough for the then standard ET2, mounted on a Goldmund Studio. Mixed results, which could have been as much to do with opening the window to the performance of the Studio, as anything else. I put it in storage and forgot about it, only to find it again recently when looking for the aluminium goose neck for Chris.
So installed it on the current arm. Nice changes to the blackness of the background. The system is even quieter. As a result, it doesn't seem to extend dynamics upwards but downwards further into the low level detail. A very agreeable effect. Also greater presence and focus. It will be staying.
Is anyone else using an oil trough? If so what are your findings? I see from the ET website, that a very elegant design is offered.
bdpses

Andy Payor and Bruce Thigpen both disagree with adding mass.

Hi Dover,

Regarding the passage you quoted Andy Payor from Michael Fremer’s review on the Rockport 6000, while I have never read that review, but reading MF’s later reviews on the Rockport Sirius III and Kuzma Airline, gave me the impression that those comment were from MF himself rather than AP. Of course, AP might very well agree with that! Can you confirm?

About AP’s disagreement with adding mass, I would like to share some information. In the later, upgraded, models of the Rockport 6000, i.e. the 7000 and the arm on the Sirius III, AP chose to use heavier armtubes. I believe all 3 arms used the same air-bearing, and their armtube clamping systems are of the same (or very similar) total weight, but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

The heavier tapered armtubes (so the heavier moving assembly) on the later arms are said to be there for better bass performance, and minimize resonance. Granted, AP might have added the weight to help (add) more in the vertical, rather than the horizontal, moving mass, for better matching with mid/low compliance cartridges, but added weight he did! That may just be a matter of compromise!

The kong,
I am on a project at the moment and cant get back to the article but I believe it was a direct quote..I can confirm later if you like.
Meanwhile I see in the stereophile review of the Sirius arm: August 2000

The Sirius tonearm tube should be virtually inert, made of a constrained-layer-damped, 8-ply sandwich of carbon fiber and epoxy composite: four layers on each side of the damping material. Inside is a second tapered carbon-fiber tube, the space between the two filled with yet another damping material. The materials, construction, and aerospace pressure-laminating techniques create an armtube said to have the stiffness of steel, yet weighing only half as much as a comparable aluminum tube.

Another single billet of aluminum alloy is machined to make the bearing mount, tonearm clamp, and counterweight assembly. This is a big improvement over the design of the Series 6000 arm: the structure is said to be 20 times stiffer than before, yet no heavier.

This suggests the armtube is more rigid in the later models but lighter.
Fremer also paraphrases Payors comments on the ET as follows:

The air-bearing scheme—comprising a stationary bearing and a moving rail—invented by Eminent Technology's Bruce Thigpen and used on his tonearm as well as on the Maplenoll and Walker Audio turntables, comes closer to being truly "linear" because the bearing can be more highly pressurized. But the rail's large horizontal moving mass creates another set of problems. And a true linear tracker completely eliminates a pivoted arm's inherent tracking error and skating-force vectors.
All of which, to Payor, means that his arm is the best currently available, and the true state of the art.This is extremely important, as low moving mass is critical to the performance of a linear-tracking arm.

The use of English can be deceptive - large, heavy, higher mass. We see that Thigpens "heavy" armtube is only 2 gm higher. Payor may be referring to the physically large area of the arm/bearing tube or he may be referring to the actual mass, but it seems clear to me that he favours minimising the horizontal mass.

Furthermore, if you read the full article you will see that the bearing design and parameters and moving masses involved are mutually dependent as they are on all airbearing tonearms. I dont believe you can convert a Kuzma to a low mass or an ET2 to a high mass arm without redesigning the air bearing.
The resonances of the bearing itself can end up in conflict with the resonances generated by the arm/cartridge compliance.

This is where Richardkrebs continues to get the maths and physics wrong; there are multiple resonances involved, and the multiple resonances can quickly accumulate when overlapping - they are not a single spike at one frequency. This is what is happening with the ET2 when Bruce measures a 6-12db lift in the bass when coupling the counterweight - which effectively doubles the horizontal effective mass.

Richard re: damping trough. Thanks for bringing this up. I have completed my game of musical turntables, so I will revisit the damping trough now. It can get messy when moving an ET2 from one TT to the next with a trough of oil attached !
My main TT is completely changed from the last time I used the fluid so will try it again.

The fluid that Bruce uses in the trough is 8000 centistoke silicone fluid. I ordered some today from him along with the adhesive. Will post impressions later.

Richardkrebs - My apologies in advance if this topic has already been covered in the thread. Too many posts to read thru.

Richard - This thread is unfolding like a book. Very relevant ET2 information was discussed early on and throughout. I encourage a read through. If for no other reason than to understand and gain insight into why some members made the decisions they did.

Cheers

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325551242&openflup&67&4#67

Thekong - In the later, upgraded, models of the Rockport 6000, i.e. the 7000 and the arm on the Sirius III, AP chose to use heavier armtubes. I believe all 3 arms used the same air-bearing, and their armtube clamping systems are of the same (or very similar) total weight, but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

....Granted, AP might have added the weight to help (add) more in the vertical, rather than the horizontal, moving mass, for better matching with mid/low compliance cartridges, but added weight he did! That may just be a matter of compromise!

Thekong - thanks for sharing this info. Are you able play high compliance cartridges on your Rockport arm ? We know the heavier ET2 armtube affects the horizontal mass as well.

but the clamping system on the Sirius III are said to be 20 times stiffer due to the improved design.

I am assuming that this would limit the type of cartridges the Rockport Sirius III tonearm can now play as far as compliance is concerned ?

Cheers

Ct0517 - We know the heavier ET2 armtube affects the horizontal mass as well.

this was worded badly. This thread is too old to allow for corrections. I wanted to say the arm wand weight lighter or heavier, affects both the vertical and horizontal inertia at the same time. This is really important.

The 6000's relatively low vertical effective mass put its resonant frequency above the ideal 8-12Hz region with moving-coil cartridges of average weight and typically low compliance, causing the bass to begin rolling off prematurely. Andy Payor solved the problem on the System III Sirius arm—see my analogsourcereviews/review in August 2000—by adjusting the mass so that the arm's fundamental resonant frequency would be compatible with a wider range of cartridges.

Hi Dover,

Thank you for taking the time to check!

The above is a quote of MF from his review of the Kuzma Airline. By “adjusting the mass”, I am sure he meant “adding the mass”! Both the 6000 and 7000 also used carbon-fiber armtubes, but not as sophisticated as the one on the Sirius III.

But then, I agree with you that the weight increase of the armtube would definitely be less than 10g, and most likely in the 3-5g range.

Actually, by looking at the photos alone, it is hard to believe the massive armtube clamping system on the Sirius III has the same weight as that on the 6000. But, I have no reason to doubt AP’s claim!

Sirius III

6000

Hi Ct,

While I don’t have any really high compliance MM cartridges, I have no problem, “sound wise”, matching the 6000 to the relatively high compliance VDH Colibri! Yes, the combo is relatively lean in the bass/mid bass, but I consider it the character of the cartridge.

Now, I say “sound wise”, because while the sound was fine, I (and also my friend who had the same combo) found the Colibri’s cantilever slightly off-centered after a period of time. This I took it as the fragile nature of the Colibri’s design.

MF repeatedly stated the 6000 was relatively bass shy compared to the Sirius III and Kuzma Airline; I believe a major reason was that the stock pump just couldn’t supply enough pressure. As I mentioned before, I believe the 6000, 7000 and Sirius III shared the same bearing, but the 6000’s stock pump (probably due to cost constrains) could only supply a max pressure of around 11 psi, and without any surge tank. Once I upgraded it to a June Air compressor with integral surge tank, plus additional pressure regulators, supplying 34psi to the 6000, its bass weight and definition improved considerably! As I understand from the Rockport agent, the Sirius III’s arm also uses around 32-35 psi!

The kong,

thanks, pictures are interesting - the stiffness around the arm connection is obvious. The 6000 does look quite flimsy, whereas the Sirius has a tapered armtube to a larger armtube clamp. The energy control should be much better.
Also interesting are the similarities to the ET - the tapered armtube for MC's and the use of a relatively small counterweight quite a long way away from the bearing. Having less mass in the counterweight further out lowers the horizontal effective mass ( clearly a design goal for Payor ) but increases the vertical effective mass ( good for low compliance MC's ). This is exactly the same strategy employed in the ET.
Re the van den hul bent cantilever - I ran a Shure V15Vmr on the ET2 for about 10 years whilst I had a hiatus from audio in the 90's. The Shure is around 20 yrs old, still has the original cantilever & stylus, has only ever been used on the ET2 and the cantilever is as straight as a die; this I think a testament to the ET2's relative light mass and decoupled cantilever and of course the electromagnetic damping discussed earlier in this thread would have helped as well.

Thanks for that info Thekong and Dover.

Thekong – something doesn’t look right to me with that Sirius III pic ?

Looking at the air tube wiring – how does that tonearm get past the 2nd track?

Isn’t the air tube pushing back at the arm as it makes its way across ? Is there that much friction in the slider to not be affected?

If that was an ET2 just the wires alone in that position would cause it not to work. Sorry for all the questions.

Definitely a very different design. Thanks for the pics.

So the air that comes into the arm is going into to a smaller diameter air tube. This is compressing the air and I assume making higher pressure.
Cheers

Ct,

You have sharp eyes, yes the owner of that Sirius III was complaining on Audiogon that the arm couldn’t track more than 3 cuts into the LP. There are actually 2 black hosts in that photo, one for the air, and one for the signal wire. I believe it was just set up wrongly; it should be like the photo of the 6000, with the signal wire host pull back as much as possible, and both the air-host and signal wire arranged into a hanging n shape!

Dover,

My 6000 came with 4 counterweights of different sizes to match with different cartridges!

Regarding the off-centered cantilever of the VDH, I believe, while great sounding, it is just a very fragile design, and probably not really fit for air-bearing arm including the ET2. After having it fixed, my friend has used it on both the SME V and Graham Phantom with no problem!

I will try to weight the sliding assemble of the 6000 this weekend and report back!

Thekong.

It will be interesting to read about your findings.

Do you have the horizontal effective mass figure for the 6000? Can you please post this if you have it.
My experience with adding weight is that you should be targeting a horiz resonance of 5-6 hz. The formula on the ET site can be used to calculate this and hence how much weight to add. You may need to concurrently adjust the vert mass as well. This I did with the lead shim inside the headshell.
From the photo you posted, it looks like the 6000 has a damping trough? Until recently I have been using the dressing of the lead out wires for damping. This works but goes out all the time, requiring constant tweeking. The oil trough is much better, being consistent and I would now consider it to be manditory in a heavy arm.
thanks

Thekong ....the owner of that Sirius III was complaining on Audiogon that the arm couldn’t track more than 3 cuts into the LP.....

Hi Thekong – thx for that info.

Well imo whatever it was able to play ...it would have been a subpar performance from the start of the first track anyway from what is capable. Hopefully the wires have since been fixed up.

What I don’t get...how does a high profile, statement item like that get into that condition; especially when the wires and also the air tubing in this case represent an Achilles Heel if not set up properly. Not a question per say just a little dis-belief on my part considering the dollars involved.
Cheers

Hi Richard,

Yes, the 6000, and all other Rockport arms, has damping trough. The “paddle” is fixed, so unlike the Walker, you have to adjust the amount of damping oil you put in!

However, I and a couple of my friends who had the 6000, prefer it without damping; it just sounds more lively, or more PRAT! I may revisit this topic later!

I have measured the weight of the Rockport 6000 in the weekend, and to my surprise, the whole moving assembly weighted in at 90g (including the A90 at 8g, and a spacer at 2.5g). I am using the lightest counterweight out of the 4, and the heaviest one would add another 15g!

With the figure about, it is hard to believe the moving mass of the Airline is only around 100g considering how massive it is compared to the 6000!

Is there a way to tell if I have a high pressure manifold on my ET2? Some sort of marking on the manifold, or a different size? I have a couple of different pumps, but dont want to put on a higher pressure if its going to damage something

05-13-13: Manitunc
Is there a way to tell if I have a high pressure manifold on my ET2? Some sort of marking on the manifold, or a different size? I have a couple of different pumps, but dont want to put on a higher pressure if its going to damage something.

Hi Manitunc

***********************************************
ET 2.0 spindle is about 5/8 inch.

ET 2.5 spindle is about ¾ inch.
************************************************

from my 05/03/2013 post.

One way to tell if its a HP manifold.

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.

Another way to tell.

Bruce built the manifolds for different pressures based on customer specs. If somebody bought their ET2 or ET 2.5 used and did not know the seller they don’t know what the pressure is – unless it came with the pump.

In order for the air bearing to become rigid it needs to be run at least at the PSI designed by Bruce for that specific manifold. Going over that pressure may produce sonic benefits in a persons room – IMO - this is subjective thing; based on our own room/gear synergies - just like speaker wire and interconnects – hah hah. How do you like that comment ? if a higher pressure works - great.

The original ET2’s were around 3 - 3.5 psi with the Takatsuki SPP-6GA pump.

The WISA pumps were 5-7 psi.

So Manitunc I suggest you try your arm first with the original low pressure pump first if you have it – SPP-6GA.

If it works its the original ET2 manifold. If it needs a higher pressure to work you have a HP manifold.

This applies to both ET 2.0 and ET 2.5’s.

This can be confirmed by contacting BT.

You can’t hurt it with higher PSI – in fact raising the pressure in increments will let you fix any leaks your arm may have if it has been sitting around for 10 years. You will blow off the air hose if anything.

Since we are talking about pumps - I will post how I test my ET2 pumps.

Cheers

Manitunc – just a note on my last post.

If it works its the original ET2 manifold. If it needs a higher pressure to work you have a HP manifold.

If we are talking about an older ET2 arm it may need more pressure because of it being dirty. Its a good idea to clean inside the manifold first. Slide out the spindle and use a toothbrush with alcohol and scrub the inside of the manifold. See page 40 of manual. This is an easy enough procedure and highly recommended for anyone buying a used ET2 with no history.

Cheers

Thekong.
It should be no surprise that the arm weighs in at that figure or even higher with the heavier counterweights. It is neccessary for it to perform well with low compliance carts. This provided that appropriate damping is applied. Lead out wires, air tube, and maybe an oil trough.
An obsessive designer like Andy Payor would have taken this weight factor into consideration.
I agree, it would seem that the Kuzma is indeed a lot heavier, based on its appearance. That said, maybe it uses carbon fibre and other weight saving techniques?

05-13-13: Richardkrebs
Thekong.
It should be no surprise that the arm weighs in at that figure or even higher with the heavier counterweights. It is neccessary for it to perform well with low compliance carts.

This is not correct with respect to the ET2. In my experience adding mass to the ET2 with low compliance cartridges reduces the speed, articulation, transparency and harmonic structure of the music.
Increasing mass with the ET2 also increases tracking distortion and can result in a bass hump of 6-12db by loading up the cartridge with high mass.

A quote direct from Bruce Thigpen

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

Quote from ET2 Manual – Bruce Thigpen

P29
It is desirable in most cases ( low to medium compliance cartridges 5x10 dynes/cm – 20x10 dynes/cm ) to use the minimum number of weights, far out on the cantilever stem. This decreases the horizontal inertia of the tonearm while increasing its vertical inertia.

Adding mass to the ET2 increases the inertia to lateral movement and on eccentric records will result in increased cantilever flex and distortion.
Any excessive cantilever deflection in a moving coil will result in phase anomalies as the coils attached to the cantilever are driven into a position where the response becomes non linear. This is what Bruce Thigpen is saying.

Furthermore, with higher mass, once the arm starts moving, the lateral movement is undamped. Cartridge overshoot and uncontrolled cantilever flex are inevitable. This explains why when Richardkrebs added fluid damping the sound appeared to be better controlled or in his words had “greater presence and focus”.
This is because the addition of lead mass and removal of the decoupling mechanism from the I Beam in his ET2 pushes the horizontal mass too high and the cartridge cantilever motion goes out of control. He would be better off reducing the horizontal effective mass by removing the lead he added to his arm and putting back the decoupling in the I Beam that he removed.

If you go to the Eminent Technology website and read the ET1 manual (that’s the arm that precedes the ET2) you will discover that the ET2 was a design decision to move away from the high mass/fixed counterweight model utilized in the design of the ET1 to the low mass decoupled counterweight model utilized in the ET2. These new design considerations embodied in the ET2 resulted in substantive improvements in the quality of sound reproduction.

The decoupled I-beam methodology employed by Bruce Thigpen in the ET2 is designed to minimize horizontal mass and ensure that the resonance of the I-beam and counterweight remains below the horizontal resonance of the arm so that the 2 resonances (arm and beam) do not couple together to produce a large peak resonance in the bass.

The horizontal effective mass for a linear air bearing arm is the sum of the mass of the bits that move sideways.
The ET2 reduces this mass by decoupling the counterweight. We all clearly understand this design feature. The benefit of this approach is to reduce the amplitude of Fr
The bearing design makes no difference to the effective mass or the resultant Fr. There is nothing particularly unique about the ET2 bearing. The cartridge still has to push this mass sideways. Either a relatively low mass with the ET2 or heavier with a Rockport , Kuzma, Walker or Krebs arms. In an undamped system with a fixed counterweight we see a large rise in amplitude at resonance. This is easy to control with damping. For a good discussion on this see CT0517's post on 01-12-12
Open the attachment and read pages 18-19 and 24-26.
The graph on page 25 shows how this peak is completely removed by adding an oil through. The subsonic peak has gone and provided Fr is low enough, so has its effect on the audio spectrum. In this paper Bruce talks about the effect being noticeable at 3x Fr. Way back in this thread I talked about the effect of resonance being present at up to 6x Fr. We use this safety factor in our designs in my business.
It is this effect that led me to fix the counterweight. With a stiff cartridge; the only way to get Fr low enough to avoid interaction with audio frequencies was to make the arm heavier. The Fr of my arm/cart is 5.2 Hz. Thekong's setup is a little under 5hz. In Fremer's review of the Kuzma he set it up with a Fr of 5 hz. This is no coincidence , we all set up our systems with effectively the same Fr, safely 4x below the audio spectrum. My point is that the Fr needs to be around 5-6 hz. To avoid this interaction. With a high compliance cart this target is achievable with a standard ET2, it cannot be achieved with a low compliance cart. At least 3 respected designers agree with me.

In past I have damped the resonant peak by adjusting the air pressure and deliberately dressing the lead out wires to damp horizontal movement. This method is fussy and not particularly robust. Adding the oil trough has solved these problems and allowed me to push the pressure back up. 17 psi seems optimum in my rig.

There have been concerns raised about the extra weight I have added pushing the bearing outside it's design spec.
I am using the original wand less its heat shrink wrap plus a lead headshell insert. Say the same weight. I am using an aluminum goose neck which eliminates one cap screw and the short lifter arm. I have also eliminated the male wiring plug and used a lighter grub screw instead of a cap screw for the gooseneck wand clamp. Say same weight.
I have fixed the counterweight and eliminated the I beam the brass threaded weight, several cap screws and the locking slider assembly. Say same weight.
My counterweight is 32 grams.
I have added 30 grams of lead inside the spindle in the center of working travel, such that it does not leave the bearing sleeve when tracking modulated grooves.
The ET2 can be optioned with the heavier magnesium wand. 8 gms heavier.
It comes with up to 40 gms of counterweight. 8 gms heavier.
In terms of bearing load carrying capability I have added 30 gm to a lightly configured ET2. If we option it with the magnesium and use all the supplied weights my weight adder is now reduced to 14 grams.
I use a Shelter Harmony at 9 grams. There are cartridges in the 16-17 gm range. If one of these was used the my weight adder shrinks to around 6 gms. It would be inconceivable that Bruce would design a bearing that could not take this small additional weight.

Richardkrebs - For a good discussion on this see CT0517's post on 01-12-12
Open the attachment and read pages 18-19 and 24-26. The graph on page 25 shows how this peak is completely removed by adding an oil through.

ET2 damping trough

Bruce why didn’t you number the pages ?!!!

Richardkrebs- There is nothing particularly unique about the ET2 bearing.

Richard – what is this statement based on?

Please note this observation from Thekong who has compared it to the Rockport.

03-13-13: Thekong

Hi Ct,

However, there is one interesting point that I still can’t understand. When moving the arm in and out by hand, the feeling of the ET is smoother (or I should say requires less force) than the Rockport! While I don't have the spec. of the 2 bearings, I have always assumed that the Rockport has a tighter tolerance / air gap. This can be shown when trying to move the arms without the air supply. While you can still move the ET quite easily, a lot more force is required for the Rockport in this condition.

If the air is off on my Kuzma Airline it is quite hard to move the tonearm.
Will be joining the ET owners club.
The ET arm that I purchased should be in my sweaty hands by the end of the week.

Chris
The statement about the ET2 bearing was in relation to it being subject to the same rules regarding resonance , load carrying capability dynamic stiffness etc.
Any problems due to higher mass will manifest themselves in linear air bearing designs regardless of the manufacturer. There may be variations in degree, but they will be there.
In other words if my heavy ET has problems with cantilever flex, bass boost, phase shift and so on; so do the other heavy arms. Rockport, Walker, Kuzma. This because the horizontal effective mass is solely determined by the total weight that is moved sideways at the frequency of interest, since all of these designs are virtually frictionless.
The level of damping of course changes all this. Enter the oil trough.

The difference observed between the ET2 and the Rockport could be due to the designed operating pressure and the bearing clearance. Haven't seen a Rockport in person so this is a guess.

Hi Rugyboogie,
Can the moving assembly on the Airline be taken out easily? If it can, and it is not too much trouble, I would really appreciate if you could weight it to confirm whether it is really only around 100g.

Hi Ct,
Yes, I still don't understand why the ET bearing feels smoother (to the hand) as compared to the Rockport when both are having the air-supply. I would assume both of them are virtually friction free under this condition! Maybe Rugyboogie can share with us his finding when he got his ET!

05-14-13: Richardkrebs
The cartridge still has to push this mass sideways. Either a relatively low mass with the ET2 or heavier with a Rockport , Kuzma, Walker or Krebs arms. In an undamped system with a fixed counterweight we see a large rise in amplitude at resonance. This is easy to control with damping.

The adding of lead mass will increase distortion due to the higher inertia of the arm. Basically you have added a peak resonance in the bass, then tried to tame it by adding damping. Both the added mass and fluid damping will increase inertia, and compromise the ability of the cartridge to track the grooves accurately. On an eccentric record this will be even worse. The Krebs arm has some 65g of horizontal effective mass added - an increase of inertia close to 300%. This increases cantilver flex and distortion as per Bruce Thigpens commentary.

05-14-13: Richardkrebs
With a stiff cartridge; the only way to get Fr low enough to avoid interaction with audio frequencies was to make the arm heavier. The Fr of my arm/cart is 5.2 Hz.

This is not true. Most tonearm designers target a FR of around 8-12hz. This is based on an assumption that most systems dont produce much response below 20hz and footfalls are in the zone of around 2-3hz, dangerously close to your 5hz.
Secondly, the increased distortion from the added inertia of the arm resulting from the increased horizontal effective mass certainly impacts the audio frequencies.
The phase anomalies from the increased distortion on the cantilever can be heard quite clearly in a system that is reasonably transparent and quick. Furthermore the peak resonance at 2-5hz that you quote can invoke instability in tracking, its the same as walking past a turntable on loose floorboards.

05-14-13: Richardkrebs
In past I have damped the resonant peak by adjusting the air pressure and deliberately dressing the lead out wires to damp horizontal movement. This method is fussy and not particularly robust.

Basically what you are saying here is that you like the sound of the ET2 with additional drag inhibiting the free movement of the arm to track the grooves. In my experience this slugs the sound. Other users have found improvements by removing this drag - they have removed their fluid damping and replaced it with electromagnetic damping which has the benefit of not inhibiting movement until the movement happens.

05-14-13: Richardkrebs
My counterweight is 32 grams.
I have added 30 grams of lead inside the spindle in the center of working travel, such that it does not leave the bearing sleeve when tracking modulated grooves.
The ET2 can be optioned with the heavier magnesium wand. 8 gms heavier.
It comes with up to 40 gms of counterweight. 8 gms heavier.
In terms of bearing load carrying capability I have added 30 gm to a lightly configured ET2. If we option it with the magnesium and use all the supplied weights my weight adder is now reduced to 14 grams.

Your mathematics is incorrect :
The bearing spindle without arm/counterweight is 14g
The aluminium arm is 11g
The CF arm is 17g
The Magnesium arm is 19g

So the total horizontal effective mass of your 9gm cartridge on a standard ET2 arm with a 32gm decoupled counterweight is:
9g(cart)+11g(arm)+14g(bearing spindle)=34gm

The total horizontal effective mass of your 9gm cartridge on your altered ET2 "Krebs arm" with 30g of lead added and the 32gm counterweight coupled is:
9g(cart)+11g(arm)+14g(bearing spindle)+30g(lead that you added to the spindle)+32g(counterweight that the cartridge now sees because you removed the decoupling)=96g

Therefore you have increased the horizontal effective mass from 34gm to 96gm, an increase of 62g.

I cannot see how you get to 6gm in your maths.

Coupling the 32g counterweight adds 32g to the horizontal effective mass.
Adding 30g of lead to the spindle increases the horizontal mass by 30g, even when placed inside the bearing.

05-14-13: Richardkrebs
If we option it with the magnesium and use all the supplied weights my weight adder is now reduced to 14 grams.

This is another area where the underlying assumptions are misunderstood. Bruce's recommendations documented in the ET2 manual on low compliance cartridges is carry as little weight as possible as far out on the I Beam as possible. This keeps the horizontal effective mass low but increases the vertical effective mass. It is not recommended to load the I Beam with all the counterweights if one can shift the counterweights further out.