Eminent Technology ET-2 Tonearm Owners

Hi theKong – answer to your question from Bruce. Thanks for that info as well Dover. Acoustats ? won't go there.

03-27-13: Thekong
As we have been discussing the pros and cons of the decoupled counterweight on the ET,
I have this question on my mind (admittedly a non-technical one) for a long time!

The ET uses leaf springs to decouple the counterweight so the arm doesn’t “see” the additional weight!
To my thinking, this can only be possible if the counterweight actually doesn’t move during the initial movement (milliseconds?) of the arm,
due to the compliance of the leaf spring.
Then, after the arm has moved for a certain range, the counterweight would need to start “rebounding” to follow the arm.

If that is true, then would it create some delayed effect that could be detrimental to the tracking?

Or is my reasoning totally false?
Thekong (Threads | Answers | This Thread)

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Answer from Bruce.

Chris,

The counterweight is decoupled in the horizontal plane so it only affects lateral motion of the tonearm. The counterweight always moves if the spindle is moving, it does not move at the same rate, the time constant is about 300 milliseconds. 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. The motion of the weight is damped so that it has a low "Q" resonance with a rise in response of about 3-4dB at 3hz and 2dB at 10-11Hz, these frequencies do not coincide with the vertical resonance.
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, amplification chain, and especially in the speakers woofer at a few Hz. I hope this helps.

brucet

Boy I wish I had someone like Bruce for when I go into these board meetings trying to sell services to CEO’s and CFO’s. You know the ones where they bring their own in house techies to the meetings to ask questions.

Cheers

Chris, your diligent follow up with Bruce Thigpen is much appreciated:

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,

Bruce Thigpen’s contribution affirm my statements over the past 7-8 weeks that Richardkrebs fixation with adding lead mass to the arm and coupling the I beam will increase distortion, affect tracking and produce an unnatural bass lift in response. My own analysis has long been based on a thorough understanding of the design principles and physics involved.

It is disappointing that those who disagree, and clearly do not grasp the principles involved in this arm, have resorted to denial and personal attacks

03-04-13: Richardkrebs
Dover
Your scaremongering

03-17-13: Richardkrebs
Dover.
Hasn't this discussion run its course.

03-18-13: John47
Mr Dover’s bombastic contentions.

03-21-13: John47
Put on your knitwear cardy so don't catch a cold, your thick lensed glasses so you don't fall, then pop out and replenish your Prozac.

03-23-13: Gnnett
As a New Zealander I would like to apologies for the behavior of Dover. It is a narrow country and this breeds narrow mindedness.

All too often denial and personal abuse is the last refuge of the desperate.

Sadly those posters who are fixated with the idea of adding lead mass and removing the decoupling will continue to deny the science and exhaustive testing and measurements that underpin Bruce Thigpen’s design.

If they prefer the sound of the arm set up incorrectly, there are clearly fundamental flaws in their system and they should look at the rest of their components and set up. This includes the environment in which they are listening.

03-04-13: Richardkrebs
Dover
I am the only person here who can speak with any authority on the subject.

Richardkrebs, the ET2 is a brilliant design and deserves to be treated with respect.

Frogman/theKong, others – regarding lowering the position of the lead weights.

Based on my own experiences, positioning the lead to be lower is not something imo, that any ET2, ET 2.5 owner is going to do naturally or instinctively. The reason being it is not as ergonomic. When you try it you will see it is easy to touch/scrap the plinth/armboard with the end of the I Beam, when you lift the arm at the end of a record. That is, if you have developed a habit like I have, of lifting the arm tube higher than required in protection of the stylus. This was an easy habit to break.

I talked to Bruce about it and he said multiple parameters get changed when doing this and that in general he's for an adjustment that results in an increase in VTF requiring the lead being moved further out on the I Beam. But we need to try it out in our rooms/gear. Look forward to both of your impressions when you get a chance to try it. I’ve had two positive listening sessions with now.
Cheers

Dover...your diligent follow up with Bruce Thigpen is much appreciated

Dover you’re welcome. I like to publish information for thought especially when it comes from a Subject Matter Expert (SME). Someone who by the way takes an interest in our activities and findings, and continues to experiment on his own.

The info was not meant however to trigger any type of civil unrest with the NZ audio club.

Fwiw - I have heard many stories of civil unrest from my Grandma and parents.

In Canada I have seen civil unrest twice when Quebec decided to separate.

Democracy prevailed.

If democratic polls were held today I am not sure but I think the vote would be 2 – 2 or 3 – 1 against you.

Good thing this is a hobby ?

Chris - thanks - no war down here.
My motivation is to help people set their systems up correctly and learn more. We all learn from shared experiences. The debate over the past 7-8 weeks could have been much shorter had it not been inundated with junk science.

Richardkrebs, claims to be an authority, yet all the way through been belligerently dismissive of Bruce's recommended set up procedures and of the design principles that underpin this arm. Many of his arguments put forward were simply nonsense.

Everything I have said has since been verified by Bruce Thigpen's recent communications. The addition of lead mass and removal of the decoupling of the I beam will load the cantilever, increase distortion, and deliver a bloated bass response.

Would you have rather everyone who read this thread ignore Bruce's advice - add lead mass and bolt up their I beams as was suggested ad infinitum?
That, along with much uninformed comment, is an affront to the time and dedication that Bruce has put into this product. It is impossible not to have robust debate when basic scientific principles continue to be denied.