Eminent Technology ET-2 Tonearm Owners

My view on a stereo system is that it is just a machine. Actually lots of machines chained together to give an output based on inputs. As such it is logical and the output is predictable provided we have sufficient understanding of the machine. ( none of us have sufficient understanding )
What we are talking about here is a small part of the machine. The coupling, decoupling of a counterweight on a linear arm.

Frogman and Dover say that they prefer a loose connenction and one leaf spring.
Chris says that triple springs produce a sound that is too lean.
Rockport, Walker, Kuzma and I say that there should be no spring at all.
I believe ALL of the above statements as I think that they are actually saying the same thing along a continuum.
It all depends upon the voicing of your system and our biases, and we all have biases.
Also an improvement can actually sound worse as it can expose more clearly problems elsewhere in the machine chain. Sometimes when we open the window wider, we do not like what we see. We then need to work on the new "view" to correct a previously unseen problem. It does not mean that the original change was wrong
I have said that I don't think that it is a good idea to have a mass attached to two dissimilar springs who's resonances are in the same neighbourhood. The transmissibility graph I posted shows the potential nasty consequences of this. At least a 6 x seperation of the two resonant frequencies would a target.
Using one spring lightly coupled to the spindle pushes the resonant frequency down below the arms core resonance. This is good. (As Frogman points out, there may be other factors at play here with the loose screws.) Double or triple springs push the resonant frequency above the core resonance which is also good.
We have to be carefull when using stiffer springs that we don't move too close to the audio spectrum, since the same transmissibility graph data will bite us. We also have to be carefull that we do not go to low with lite springs since we get close to eccentricity frequencies again with possible nasty consequences. So what if we pushed the resonant frequency up above the audio spectrum. We have no risk of any of the issues I raise here.
My early fixed counterweight designs resonated somewhere in the midrange. It was easy to hear adding a nice, but not accurate bloom to voice and midrange instrumemts. If my system was not already "full" in this range I may have stopped experimenting, thinking that the arm was acurate. Increasing its rigidity more, pushed the resonance above the frequency of audibility. This is desirable and is the final logical progression to the tests that have been listed in this thread.

Gnnett. Do you live in AKL? It would be nice to meet. You can contact me directly via my web page if you wish.

Richardkrebs:
Yet again I have to address your gross assumptions and misunderstanding of the principles of the ET.

Richardkrebs
Frogman and Dover say that they prefer a loose connenction and one leaf spring. Chris says that triple springs produce a sound that is too lean.
Rockport, Walker, Kuzma and I say that there should be no spring at all.
I believe ALL of the above statements as I think that they are actually saying the same thing along a continuum.
It all depends upon the voicing of your system and our biases, and we all have biases.

This is absolute rubbish. You are implying that the decoupling and non-decoupling are both valid, when they are not. With the ET2, the outcomes are entirely different and Bruce Thigpen has tested and measured these. The decoupled methodology employed by Bruce Thigpen is designed to minimize horizontal inertia and ensure the resonance of the I beam and counterweight remains below the horizontal resonance of the arm. The rigid coupling of the I beam and counterweight that you advocate is contrary to these stated design goals. Your comment about voicing the system to biases is as presumptuous as it is incorrect. An experienced listener can hear changes in transient speed and accuracy of timbre and timing irrespective of the system. That is how a system should be tuned.

Richardkrebs
Double or triple springs push the resonant frequency above the core resonance which is also good.

Your statement contradicts research and testing by Bruce Thigpen, and I quote the following email from Bruce Thigpen published above:

Bruce Thigpen
Chris,
You always want the horizontal natural frequency of the counterweight to be less than the cartridge/arm resonance, this is the case 98% of the time.
The natural frequency of the I-beam/leaf spring depends on the thickness of the spring, the amount of weight, and where the weight is on the beam. The natural frequency goes down as the weight moves further out on the beam which is where we want it to be.
brucet

Richard, clearly you have not done any testing to support your guesswork, otherwise you would have found that 98% of the time you are wrong.
If you bothered to read the manual you would see that the double spring is for low compliance cartridges and should be used with the minimum counterweight pushed further out on the I beam to position the resonance of the I beam and counterweight BELOW the horizontal resonance of the arm.

Richardkrebs
I have said that I don't think that it is a good idea to have a mass attached to two dissimilar springs who's resonances are in the same neighbourhood.

Again, if you bothered to read the manual and Bruce Thigpen’s website, the decoupled counterweight is designed precisely to achieve this. Furthermore on Bruce’s website he has provided extensive test results proving this.

Richardkrebs
The transmissibility graph I posted shows the potential nasty consequences of this.

I have already explained to you in great length that the mathematical model you refer to, "harmonic oscillators", which you pulled out of wikipedia, does not apply. Let me help you. Read my post of 03-14-13, the first sentence begins

Dover
Richardkrebs
OK now I understand where you are going wrong in your thinking.

Richardkrebs
At least a 6 x seperation of the two resonant frequencies would a target.

Where did you pluck this number from? Why 6 times? Please don't use an incorrect mathematical model again when you attempt to explain.

Richardkrebs
We also have to be carefull that we do not go to low with lite springs since we get close to eccentricity frequencies again with possible nasty consequences.

Bruce has completed extensive testing and provided clear guidelines on the use of the light spring. He has calculated the resonances and provided extensive guidance. What testing have you done, or is this purely speculative guesswork on your part yet again.

Richardkrebs
My early fixed counterweight designs resonated somewhere in the midrange.
Increasing its rigidity more, pushed the resonance above the frequency of audibility.

Have you tested this? What resonant frequency did you measure?
More guesswork?

Richardkrebs
This is desirable and is the final logical progression to the tests that have been listed in this thread.

You persist in arguing your unfounded case for fixing the counterweight.

Arrant nonsense.

To remind readers I repeat:
The decoupled methodology employed by Bruce Thigpen is designed to minimize horizontal inertia and ensure the resonance of the I beam and counterweight remains below the horizontal resonance of the arm. The rigid coupling of the I beam and counterweight that you advocate is contrary to these stated design goals.
Once again, we go round the block for the umpteenth time.

Bruce Thigpen has calculated, tested and measured precisely the resonances of the decoupled I beam and counterweight with a wide variety of cartridges from low to medium to high compliance to determine the level of decoupling required to optimize the cartridges performance.

How many times before you get that decoupling is an integral part of the ET2 design and how the arm is engineered to optimize performance. You are clearly out of your depth. You persist in misapplying physics and just don’t seem to be able to comprehend the design. Do you run your car on 3 wheels?

You have resorted to implying that readers who have tried removing the decoupling and found it to be detrimental are either fixing up defects in their system or have biases. That is an arrogant assumption, and reflects poorly of your estimation of the contributors to this thread.

Richardkrebs
My view on a stereo system is that it is just a machine. Actually lots of machines chained together to give an output based on inputs. As such it is logical and the output is predictable provided we have sufficient understanding of the machine. ( none of us have sufficient understanding )

Richard - from what I have learned about you, IMO you are one of the few in this hobby that can build and repair your own amps, preamps and TT’s, etc... Fair statement?

As an amateur hobbyist I have my ears and memories of trial and error experiences. I agree with you that the actions and reactions that are happening are more predictable to a degree with some knowledge gained. I also agree that none of us have sufficient understanding. If anyone really did word would get around, and there would be a long audiophile line up at the persons door asking for help.

Now consider this perspective. I refer to the Quad 57 speaker again just as an example.

I have tried multiple amps with them (SS and Tube) out of curiosity; then one day after more research I discovered that Roger Modjeski designed his RM 10 amplifier around their specific needs. I already had his larger RM9 amp which I tried with them briefly, but was concerned about damaging them. Anyway cutting to the result - I now power them with an RM10 and could not be happier. So what I think I have based on what I hear is an amp whose outputs meet the specific needs of this unique speaker. There is a harmony and effortless sound that can be heard. Now consider this.

I have placed these 57’s in 4 different rooms with identical gear in front of the Rm10 amp and the 57’s. One room had hardwood floors, one was tiled, 2 were carpeted. Some rooms had drapes, other s only drywall and some pictures. One had wood panelling on one side. Their dimensions all varied and two of them opened up into other rooms.

Four different music perspectives resulted in the sounds as far as the music presentation goes. This was all with the same CD player. Now add in vinyl with all its variables to the mix...... The stereo system is a slave to the space/room -imo.

Just to be clear here to the readers regarding my impressions I have given. We have been discussing refinements and tweaking for the ET2. In the last 10 years I have owned an ET2 and then added a ET 2.5. In stock form as designed – out of the box this tonearm remains my reference.
And fwiw - The greatest sonic bump with the ET2 came for me, when I introduced air delivery with no (very little) resonance (at the pump) and 19 psi was achieved. The ET2 tonearm setup so far for me has been 40% actual tonearm setup fine tuning, and 60% air delivery tweaking. I am sure with the continued info from this thread it will become 50 – 50 soon.
Cheers

Dover.
:Yes the outcomes are entirely different if the counterweight is fixed....so.
:We have established that it will not be the end of the world for the cartridge if the horizontal mass is increased, this by reference to other arms that are heavy.
:Countary to stated design goals yes.....so.
:While BT designed the cw arm to swing at frequencies below the core arm frequency, it does not neccesariy prove that using 2 springs will result in that criteria being met. It is almost certain that the use of three springs, as Chris did will push the frequency above core.
:I know that BT designed the arm to have the two spring systems, Cart and Counterweight. I just don't think that it is a good idea because they talk to eachother. Has anyone thought about why the CW spring(s) and their damping are so fussy to set up?
:Yes I pulled the resonance graph and math from the net. This because it explains the effects more clearly than the literature we regularly refer to here at my work. Those readers that understand the math will know why I chose a 6 times multiplier.
:My prime reason for fixing the counterweight is to restore the full bass drive. You have in an earlier post talked about not needing response below 30hz and that response in this region can be problematic, or words to that effect. I do want response in that range and yes it can be difficult to sort this area but with effort it can be done and the results are most rewarding.

:We are all biased, it is astonishingly arrogant to suggest that you are not.

Chris.
Agree the room is critical, same for the air feed.

ET 2.0 spindle versus ET 2.5 spindle

I am focusing on the spindle /counterweight. I have some info to share.

It can be difficult from pictures telling the differences between the ET 2.0 and 2.5.

This makes it easier. Pictured is the

ET 2.5 spindle

Significant differences in weight and diameter.
19 gms ET 2.5 versus 11 gms ET 2.0.

Chris,

About 19 grams with the aluminum inserts which are machined from bar stock. The 2.5 tubing has about the same wall thickness as the 2.0.
brucet

Richard/Dover/theKong/Frogman others.

I find this significant based on the recent damping conversations. I will have more information coming from Bruce when he has time to discuss. I feel this info will enlighten us. The only clue I have been given.

"horizontal resonance to be above 2-3Hz but at least 4 to 5Hz below the vertical resonance"



TWEAK

I have also come up with something that I believe is significant as far as sonics are concerned and requires only a one minute adjustment. This is based on only one listening session but is so easy to try I had to share it.

Loosen the end cap bolt (not the leaf spring bolt we have been discussing) just enough to lower the lead weights, so that they are positioned at the bottom half of the spindle; when looking at the arm from the gooseneck side. Once done tighten end cap again.

This increases the VTF significantly.

You will need to adjust by moving the lead farther out on the I Beam. A good thing.

Cheers