Eminent Technology ET-2 Tonearm Owners

Richardkrebs

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

Shown here is a link to the Math on driven harmonic oscillators, a mathematical representation of an arm/ cartridge assembly.

The arm/cartridge/record interface has 2 fulcrum points -
The stylus point around which the cantilever pivots.
The cantilever suspension point, about which the cantilever also pivots, but which is partially constrained by the rubber suspension damping.

The forces involved are double ended - you have the groove applying a force to one end of the cantilever via the stylus. The other end of the cantilever has an restorative forces being applied from the arm motion.
The 2 forces are not in sync because there is a suspension joint between the cantilever and the arm.
Think of 2 people holding a pipe and each one trying to move it sideways out of sync with the other. That's what the cantilever experiences.

The model you are working with is irrelevant. It is too simplistic. If you had studied mechanical engineering you would understand this better.

if we take say 5 hz as the resonant frequency, we see that it will not be until we reach say 30hz before we have complete conversion into an output voltage. I dont think that this is desirable.

Making the arm lighter still will extend this frequency upwards.

This is the classic mistake made by an untrained ear. Let's add mass, lower the resonant frequency and we get more bottom end.
Dont worry about the increase in distortion through the upperbass, midrange and top end from the cantilever being forced to deflect further.

Richard, you have not answered the question posed in my earlier post..

Bruce Thigpen has confirmed that Richardkrebs assertion that ‘the cartridge is able to move the arms weight, start it and stop it, without cantilever deflection’ is wrong.

The following are quoted from the correspondence with Bruce Thigpen:
the cartridge will "see" .55Hz mounted in any tonearm, more so in one with higher horizontal inertia

I don't think Kuzma means the stylus does not deflect at all at .55Hz, that would defy physics

The question I am still waiting for a response is:

Does the cantilever deflect below resonance ?

Just give me a straight answer - Yes or No

Hi Thekong

During the testing phase, my ET2.5 will be set up with a ClearAudio Sigma.
When the final comparison comes, I will be using the Ortofon A90 between the Rockport and the ET.

Look forward to your observations.
Based on their specs for compliance and weight with similar spec carts I own, I have had really good experiences with the double leaf spring I beam.

It would be very easy to compare your custom counterweight later on to the decoupled counterweight.

If you contact Bruce he can send you a couple empty I beams with 5 loose leaf springs that you can glue in yourself to make a double and triple I beam. The beams cost about 10 or 15 dollars.

Three are shown in this pic.

single, double and triple

The double in the middle does not have the extra weight on it so looks thinner. The one I am holding is a triple and it makes the I Beam very rigid.

Will use it with the heavy, low compliance XV1.

I posted this earlier somewhere from Bruce on his opinion of the different I Beams.

With respect to the i-beams, this is correct: a stiffer (lower compliance) I Beam works better with a lower compliance cartridge.

Hope this helps - brucet

Cheers Chris

Dover
Again you enter into needless personal attacks

Does the cantilever deflect due to the higher lateral forces imposed upon it?
I see no movement with my cart tracking eccentric records and the math predicts none. However in absolute terms no one could say that there is zero deflection. A more appropriate question would be. Is the additional horizontal mass dangerous to the health of the cartridge, which has been your accretion all along. It would seem that this is not so. There appears to be no issue. If there was it would be all over the web that arm XYZ is a mass murderer.

The second important question should be. Does increasing the effective mass of the ET2 make its performance better or worse. For those of us with untrained ears the answer is yes.
We would need to include BT in at least a semi trained ear camp, as he advocates stiffening the counterweight beam on the arm he designed when using low compliance carts. This is counter to what you advocate when you loosen further the leaf spring.

I like your analogy of a pipe being moved independently at each end.
This of course presupposes that the cartridge body is moving relative to the groove. If it is not, which is what we want, the cantilever has one fixed pivot point at the suspension. The stylus end describes an arc as it traces the groove.

Richardkrebs,

There was no personal attack. I simply addressed the anomalies and reasons for the errors in your post dated 03-14-13.

I will review your latest post tomorrow.

Richardkrebs

With regard to cantilever deflection on eccentric records, it is clear you are confused. Let me explain:

Your original statements on this matter were and I quote
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.

03-13-13: Richardkrebs
What I have constantly said is that this force will not be enough to deflect the cantilever while tracing an eccentric record, provided the resonant frequency of the arm / cartridge system is above 0.55 hz for a 33 rpm and 0.75 hz for a 45 rpm record.[/quote]

Now however your position is, and I quote from your post of 03-16-13:

I see no movement with my cart tracking eccentric records and the math predicts none. However in absolute terms no one could say that there is zero deflection.

Richard, you have made two conflicting statements in two consecutive sentences in your latest post of 03-16-13.

Your first sentence states the maths predicts no cantilever deflection.
Your next sentence contradicts that sentence and all your previous assertions for the past week or two and states that no one could say there is no deflection.

Should readers of this thread take it that you now agree that Bruce Thigpen and I are correct and there is cantilever deflection below the resonant frequency. You were incorrect when you stated "Below this resonant frequency the cartridge is able to move the arms weight, start it and stop it, without cantilever deflection".