Eminent Technology ET-2 Tonearm Owners

Richardkrebs -

You have now conceded after 4-5 weeks of obfuscation that there is cantilever deflection on eccentric records below the resonant frequency.

It follows that adding mass increases deflection as I asserted back in February. On 02-16-13:

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.

Your latest comparison of the deflection of a sprung cantilever with the elasticity of a silk thread is at odds with the application of scientific principles.

Do we need to spend another 5 weeks going through the difference between the modulus of elasticity of a woven silk thread and the bending motion of a cantilevered suspension.

Hasn't this discussion run its course.

This is the third time that I'm aware of over the past weeks that you have requested a discussion be terminated. It is not obligatory for anyone to participate. Whilst you are keen to champion your Technics modifications and your own homebrew tonearm, this is not your personal thread.

No confusion at all. In Engineering, the term absolute is.....absolute.

This not correct. The discussion we are having is on the cantilever flex generated by an eccentric record. This is not absolute as there are variables involved, to wit - the mass and inertia of the arm, the compliance of the cartridge and the level of eccentricity in the record.

The laws of physics are absolute. Correctly applied they enable us to develop mathematical models for scenarios that are not absolute.

Some impressions –

First

Some text from Richards very interesting post of 03/14/13

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1325551242&openflup&527&4#527

For input frequencies that are 300% of the resonant frequency we get transmissibility of around 15%, unless the structure is highly damped and we all agree, I think, that lots of damping doesn't sound good.

So at 3x the resonant frequency we are loosing around 15% of the groove modulation, as the arm is still at this point moving back and forth sideways slightly.

This is not a problem provided this 3 x resonant frequency is not a valid audio signal. Actually you would need to extend the graph out to around 6x resonant frequency before the transmissibility was approaching 0. Until we reach that point, part of the low frequency goove modulation goes into moving the cartridge and arm sideways and not into generating an output voltage.

Now Page 9 of the ET2 manual.

Adjustable Effective Mass

The effective mass of the tonearm is adjustable, both vertically and horizontally. The arm has low-medium mass vertically and medium to high mass horizontally.

Four counterweights allow the vertical / horizontal mass to be changed. For example; if the user decreases the amount of counterweights used, and moved the this position back (higher scale number) the horizontal inertia of the tonearm would go down and the vertical inertia would go up.

Decoupled Counterweights.

The effective mass of the arm horizontally is equal to the sum of its component parts. (It does not pivot) it needs to be as light as possible for low mass, however, making the arm too light sacrifices rigidity. By decoupling the counterweight system horizontally, but not vertically, the mass of the counterweight is not seen by the cartridge above a certain frequency and is lowered. This allows the use of heavier (more rigid) components in tonearm design without increasing effective mass.
The decoupling mechanism is damped at its natural frequency (2hz – 5hz). THIS DECREASES THE RISE IN FREQUENCY RESPONSE AT RESONANCE IMPROVING LOW FREQUENCY PERFORMANCE

Well it looks like Bruce studies this and note the text in upper case.

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MY IMPRESSIONS

ET 2.5 at 19 PSI. Use of a Time Aridyne Medical Pump which produces very little resonance at the source. (I don't dare say "never" on this thread :^) ....just joking....not

http://www.alliedhpi.com/images/zs168-263-002.pdf

It dumps moisture at the pump down a tube just like a cars AC unit. Have never seen a drop in the second regulator in my room – except for that incident where the pump outlet clogged (minerals in moisture) and sent moisture down the line. My room water trap bulb was half full before I noticed it !

Test Cartridge
Benz Micro MC3 Soundsmith Ruby Retip.
15 x 10 – 6cm/dyne (1.6 - 2.2 vtf) (weight 7.2 gms)
Used at 1.8 gms wide open at 47 k and loaded at 100.

My wiring is unshielded

http://cgim.audiogon.com/i/vs/i/f/1332259084.jpg

With the preamp inputs about two feet away from the ET2.5.
I have been listening to this cartridge for a few months now with a double leaf spring. Very enjoyable.

I inserted the triple leaf spring which effectively for any anyone that has tried this, turns the counterweight into a rigid one – imo. No movement at all. Defeats the decoupling.

Bass performance changed with the triple leaf spring in my room with the 801 monitors. Lets understand this is relatively speaking as the 801 have prodigious bass. But the effect of the leaf spring versus no leaf spring was noticeable in the ears with the sound compression in the room and this (15 x 10 (– 6)cm/dyne) cartridge. Bass performance was not as good with the triple leaf spring with this specific cartridge in MY room.

So I believe what I heard supports what is in the ET2 manual.

Maybe I will have different results with the even lower compliance XV1 soon ? It may sound better with the triple leaf spring. This will have to wait as I have amps arriving this week. Its easy to swap out Leaf springs. I am not going to hurry with the XV1 - for those aware of its history with me.

Guys - I have made a promise to myself not to email or contact Bruce anymore with questions until first reading the manual. It really is like having his knowledge in your back pocket.

Hi Thekong – do not know what speakers you are using but the above impressions, further support the reason I recommended the double leaf spring with your test cartridges based solely on their specs.

Cheers

Chris,
Thanks.

The results concur with both my own testing and the correct application of the laws of physics and sound engineering practice when setting up the ET2. The use of decoupling is an essential element to optimize the performance. To remove the decoupling and add mass is an ill conceived notion not supported by the laws of physics and cannot be recommended.

The removal of the decoupling mechanism and adding mass will result in an unnatural hump in the low bass as explained in the ET2 manual.

Chris.

I also thank you for your insightful testing of the ET2.5.
It confirms that adding too much mass, by way of locking the counterweight is not a good idea, if it takes the arm out of the appropriate resonant frequency range. I did say earlier that in my testing of the ET2, I added too much weight and had to backtrack. The key point being where does the arm in standard form sit relative to the optimum.

Adding additional weight to an ET2.5 would be inadvisable since it is already in the Goldilocks zone I mentioned. Namely its horizontal resonant frequency is in the range of 2-3hz, when using a decoupled counterweight and a low to med compliance cart.
Now bringing the ET2 down to this optimal range, that would be interesting. Are you able to fit 3 leaf springs to an ET2 carrying a low to med compliance cartridge?
Another question please. How stiff is the beam with the 3 leaf springs? As I mentioned earlier, the arm is very sensitive to any resonance at this point. I would urge caution if the resultant assembly rings in the audio band.

Richardkrebs

Readers of this thread will now see that you are contradicting yourself.

Adding additional weight to an ET2.5 would be inadvisable since it is already in the Goldilocks zone I mentioned. Namely its horizontal resonant frequency is in the range of 2-3hz, when using a decoupled counterweight and a low to med compliance cart.

Richardkrebs - this comment is unbelievable. This completely contradicts your earlier posts.

You encouraged Thekong to add horizontal mass to his ET2.5 and I quote;

03-12-13: Richardkrebs
Thekong
I don't know how long patents last, but would suggest the reason that Lloyd does not decouple the counterweight is simple.

It sounds better.

03-12-13: Richardkrebs
Thekong

We look forward to reading your comments.

03-13-13: Richardkrebs
Thekong.

Thanks for posting the photo of the counterweight arm. One suggestion is that you need to be very carefull with the stiffness of this. Any shake rattle and roll here is bad since it is no longer free to pivot about the leaf spring. I experimneted with the rod carrying the weight and finished up with an aluminium rod with a M10 thread for adjustment. Smaller diameters were quite flexable.

I repeat, you have now opined that it is inadvisable to add mass to an ET2.5, whilst you have been encouraging Thekong to add mass to his ET2.5 by coupling his counterweight and furthermore, stiffening the counterweight assembly with an M10 bolt no less.

Your advice on adding mass and coupling the counterweight has been wrong.

Earlier I advised readers to be aware of the pitfalls and possible deleterious consequences. In a response you hysterically claimed that I was scaring people off from trying your suggested modifications and accused me of being a scaremonger.
Richardkrebs - readers of this thread are quite capable of evaluating the arguments put forward for and against. I have a higher respect for the intelligence of the readers of this thread.

Your refusal to acknowledge the recommendations outlined in the ET manual, your continual refusal to acknowledge the laws of physics, and now a complete reversal on the advice given Thekong on his ET2.5 suggest that readers should disregard your advice completely.