Eminent Technology ET-2 Tonearm Owners

Dover.

Up till recently you have been telling us all repeatedly that the counterweight decoupling spring is active at eccentric record frequencies and that at these frequencies my arm is up to 300% heavier than a standard ET2. We now all know that you are wrong and that the spring is in fact rigid at this low frequency making the effective mass seen by the cart in standard ET2's in the same ball park as my arm with a fixed counterweight.
The math which proves this effect, below FR, shows that above FR the decoupling spring is active and it dramatically reduces the arms effective mass. This is a brilliant solution if you are using a high compliance cartridge. But this same math shows that if the FR is around 7Hz or above, we get bass attenuation. Low compliance carts will exhibit a FR in this danger zone of 7Hz and above. If we fix the counterweight, to push FR below the danger zone, we unfortunately get a big, high Q peak at FR. Exactly what the leaf spring fixes for us. So there is a conundrum here. Live without the last bit of bass extension or fix the counterweight and experience bloated bass performance, not due to excessive bass but due to the FM phase problems propagating up from FR into the audible spectrum. On the bloated bass topic we agree.

But there are solutions to this. Run the arm at pressures below design and dress the lead out wires to resist lateral movement. Not a very elegant solution but it kinda works. Or far more effective, ran at design pressures and use an oil trough. See BT's test data on this where he uses his arm "set up so that a high amplitude Q existed" (a fixed counterweight exhibits a high Q) and then adds the oil trough. The resultant response graph he publishes in the oil trough manual, shows a critically damped system with zero resonant peak and importantly he mentions "the ET2 with a damping trough will exhibit almost perfect low frequency phase response"
No more bloated bass and with full LF extension. Lovely.

Thanks for the comments. I had forgotten that the ET1's counterweight arrangement was not decoupled. While I can't speak to why the reviewers that I mentioned considered the weightier bass of the 1 to be "superior", I do agree with Dover that, based on my experimentation, decoupling the counter weight wand does result in bass that is more tuneful and correctly speedy than with more direct coupling.

01-28-14: Richardkrebs
Dover.
Up till recently you have been telling us all repeatedly that the counterweight decoupling spring is active at eccentric record frequencies and that at these frequencies my arm is up to 300% heavier than a standard ET2. We now all know that you are wrong

Yet again you have misquoted me.
I said that your arm is 300% heavier than standard based on the information you provided. You claimed that you had added 30g of lead mass to the 25g spindle and that you had converted the decoupled counterweight (30g+) to a fixed counterweight.

01-28-14: Richardkrebs
The math which proves this effect, below FR, shows that above FR the decoupling spring is active and it dramatically reduces the arms effective mass.

So now you have contradicted yourself and agree that the decoupling reduces the effective mass. This means that based on your assertion that you added 30g of lead to your arm and removed the decoupling then you have indeed increased the effective mass by 300% or thereabouts.

01-28-14: Richardkrebs
If we fix the counterweight, to push FR below the danger zone, we unfortunately get a big, high Q peak at FR. Exactly what the leaf spring fixes for us. So there is a conundrum here. Live without the last bit of bass extension or fix the counterweight and experience bloated bass performance, not due to excessive bass but due to the FM phase problems propagating up from FR into the audible spectrum. On the bloated bass topic we agree.

You now concede that fixing the counterweight will generate bloated bass as documented on Bruce Thigpens website. Since you also have acknowledged that fixing the counterweight increases the effective mass above FR, then fixing the counterweight will have deleterious effects on bass, midrange, treble - where the music is.

01-28-14: Richardkrebs
But there are solutions to this. Run the arm at pressures below design and dress the lead out wires to resist lateral movement. Not a very elegant solution but it kinda works.

This is a terrible solution. You are proposing to run the arm at air pressures below the air bearings design parameters and/or increase resistance to lateral motion by putting tension on the lead out wires.
Others on this thread including Frogman, Slaw, Ct0517 have reported significant improvements in sound quality by increasing the operating pressure and reducing any drag added by the lead out wires. You are proposing the opposite. Most systems with a reasonable level of resolution are capable of demonstrating the effects of increasing horizontal effective mass.

01-28-14: Richardkrebs
Or far more effective, ran at design pressures and use an oil trough. See BT's test data on this where he uses his arm "set up so that a high amplitude Q existed" (a fixed counterweight exhibits a high Q) and then adds the oil trough. The resultant response graph he publishes in the oil trough manual, shows a critically damped system with zero resonant peak and importantly he mentions "the ET2 with a damping trough will exhibit almost perfect low frequency phase response"
No more bloated bass and with full LF extension. Lovely.

You have misunderstood BT's testing protocols and conclusions.
BT says "the ET2 with a damping trough will exhibit almost perfect low frequency phase response". He is referring to a standard ET2 that has not had lead mass added and has not had the decoupling removed. It should be noted that the damping paddle is designed to provide dampening in the vertical plane, but less so in the horizontal plane. This is why it is wide and thin. The fluid damping is designed to address record groove irregularities which cause scrubbing and oscillation as the stylus tracks. This is documented on BT's website and is also documented in the Shure white papers on trackability.

In summary the changes you have made to your ET2 including adding mass and removing the decoupling are contrary to the fundamental design principles and advantages of the ET2 and should be discarded.

Dover.
"yet again you miss quote me"
I think not. See your post 03-13-13. Where you go to great lengths to show, incorrectly, that when tracing eccentric records, my arm is 300% heavier than a standard ET2.
The leaf spring is inactive at eccentric record frequencies. ALL ET2's and my arm are of similar effective mass as seen by the cartridge under these conditions.

I am on record stating the clear superiority of the oil trough over my previous low pressure damping method.

Dover
"provide damping in the vertical plane and less in the horizontal"
Wrong. A quote from the oil trough manual "The design of the paddle and its position mean that it will be much more effective for damping horizontal resonances than vertical"
This is a simple paddle shape and lever effect. The arm has no leverage over the oil paddle in the horizontal plane but has the full length of the arm wand in the vertical. The target is horizontal damping. This is why BT publishes the before and after responses of horizontal resonance. Where the nasty high Q resonant peak is effectively eliminated.

Frogman.

If you are using a low compliance cartridge, have you tried a properly stiff fixed counterweight with an oil trough fitted? Disabling the leaf spring(s), say by wedging match sticks in the gaps, gives a hint at the effect, but the counterweight I beam is too flexible (it was never designed to be stiff) to show the true differences.

Hi Greg

I looked at it again and see that the pump has just come loose from the springs. The intermediate shelf looks solid and the springs are still attached there. What I can see of the spring mounts on the pump look ok too.

I suspect it was banged around or dropped and that pulled the pump loose from the springs... and then it was banged around a lot afterwards to nearly pulverize the plastic housing.

that is a little better news. the shipper must have had the thing close to upside down at one point for it to come off one of the springs? That Timeter pump hanging in its enclosure, reminds me of the pics and videos I have seen in the past of those eccentric vinyl guys (women audiophiles would never do this ?) who hang their entire turntables from the ceiling beams with long thick cables for isolation and to avoid vibrations. Thats the idea here as well and the first time of I have ever seen a motor mounted this way.

Look forward to hearing your progress with it. Cheers