05-17-13: Richardkrebs
Dover
I do wish you would stop repeating your fundamental error ad nauseum.
I am not aware of any errors on my part. Please read my last post. It outlines the errors you have made.
Let’s address the fundamentals:
The ET2 has a unique patented decoupled counterweight.
The decoupled counterweight is damped at its natural resonant frequency of 2-5hz. This decreases the rise in frequency response at the fundamental resonance. ( page 9 of the ET2 manual ).
So with your cartridge a standard arm would have a fundamental resonance at 8hz, and the decoupled counterweight reduces the amplitude or size of this resonance.
Removing the decoupling as you have done will see an increase in the resonance of 6-12db – as shown in Bruce’s testing, documented on his website.
Now you state you have added some 62+g of mass to your ET2 and removed the decoupling.
So there are 2 points here:
1. Removing the decoupling increases the fundamental resonance by 6-12db.
2. Increasing the mass has reduced your FR to 5hz.
One can see that by adding mass you have placed the fundamental resonance in the same zone as the natural resonance of the decoupled counterweight. This would be a disaster as the 2 resonances will likely sum together to create a large one.
You can deduce from this that removing the decoupling not only takes out a fundamental design feature of this arm that provides a flat response in the bass, it actually compounds the problem of the FR peak and makes it doubly worse.
Now let’s assume that your system has no response below 30hz, just for arguments sake, not that I’m suggesting it does.
The reality is that phase shifts at fundamental resonance ( bass in my language ) will affect the rest of the frequency spectrum. In other words it affects the mid and highs.
ET website
If a tonearm/cartridge system has a substantial rise in response below 20 Hz as most do, the phase response at the low end will be shifted and phase shift will occur beginning at 2 to 3 times the resonant frequency down to Fr. The time in which low frequency signals come from the tonearm will be shifted slightly with respect to mid-range frequencies within the audible range and substantially shifted up to several periods at resonance.
One can clearly hear these distortions when adding mass to the ET2 and removing the decoupling spring.
05-17-13: Richardkrebs
Bruce measurements show that this rise in response is reduced by 8db with the addition of an oil trough. This in test conditions which used a deliberately high Q and a low compliance cart. The amplitude of resonance decreases the further you move away from Fr. BT suggests that resonance effects frequencies up to 3xFr.
This testing is irrelevant in your case because of what you have done to your ET2. The testing was conducted with a standard ET2 with a decoupled counterweight and fluid damping added - the total horizontal effective mass was approx. 54g.
You have altered your ET2 by removing the decoupling of the counterweight, which increases FR by 6-12db and increases the horizontal effective mass by 32g. You have also added 30g of lead to your tonearm. Your tonearm weighs approx. 114g compared to the 52g tested by Thigpen.
Thigpens test results cannot be applied to support your argument that your arm does not have a rise in response in the bottom end because you have doubled the weight of your arm and removed the decoupling mechanism from the counterweight.
What you have not addressed, other than the discussion on the impact of FR, is the tracking distortion that is generated by increasing the mass of the arm, in your case more than doubling it.
I quote from Bruce Thigpen:
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,
You have doubled the weight as seen by the cantilever.
A conventional pivoted arm with an effective mass of 14g with a cartridge of 9g will have a total effective mass of 23g.
The standard ET2 has a horizontal effective mass of 34g or 52g with the damping mechanism.
With your addition of lead and removal of the decoupling, and added fluid damping, your altered ET2 has an effective mass of approximately 114g - 4 times the effective mass of a conventional pivoted arm.
Readers should try to imagine waking around with the weight of three adults sitting on their shoulders, and pretending the weight is of no consequence.
This is what the cantilever has to endure with the Krebs alterations to the ET2.
