Eminent Technology ET-2 Tonearm Owners

Do you know what PSI and Pump type your ET2 or ET2.5 was designed for ?

3.6 PSI - Original Takatsuki and ET-2 or 2.5

5.0- 7 PSI - WISA 300 air pump and ET-2 or 2.5 with high pressure manifolds

>10 PSI - users with shop compressors and ET-2 or 2.5 high pressure manifolds

Note, if the pressure readings are higher than those listed above, the manifold could be clogged, if the pressure readings are lower, this suggests that the pump may not be performing correctly.

(Taken from Bruce's website)

What other thread allows us to learn about fine wine from downunder and good English ?

Well I did enjoy that youtube video Dover. Not surprising that not much has changed with the actual record since 1958 when the film was made. I could say they don’t make records as good anymore....anyone disagree?
In 1958 - I was just a thought in my parents eyes till four years later. Does anyone listen to music in a shirt and tie anymore?

At the 4:40 mark is an excellent example imo of a speaker setup. Nearfield and eliminating room problems by taking the room out of the picture. I love those speakers spikes. We can learn lots from these films.

The fellow talking reminds me of my Grade 8 science teacher. The guy in the film does show a bit of a smile at the end however. My science teacher in middle school was a German fellow that never smiled.

Dover says.
"....on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."

I say.
"At 3x Fr the rise in response is almost zero."

In response to this question..

In the technical section you talk about phase shift beginning at 2 to 3 times the resonant frequency down to Fr.
Does this mean that there is a resonant peak at 3 x Fr or is this the point where the phase and response errors have reduced to low levels?

Bruce T says...
"This is the point where, above this frequency, the phase shift becomes minimal, as you approach the resonance frequency, the phase shift increases. I hope this helps, thank you very much."

brucet

Bruce uses the phrase "becomes minimal" I used the phrase "almost zero". Bruce and I are talking about the same phenomenon. Neither of us say it is zero because the curve is asymptotic to zero. It is this characteristic which causes designers in my industry to err on the side of caution and use 6xFr. A figure I have mentioned previously.

There is No resonant peak at 3x Fr. The amplitude and phase problems reduce the further we move above Fr. Exactly as shown on the transmissibility graph I posted, which is an accurate representation of what is happening with the arm at frequencies around Fr.

Ha_ha_he_man
Further to your request.

What I hear when making the counterweight arm solid with a suitably stiff structure and when using a low compliance cartridge is this...
The image is a little more focused. Individual elements within that image are a little more vivid.

I stress as Chris has quite corrctly pointed out, my arm is optomised for low compliance cartridges.
Further I now consider an oil trough to be manditory for this rig.

Not Utter Nonsense Dover, tell me about a resonant peak at 3 x Fr.

05-27-13: Richardkrebs
Dover says.
"....on an undamped standard ET with decoupled counterweight there is a resonant peak at 3 times the fundamental resonant frequency, and that this is reduced with fluid damping on a standard ET with decoupled counterweight."

I say.
"At 3x Fr the rise in response is almost zero."
In response to this question..
In the technical section you talk about phase shift beginning at 2 to 3 times the resonant frequency down to Fr.
Does this mean that there is a resonant peak at 3 x Fr or is this the point where the phase and response errors have reduced to low levels?
Bruce T says...
"This is the point where, above this frequency, the phase shift becomes minimal, as you approach the resonance frequency, the phase shift increases. I hope this helps, thank you very much."

Richardkrebs, you continue to conflate apples and oranges and misrepresent statements.

The technical section you refer to is for a standard ET, with a substantial rise in response below 20hz.

FLUID DYNAMIC DAMPING FOR THE ET-II
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

One can achieve a flat response by tuning the decoupled counterweight and keeping the horizontal mass and Q low as outlined in the ET manual and demonstrated in the Stereophile testing.

Your ET is not standard. You have doubled the horizontal mass of your arm by adding lead and you have removed the counterweight decoupling mechanism.

The effect of the 2 modifications you made to your arm is to increase the amplitude of the fundamental resonance by some 6-12db as shown by Bruce Thigpens testing.

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

The arm Bruce used for testing was deliberately set up with a high Q and very low compliance cartridge. The standard ET when used as outlined in the manual with a decoupled counterweight has a lower Q.

A low frequency sweep was performed twice on the tonearm, once without the damping trough and once with the damping trough. The cartridge used was of very low compliance and the tonearm was set up so that a high amplitude high Q resonance existed. The results of the test show a reduction in the amplitude of the resonance of about 8 dB (horizontal).

You continue to ignore Bruces stated view that increasing horizontal mass increases distortion

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,

Clearly the reduction of 8db is for a standard arm. In the case of your arm to which you have added lead, doubled the horizontal effective mass and removed the decoupling mechanism, all you are achieving is some reduction in the problems and distortions you have built into your arm.

You have misrepresented Bruce’s view on eccentric records,

05-20-13: Richardkrebs
BT uses at 30cu cartridge in his manual to calculate horizontal Fr. The arm weight he uses is 30gm plus 7gm for the cartridge. We have to assume that he is ok with this combination and that he is not worried about cantilever deflection on eccentric records.

This assumption again is just plain wrong. I quote from Bruce Thigpen’s ET website:

ET2 Manual page 47 :
“if you like to play severely eccentric records, ones with run out greater than 1/8th of an inch, then we suggest you use a low mass pivoted arm.”

It would be helpful to move this thread forward if you acknowledged the issues related to adding mass and move away from using examples, maths and quotes that are irrelevant and taken out of context.