Eminent Technology ET-2 Tonearm Owners

08-21-13: Ct0517
08-19-13: Dover
Interesting comments on the Terminator linear tracking arm from Dgarretson on the MM thread who has fabricated a lightweight carriage from carbon finer instead of aluminium....
08-16-13
The wand has dual front and rear counterweights for continuously adjustable vertical effective mass.
Total horizontal mass of arm, cradle, and carbon fiber sled is 45gm, and can be increased by weighting the air sled.
08-18-13:
I've tried it with as little as 35gm horizontal mass and as much as 100gm-- approximating the range of horizontal effective mass from ET to Kuzma airline. So far less horizontal mass sounds better in all instances. This does not hold true for vertical mass.

Interesting comments from DG as they relate to the Terminator arm. I have only seen pictures of it.

imo - it is not valid comparing the ET2, 2.5 and Kuzma Airline in this manner

Dgarretson is not comparing the ET2 & Kuzma. His post is quite clear - it is a report on the effect of running the Terminator with different horizontal effective masses.
At no point in his post is he comparing the ET2 and Kuzma tonearms.

Dover

Point taken - for some reason these comments from DG

08-18-13:
I've tried it with as little as 35gm horizontal mass and as much as 100gm-- approximating the range of horizontal effective mass from ET to Kuzma airline. So far less horizontal mass sounds better in all instances. This does not hold true for vertical mass.

Represented results and reference points to me and assumptions got made. This triggered a need in me to summarize some of the discussions that have been held here on this thread between the two tonearms. This is an unfortunate habit (summarizing) from my work career and the comments were not related to DG’s comments.

imo - it is not valid comparing the ET2, 2.5 and Kuzma Airline in this manner

bad wording on my part.

I certainly hope DG took no offence. I blame the summer heat.

Thanks for letting me ramble on and get off with only a warning – this time.

Hello Ct0517 & Dover, of course no offense taken. The discussions about the significance of variations in horizontal mass have been of interest here and in several AA and DIY forum threads. I have yet to try a really low-compliance cartridge on Trans-Fi-- which may change my current opinion that "less is more" w/r to horizontal mass. I've experienced this with a large number-high compliance MM/MI cartridges and a small samples of medium-compliance MCs.

I'd have to dig for the URL, but I recall that either Mark Kelly or Poul Ladergaard calculated the lateral stylus force applied by a linear tonearm as compared to force attributable to overhang and off-set in a conventional pivot arm. If as modeled, the lateral forces of a pivot arm(to which we must also add the tonearm's effective mass) are significantly greater than that of a 100gm linear arm, then this may suggest that a linear arm(whether 35gm or 100gm) cannot be faulted for its large lateral mass. Perhaps this is what F. Kuzma meant when he said that 100gm is "no big deal." In any case, I was not suggesting the relative superiority of any of the three very different linear arms under consideration.

Dgarretson.

I look forward to your tests on stiffer carts.

Also re pivoted arms, I argued inelegantly a way back that the offset angle on a pivoted arm has a multiplying effect on the effective mass as seen by the cartridge. That is, the cartridge is not expending all its effort in trying to rotate are arm but a vector of this force due to the offset angle. Then of course we have to take into account the asymmetrical nature of anti skate. This could be what Mark or Poul are referring to?
With these parameters at least, chalk up a big advantage to a linear arm.

Richardkrebs
the cartridge is not expending all its effort in trying to rotate are arm but a vector of this force due to the offset angle.

Actually it is the tracking angle that propels the arm inwards, which is different from offset angle. The skating forces are proportional to the tracking angle and tracking force. With higher tracking forces the skating force reduces. It also reduces with longer arms due to the reduced tracking angle. If you are tracking from about 2.5g with a 12" arm the skating force becomes very small, and if the tonearm is designed with breakdown torque taken into account at this point it is possible to run a pivoted arm without anti skate. Stylus profile also impacts the skating force. Ladegaards theory ignores these causal factors and assumes no anti skate is applied, therefore it is a worst case scenario and improbable in reality..

Conversely on eccentric records the high horizontal mass of a linear tracking arm will create tracking distortion. Very few records are truly round, and increasing the mass with lead on a linear tracker will increase the inertia of the arm in the horizontal plane and increase distortion on eccentric records due to cantilever flex. Thigpens' recommendations are that with records with an eccentricity of 1/8" a low mass pivoted arm will be superior.

Dgarretson - your listening experience that lower mass is giving superior results with the Terminator mirrors most ( actually all except for one ) of the users of the ET2 on this thread that have attained optimum sound quality from the correct application and tuning of the low mass/decoupled counterweight design parameters that the ET2 is based upon.