SAEC 308N vs 308SX

Dear Nandric: 407/23 effective length 233mm and 12mm overhang according SAEC. The 308 has different values, I think ???.

regards and enjoy the music,
R.

Yes, Raul. You were correct earlier when you mentioned that the 407 (at 9 inches) is a bit shorter than the 308 (at about 9.5 inches).

Tonight I had a chance to go poking around on Vinyl Engine for more info on these two tonearms,
(1) It appears that Nicola may be correct; the "N" may stand for "NEW". On VE, there is a reprint of the brochure for 308NEW.
(2) The 308SX is shown with the ceramic headshell; the 308N does not have the ceramic headshell. So that was one difference. The SX version has larger heavier "ears" flanking the bearing housing, to increase lateral effective mass. The arm tube of the SX might or might not be different from the N.
(3) The P2S distance for the N and probably for the SX is given as 235mm. Only 5mm of stylus overhang is recommended, for an effective length of 240mm. With a headshell offset angle of only 12 degrees, this results in an inner null point of 39.2mm (!) and an outer null point of 60.6mm. The ad copy says no tracing distortion on innermost grooves. I can believe that, since at 39.2mm from the spindle, the stylus is at best reaching the run-out grooves if not only the outer edge of the label. At 60.6mm it would probably be within the innermost cut of the LP. So they compromised the tracking angle over the whole rest of the LP in order to minimize tracking angle error in the innermost grooves. In contrast, Stevenson results in null points at ~60mm and ~117mm. And Baerwald and Lofgren B both have their null points farther away from the spindle than Stevenson. So the SAEC geometry is strange, indeed. Why choose to set your tonearm up so that only one null point occurs where there is music? Dunno. For one thing, the small headshell offset angle would tend to reduce skating force.

Dear Lew, This is a quote about SEAC WE-308 SX from 'Tonearm Geometry and Setup' (Kessler&Pisha,Audio,January 1980): 'The SEAK WE-308 SX arm design is based upon research done by the Sansui Electric Co. The AES preprint 1390 (D-5) derived the optimum pivot position from a kinematic point of view,with
the mass of the arm ,the location of the center of gravity,
and the moment of inertia around the system's center of
gravity. Resonance was the engineering problem being solved. For this prticular arm ,it is not advised to optimize the geometry, or the resonance of the system will
change to such an extent that the arm will not track properly.'
So obviously this arm is not only unique qua price . BTW you should know that reaserch is very expesive and need to be earned back somehow. I assume that 308, 308N, 308 L and my 407/23 are not 'inflicted' with the Sansui research and
that te owners of those arms may 'mess' with different geometries? There is no other choice btw because SAEC is very confusing or not very clear about,say, the null points.

Regards,

Dear lewm, dear Nandric, dear Geoch, for those wondering about the odd geometry on many SAEC tonearms ( see 506 for instance ...). SAEC stated that these tonearms geometry was optimized for zero distortion in the inner grooves.
This wasn't smart.
However if used as a tonearm to play 7" singles, these SAEC's geometry shines in a all new light .......
Whatever motivation it was that prompted SAECs engineers to design some of it's tonearms with a very odd geometry, they can all be "re-adjusted" to Baerwald/Loefgren/Stevenson et al - if however at the expense of sometimes very odd off-set position in headshell/mount and altered breakdown torque with effects on skating force.
Cheers,
D.