I didn't realize that SME had changed the design of the 309. Are you sure about that? Of course, I don't really know, so you could be right.
I did hear something about inner groove distortion influencing SME's decision to use a different geometry for the 300 series than was used for the SME V and IV, but I thought the inner groove distortion compliant was directed at the SME V and SME IV. The SME V was introduced first, then came the SME IV, and finally the 300 series was introduced. Both the SME V and SME IV are based on Löfgren "A" geometry with inner groove radius at 60.325-mm and outer groove radius at 146.05-mm. All 300 series tonearm are also based on Löfgren "A" geometry but with inner groove radius of 58.0-mm and outer groove radius of 146.0-mm.
It appears to me that the effective length of 232.2-mm and corresponding mounting distance of 213.4-mm are simply mistakes on the SME website and also in the manual. Perhaps I'm wrong, but if you look at the SME 310 and SME 312, the same mistakes do not exist. Moreover, those numbers do not correlate with any of the other parameters listed above them for offset angle, linear offset and overhang. Do you know what linear offset would be compatible with an effective length of 232.2-mm and mounting distance of 213.4-mm? It is definitely not 91.54-mm because that would provide a totally absurd alignment. See the graph below.
Best regards,
John Elison
