Dear all, to my knowledge the 9" and 12" denomination was introduced by SME with their original 3009 and 3012 tonearms (hence the names...3009 and 3012). Ever since then 9" and 12" is used to describe tonearms which do have an effective length around the 9" or 12" figure.
But they all do differ in their effective length - some are very close, hardly any is exactly the same as another.
Take a few 12" tonearms as example:
- SME 3012 - 307,34 mm
- MAX-282 - 282 mm
- FR-66s - 307 mm
- SAEC-506/30 - 295 mm
these are all named 12"-tonearms. 12" is 304.8 mm - so none of the above mentioned tonearms is really 12" in effective length.
Only the SME 3012 and the FR-66s are close to that measure. Same for the 9" SME 3009 which is VERY close with its 229 mm (the later 3009R has 231,80 mm.......).
Well - we can alter the effective length of any given pivot tonearm.
And we do.
We can do so easy and - in a certain and narrow range. We do this when we adjust/change overhang (and in the same procedure the related offset...) to achive for instance Baerwald or Loefgren based geometry. We had that topic already back in the thread about the "Oldskool tonearms".
Take again the Graham alignment tool.......... here you have a very good and clear example.
The base (= mounting distance) isn't moved at all. The change is done at the headshell by different overhang and offset.
The mounting distance is still fixed. You change overhang and offset to adjust to different zero-error points - not the mounting distance (at least..... you shouldn't....) - not the mounting distance P-S.
The mounting distance is the 1st and basic parameter of the calculation of any pivot bearing tonearm.
But they all do differ in their effective length - some are very close, hardly any is exactly the same as another.
Take a few 12" tonearms as example:
- SME 3012 - 307,34 mm
- MAX-282 - 282 mm
- FR-66s - 307 mm
- SAEC-506/30 - 295 mm
these are all named 12"-tonearms. 12" is 304.8 mm - so none of the above mentioned tonearms is really 12" in effective length.
Only the SME 3012 and the FR-66s are close to that measure. Same for the 9" SME 3009 which is VERY close with its 229 mm (the later 3009R has 231,80 mm.......).
Well - we can alter the effective length of any given pivot tonearm.
And we do.
We can do so easy and - in a certain and narrow range. We do this when we adjust/change overhang (and in the same procedure the related offset...) to achive for instance Baerwald or Loefgren based geometry. We had that topic already back in the thread about the "Oldskool tonearms".
Take again the Graham alignment tool.......... here you have a very good and clear example.
The base (= mounting distance) isn't moved at all. The change is done at the headshell by different overhang and offset.
The mounting distance is still fixed. You change overhang and offset to adjust to different zero-error points - not the mounting distance (at least..... you shouldn't....) - not the mounting distance P-S.
The mounting distance is the 1st and basic parameter of the calculation of any pivot bearing tonearm.
