Nandric: In recent years I have tried to stay with 9.52mm (not 9.25) for the distance between a cartridge's stylus and mounting holes, first because maintaining a specific distance makes it easier to swap cartridges, second because I am unaware of any other number that has ever been suggested as a possible cross-manufacturer standard. However, I have never heard any other cartridge manufacturer say that they consider 9.52mm to be a standard that they try to keep.
Looking at the various models in a single manufacturer's lineup, it appears that there can be variations in this distance. This has to do with whether the manufacturer even considers 9.52mm to be a standard, and it also has to do with the mechanical design policies of the manufacturer. Some manufacturers have a single basic mechanical design that they differentiate for different models with a variety of cantilever materials, core materials or outer bodies. For such manufacturers it should be easy to keep a standard mounting distance. Other manufacturers may have evolved through a lot of different mechanical design structures over the years (like us), or may have different mechanical design structures coexisting at the same time in their model lineup (like Dynavector). For these manufacturers, to keep to a single mounting distance is much more work, not the least because it may at times get in the way of other priorities for an individual design.
Therefore I wouldn't necessarily consider 9.52mm as a standard. A standard isn't a standard if the majority of people that it applies to ignore it, or obey it on a case-by-case basis. It would be useful if there was a database that showed the stylus-to-mounting hole distances for various manufacturers and models, but I am not aware of any such database. I don't even know if all manufacturers make such data known.
I agree that the combination of arc-type protractors and tonearms with fixed-hole headshells can be a headache. In reality, if the user understands tonearm geometry, it is not a problem to achieve Baerwald alignment even if the cartridge doesn't adhere to 9.52mm (and the effective length therefore changes). Simply recalculate and readjust the overhang (via the SME's sliding base), likewise for the offset angle (the difference in diameter between screwhole diameter and screw diameter should be enough to accommodate the majority of cases). The tonearm geometry will now be a little different from what SME designed for, and you most likely will need to switch to another alignment gauge (not an arc-type). Not as convenient, but the results should sound fine, which is the most important thing.
FWIW, different cartridge manufacturers appear to use mounting screw diameters of either 2.5mm or 2.6mm. Close to a standard, but not quite achieving it. Deja vu (^o^).
cheers,
Looking at the various models in a single manufacturer's lineup, it appears that there can be variations in this distance. This has to do with whether the manufacturer even considers 9.52mm to be a standard, and it also has to do with the mechanical design policies of the manufacturer. Some manufacturers have a single basic mechanical design that they differentiate for different models with a variety of cantilever materials, core materials or outer bodies. For such manufacturers it should be easy to keep a standard mounting distance. Other manufacturers may have evolved through a lot of different mechanical design structures over the years (like us), or may have different mechanical design structures coexisting at the same time in their model lineup (like Dynavector). For these manufacturers, to keep to a single mounting distance is much more work, not the least because it may at times get in the way of other priorities for an individual design.
Therefore I wouldn't necessarily consider 9.52mm as a standard. A standard isn't a standard if the majority of people that it applies to ignore it, or obey it on a case-by-case basis. It would be useful if there was a database that showed the stylus-to-mounting hole distances for various manufacturers and models, but I am not aware of any such database. I don't even know if all manufacturers make such data known.
I agree that the combination of arc-type protractors and tonearms with fixed-hole headshells can be a headache. In reality, if the user understands tonearm geometry, it is not a problem to achieve Baerwald alignment even if the cartridge doesn't adhere to 9.52mm (and the effective length therefore changes). Simply recalculate and readjust the overhang (via the SME's sliding base), likewise for the offset angle (the difference in diameter between screwhole diameter and screw diameter should be enough to accommodate the majority of cases). The tonearm geometry will now be a little different from what SME designed for, and you most likely will need to switch to another alignment gauge (not an arc-type). Not as convenient, but the results should sound fine, which is the most important thing.
FWIW, different cartridge manufacturers appear to use mounting screw diameters of either 2.5mm or 2.6mm. Close to a standard, but not quite achieving it. Deja vu (^o^).
cheers,