Alignment tool for SME V + Shelter

Dan, the SME slide mount moves the entire tonearm (pivot and all) back and forth, pretty much toward or away from the spindle. Moving this carriage does not change the arm length, which on an SME is 233mm from pivot to the tip of the stylus (of a cartridge with standard stylus-to-mounting hole dimensions.)

Because of the fixed cartridge mounting holes, the arm length of an SME (and pretty much ONLY an SME) wiil increase/decrease by however much more or less the stylus-to-cartridge-mounting-hole dimension deviates from the standard. I.e., if the stylus is forward of the cartridge mounting holes say 2mm more than standard, the the effective length of the SME arm will be 235mm, not 233mm. It's not a disaster though, because you simply have to increase the overhang a tiny amount (according to a chart) and everything goes back into proper relationship.

Personally, I'd advise anyone using an SME IV or V to use cartridges with standard stylus-to-mounting hole dimensions. It makes life easier and still leaves a zillion cartridges to choose from ;-).

Setting up proper SME arm geometry involves two steps:
1,) checking/setting the stylus overhang (using the sliding carriage base), and
2.) adjusting the cartridge horizontally to align with the gridlines of a DB (or other conventional protractor) at the two null points (there's enough play in the mounting holes to allow this adjustment.) And that's it ;-)

Nsgarch, I hope you get the chance to try an arc-protractor and even better, a MintLp protractor. A good look and it is easy to see why there are much better tools available. Whatever works for you. :-)

Dear Nsgard,To use an semantic argument: you think that the expression 'youngsters' is 'correct' but the expression 'young people' is 'incorrect'. But you must wriggle yourself to explain that your beloved SME V is not
capable to accomodate 'deviant carts' because the headshell
of the SME has holes and,alas,not slots. According to J.Carr the 'norm' should be 9,25mm but the problem is that
many carts dont 'obey' this norm. So what are the slots for? To get the right eff.length by 'correcting',so to speak,the 'deviant carts'. So we are talking about the same
thing.
But of more importance was my question about the'right aid'to measure the spindle-pivot distance,the 'deviant' spindle diameter included.
Your answer is something I know since 30 years: included by
your TT package. This will not do for me.I think that we
need to ask Yip (Mint LP) to provide such an 'aid' for the individual TT's.

Regards,

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,

Nandric, Jonathan Carr (who manufactures the very fine Lyra cartridges) and I agree completely, even though I said it somewhat differently.

I said:

Because of the fixed cartridge mounting holes, the arm length of an SME (and pretty much ONLY an SME) will increase/decrease by however much more or less the stylus-to-cartridge-mounting-hole dimension deviates from the standard. I.e., if the stylus is forward of the cartridge mounting holes say 2mm more than standard, the the effective length of the SME arm will be 235mm, not 233mm. It's not a disaster though, because you simply have to increase the overhang a tiny amount (according to a chart) and everything goes back into proper relationship.
Personally, I'd advise anyone using an SME IV or V to use cartridges with standard stylus-to-mounting hole dimensions. It makes life easier and still leaves a zillion cartridges to choose from ;-).

He said:

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.

I also mentioned, as Jonathan did, that there is enough play in the SME mounting holes to provide for offset adjustment if necessary. Neither of us even suggested (much less stated) that an SME IV or V arm could not accomodate ANY cartridge, and I don't know how you came to that understanding. As for variations in spindle diameter - well they can't vary too much can they? ;-) It's only important that a template hole fit over the spindle without significant play - an easy thing to fix (if it occurs) with a couple turns of teflon tape. Drilling the armboard so the mounted tonearm winds up the proper distance from the spindle is far more important in my opinion, and not as easy as it seems at first.

My "beloved SME V" is the most rigid yet fluid cartridge mounting platform ever concieved. The fixed mounting holes are absolutely necessary for that achievement. In case you were unaware, SME makes a Model V with an adjustable headshell for those willing to trade the utmost performance for a bit more convenience.

Neil
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