Time to choose: Baerwald, Lofgren, Stevenson ?

I'm generally in the same camp as Lewm on this one: I align the cartridges based on the alignment the tonearm was designed for. Since most of my tonearms use removable head shells and were designed for a 52mm distance from the head shell connection to the stylus, this has the added benefit that the cartridge needs minimal if any realigning when put into another tonearm.

I may be missing something here.  I've had a long night on my CAD software and I'm a bit dimensionally challenged at the moment.

If you have two tonearms using universal headshells:

• Tonearm-A with effective length A and cartridge-A:  the tonearm is designed for Baerwaald and this cartridge/headshell is aligned for Baerwaald
  
• Tonearm-B with effective length B and cartridge-B:  the tonearm is designed for Stevenson and aligned as such.

If you swap the cartridge-B/headshell-B combo over to tonearm-A, you would absolutely need to perform a new alignment.  I guess I don't get the concept of minimal realignment.  It either needs a new setup (alignment) or it doesn't.

Even if both arms were aligned for the same geometry (e.g. Baerwaald), the different effective lengths would mandate a different offset angle..

The whole concept of effective length is a dangerous one, because, two tonearms specified (for example) to have an effective length of 250mm would have different pivot-spindle specifications if one was intended for Stevenson or Loefgren and the other for Baerwaald. 

I'm having problems visualizing any scenario where you could make any cross arm swapping work, but I'll ponder this one ;-)

Cheers,
Thom @ Galibier Design

Thom,

If the cartridge is aligned as designed by manufacturer, then the cartridge is straight in the headshell. Now move it another tonearm and align it according to that tonearm’s design: it will again be straight in the headshell. To the extent that the tonearms are designed to have different offset angles, those are manifest in the arm tube. So the only thing that could change then is how far in the headshell the cartridge is. But if both tonearms are designed to have the stylus 52mm from the tonearm connection, that doesn’t change either.

If you have difficulty visualizing this, then visualize moving an SPU from one tonearm to another. This is just replicating that with a normal cartridge & headshell.

sampsa55

If the cartridge is aligned as designed by manufacturer, then the cartridge is straight in the headshell.

Oh no, that's not at all necessarily the case. As others have pointed out, there's often a slight misalignment of the cantilever within the cartridge itself. Proper cartridge alignment aligns the cantilever to the record, and not the cartridge to the headshell. This is where mirrored alignment gauges - such as the WallyTracktor - really excel.

Thom, The issue of doing the twist (Chubby Checker, where are you now that we need you?) has most to do with using Baerwald or Lofgren with a tonearm designed for Stevenson. This issue therefore only or mostly comes up with vintage tonearms of the kind that you usually do not deal with. In my case, it’s a Dynavector DV505. To set up the DV505 for B or L, one has to twist the cartridge inward (such that the front end of the cartridge is skewed toward the spindle side of the headshell) quite a bit. And of course, when I use the term "cartridge", I am referring to the cantilever, which is what counts, regardless of the fact that some cartridges do not come to us with precisely aligned cantilevers. Ideally, the cantilever should move in an arc in the vertical plane; it’s possible that when the plane of that arc does not align with the vertical plane described by the tonearm bearing, vector forces on the cantilever would not even out. I actually suspect this is a real issue that may be confined to the DV505 and other DV tonearms, where there are two discrete bearing systems, one vertical and one horizontal at play. In these tonearms, the vertical bearing cannot move horizontally to compensate for such a misalignment of the arcs. Maybe that is why I heard distortion as a result.  Maybe it's a red herring for more conventional tonearms.

Oh no, that's not at all necessarily the case. As others have pointed out, there's often a slight misalignment of the cantilever within the cartridge itself. Proper cartridge alignment aligns the cantilever to the record, and not the cartridge to the headshell. 

As, lewm already indicated, that doesn't change the conclusion at all. If you align by the cantilever, then the cantilever (rather than the body) will be aligned straight in the headshell and will remain so in any arm if you use the alignment that the tonearm was designed for.