STP distance. Is it critical ?

Changing one of the three "dimensions" changes the other two for a given geometry. If the STP increases, so does the effective length, the cartridge offset angle shallows.

This only makes sense...

As P-to-S increases, effective length must increase (logically). Also, as P-to-S increases, overhang decreases and cartridge offset angle shallows.

Taken to the extreme (as P-to-S goes to infinity), the overhang goes to 0 (as P-to-S and effective length becomes equal) and offset angle goes to 0 as well. This is what a linear tracking arm attempts to mimic.

No thanks necessary for me pointing out the obvious. I'm here to help.

Raul,

The issue with the SME V is that the holes for cartridge mounting do not allow for any other cartridge position or adjustment of the cartridge in the headshell. This would be OK if all cartridges used the same "mounting hole to stylus distance." Bit there is no standard value for the position of the stylus relative to the mounting holes in the cartridge. Therefore, as the position of the stylus relative to the mounting holes changes, then so does the effective length of the arm. Since the effective length changes, so does the STP distance. Increase the effective length and the STP, and the cartridge offset angle must decrease.

So the geometry of the SME arm changes most every time there is a change of cartridge. In some cases, it seems that the cartridge offset angle will not be a good match the effective length / STP.

Even though we're talking about VERY MINUTE differences, I wonder if that might be one of the reasons that the SME V arm doesn't seem to perform as well for some users.

Bill

Dear Raul, If I understand the design of SME V then the designers assumed the exact position of the stylus in all
carts. Otherwise thy would make slots in the headshell.
The actual carts are some kind of 'movenig targets'in this
respect. So to get the right eff. lenght or those null points one must 'slide' the arm and consequently change the SPD. If I understand J. Carr correctly one should recalculate the geometry for the 'deviant carts'. BTW in some other models SME changed the headshell.

Regards,

There is a range of tracking errors that sound similar if not identical. (I would admit that with certain vinyl setups the differences may be more noticeable.) To provide some perspective: Given the gamut of alignments, including Lofgren A (Baerwald), Lofgren B, and Stevenson plus the myriad of "custom" geometries and alignments, each considered optimal to portions of the vinyl audiophile community, there is more than one "optimal" alignment geometry.

I use a SME tone arm and the differences in tracking error from one cartridge to the next are so slight that I do not worry about it. Some cartridges result in less distortion across the mid-section of the groove while others have less distortion at the beginning and end of the groove. I've learned to accept the range of alignments and would be hard pressed to detect the differences with many if not most records anyway.

So when we start to nit pick over the merits or disadvantages of specific modulated groove radii, null point radii, and nominal effective lengths, I believe we're teetering on the edge of being bumptious if not dilusional.

I would agree that certain combinations of cartridge and tone arm may not play nicely with certain alignments and that there are some cartridges with atypical mounting hole parameters that will not work well with fixed headshell offset angles, but within the range of typical cartridge and tone arm geometries there is a range of alignments that play and sound just fine.

Or not. :-)

TomTom

Dear Tketcham, I quoted Carr in my post from memory but the
thread is:'Allignment tool for SME V + Shelter'. To prevent any suggestion of 'belittling' the SME V I need to
add that all the owners , Carr included, are very fond about their tonearm. However even Carr admited that because of those holes in the headshell one needs to adjust the geometry to accommodate 'some carts'.As he put
it:'Simply recalculate and readjust the overhang,likewise
for the offset angle (the ...difference between screwhole diameter and srew diameter should be enough to accomodate the majority of carts)'. Well simplicity as well as complexity are persons-relative so I bought Triplanar because of my math.
While this thread is already complex I don't believe that
adding 'the range of tracking errors that sound similar'
will help to simplifid the issues.

Regards,