STP distance. Is it critical ?

Dear Bill, J. Carr proposed 'éasy way' out for the SME V:
recalculate the geometry (thread reg. SME V?).
My (other) question. According to SAEC engeneers the balance in all 3 dimensions across the radius is of much
importance. Can you explain this claim?

Regards,

Dear Nandric: ++++ " But we all
are trying to get the stylus on those null points. But if
we use,say,SME V with holes and ...." +++++

I can't understand what you exactly men with the V.

SME V was designed with Baerwald geometry, its null point are right " there " .

If your tonearm is mounted with the precise STP distance then you have not any single problem to achieve the SME null point.

Please let me know what I'm missing here.

regards and enjoy the music,
Raul.

Dear Nandric,

I agree with Jonathan (who am I to disagree with such an expert!?).

The way I read the SAEC engineer statement emphasizes what is being discussed in the thread. 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. Each geometry has a different ratio, but the same principles apply.

If one of the dimensions change without changing the other two, then the geometry is different.

Take a glance at this table to see how the dimensions are interrelated. This table is for a single geometry / location of null points. Other geometries will have different ratios.

http://www.audioasylum.com/audio/vinyl/messages/77287.html

BTW, the dimensions illustrated in this table vary a little from the ones provided my Micro Seiki for the MA-505 standard length arm (237mm, 222mm, 21 degrees 50 minutes) which uses a different geometry.

HTH,

Bill

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