Ok, I know the OL Silver is a better match, in theory, with the 501, and may very well be in application.
On the other hand, I have a 501 in my Spacearm/Spacedeck combination. The results are excellent, and I have done a comparison to several other cartridges, costing both less and much more than the Shelter, that were supposed to be better matches in terms of compliance. I know a local dealer with 30+ years of experience who recommends the 501 with that combination and has quite a few happy buyers. Over the past six months he has A/B/C/D'd quite a number of carts on this arm and very few have been the equal of the 501.
One thing to remember about the Spacearm, at least I know this is true for the later carbon versions after a discussion with the designer - Tom Fletcher has engineered into the pivot two stabilizing rods (which you can see if you look under the pivot shell). He claims that these specifically placed bars render moot some of the concerns with regular unipivot arms. I am not technically educated enough to measure the difference made by these rods but I will say that the 501 does A LOT more than just "work" with the Spacearm. In fact, and based on experience, saying the 501 will merely "work" on a Spacearm is a total understatement and a disservice to both the arm and cartridge, though I know the person that said such had very good intentions. ;-)
On the other hand, I have a 501 in my Spacearm/Spacedeck combination. The results are excellent, and I have done a comparison to several other cartridges, costing both less and much more than the Shelter, that were supposed to be better matches in terms of compliance. I know a local dealer with 30+ years of experience who recommends the 501 with that combination and has quite a few happy buyers. Over the past six months he has A/B/C/D'd quite a number of carts on this arm and very few have been the equal of the 501.
One thing to remember about the Spacearm, at least I know this is true for the later carbon versions after a discussion with the designer - Tom Fletcher has engineered into the pivot two stabilizing rods (which you can see if you look under the pivot shell). He claims that these specifically placed bars render moot some of the concerns with regular unipivot arms. I am not technically educated enough to measure the difference made by these rods but I will say that the 501 does A LOT more than just "work" with the Spacearm. In fact, and based on experience, saying the 501 will merely "work" on a Spacearm is a total understatement and a disservice to both the arm and cartridge, though I know the person that said such had very good intentions. ;-)