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Multiple arms, multiple cartridges and geometry?

I have read the debates regarding the benefits of different tonearm geometries......Lofgren A and B, Baerwald, Stevenson etc....and I appreciate the benefits of choosing where, on the vinyl record, one wishes to have the least spread of distortion.
I also have read where certain arms seem to perform better with one or other of these geometries?

I have two turntables with three different arms on each one and I have a total of over twenty five different cartridges.
Four of those arms have removable headshells and twenty of my cartridges are mounted on their own headshells ready for installation into any of those four tonearms.
How then.......can I have different geometries for each arm if I don't wish to re-align a cartridge within its headshell depending on the arm in which its installed?
Surely......I must select a single geometry for all my arms so that the cartridges fixed to their headshells....are truly interchangeable?
128x128halcro
halcro's avatar
halcro OP
2,664 posts
 
Dover,
and the only changeover issues would be tracking weight and VTA.
That's what I thought and the principle I have been operating under?
However.....I fear that is not the case?
The effective lengths and overhangs being different for all my arms......means the arm geometry is not easily transferable?

Raul,
I agree that I need to accept the same geometrical alignment for all the arms I wish to use with detachable headshells......say Baerwald?
I can appreciate that I can adjust the P to S distance of each arm so that the 'Overhang' can be the same.......but I don't see how I can adjust the effective lengths between 222mm, 230mm or 295mm to be the same? :-(

Can you possible explain a bit more thoroughly?

Cheers
Henry
dougdeacon
3,338 posts
 
Nandric nailed it.

Get to work, and you might as well enter the S2IG (spindle-to-inner groove) dimension in a searchable database while you're at it.
nandric's avatar
nandric
4,086 posts
 
Dear Henry, Sorry, I overrated my Sliwowitz capacity. My
consideration was: the distance between the lead out
groove to the spindle differ by the most LP's. Depending from this distance Stivenson and Bearwald will give different inner 'O' points which means that one will be
more optimal than the other in (co) relation to the LP
you intend to play. You can estimate the distance or measure and then decide which tonearm (aka geometry) to use. Ie the geometry is primary about the records and only
'indirectly' about the tonearms.

Regards,
ecir38
155 posts
 
Halcro, thinking you may be able to work this backwards. ie allign MA505 to your chosen common allignment. Remove the headshell and put it on one of your other tonearms. Move P2S for that arm so that it follows the arc that the MA505 used then record the new P2S for future referance. Just a thought but not sure if this would work due to the differences of offset and overhang between the arms you use.
john_gordon
116 posts
 
Hi Halcro,
you said:
How then.......can I have different geometries for each arm if I don't wish to re-align a cartridge within its headshell depending on the arm in which its installed?
Surely......I must select a single geometry for all my arms so that the cartridges fixed to their headshells....are truly interchangeable?

I see you are still pursuing this quest. Previously I posted regarding a similar issue you asked about
...It looks to me that swapping headshells between arms would require them to be set up initially with oneheadshell/ cartridge combination which remained set once the first arm was done, and which was then used to set the remaining arms with adjustment achieved at the bases of the others, assuming they were different arms.

The alignment chosen would have to also be the same for each set up, irrespective of the arm design, but the arms could be different lengths. Then any cartridge/ headshellcombination could be set up to suit these alignments without moving the bases. This would depend on the headshells having slots, though the initial headshell could have holes as long as the arm used was designed to the chosen alignment.

So headshell swopping only works with arms of the same alignment. where one cartridge is used initially with one arm then that cartridge is used to set the mounting distance for the rest.

You could also set for Lofgren B, using the same headshell/cartridge by setting an arm closer to the spindle, thus increasing overhang by around half a millimetre (depending on effective length), as the cartridge offset remains the same using an adjustable base.

For other non LofgrenA arms you would have to know the offset angle and whether you could achieve a suitable alignment with a cartridge already mounted correctly for LofgrenA by adjusting the mounting distance only.

Have fun...

John
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