Hi everyone,
A few additional thoughts on the issue of an "ideal" fres of the arm/cart combo. I second Rauls observation, that even "non-textbook" combinations can give stunning results. It is in the often found case that the table/arm/cart is exited by footfall or other causes, like record excentricity or, quite common, heavy, mass loaded decks, sitting on top of tall racks(doing the Eiffel Tower dance), that the choice of a f.res that is least perceptible to being excited is beneficial.
This doesn't always mean the f.res has to be farthest away from the f.exite. If your f.res is a (2nd,3rd)multiple of f.excite, the alteration of f.res, be it lowering or raising(sometimes by a small amount only), will result in a sound improvement, more so with undamped arms than with damped arms.
This is why I aim at 11Hz. Most suspended tables have a f.suspension no higher than 4,5Hz, so you should be safe at anything higher than f.res=9Hz. Your suspension resonates at a lower frequency? You're safe going lower than 9Hz.
If you have a mass loaded deck, then footfall or the deck on a tall rack forming the bob of a reversed pendulum are your main concerns(the deck moving sideways, not up and down).
On the other hand, going higher than f.res=14hz will have an effect on the low frequency response of your system, in the worst case causing your amp to waist power on the speakers, prematurely saturate the output trannies on your tube amp,, or (a friend experienced it on some BIIIG Infinity Speakers, -3db at 15Hz) severe feedback.
If your table is mounted on/like a rock, or it's suspension is well designed, then you get to enjoy listening to any combination your collection allows you to put together and the actual sonic qualities of the arm or cart will dictate the outcome.
Sounds like Raul is one of those lucky guys!
All the best,
Frank