Very interesting post.
I think there are several different issues to be addressed when talking about string action.
The first differentiation might be:
a. what is possible
b. what is desirable.
As to a.: let say as a player I want a guitar that allows for its own full dynamical range (which is different for different instruments anyway) without buzz, than the result will still depend on the top construction and the maximum possible excursion of the top, as well es the construction details of the neck. So for every guitar with a given set of strings there will be a minimum values of action that will do it. Every bit going below that will compromise the premise of no buzz with full dynamics.
And because the construction details of the top and the neck has a lot to do with playability, ton and intonation, there certainly is a reason why luthiers pursue different ideas in this field. But when I like a guitar for it's ton and playability and intonation, I have to live with the fact that there is a limit of lowering the action.
As to b.: not for every player low action (or high action for that matter) is similarly desirable. It depends on how the fine muscle movements of my hands work. I for my part have the experience that I operate smoother with small movements, and big movements against big resistance make me awkward. So for me lower action is a plus, which is not for everybody.
Now, for a given guitar there is also an optimum height of strings above the top, because the torque exerted on the top depends of that, which has a direct bearing on the sound and volume achievable . So lowering action can also compromise the optimal sound.
This also depends on the neck angle and can be controlled by it; so a luthier aiming at low action and bigger torque would have to aim at the neck angle accordingly.
So here are indeed many variables in play, and mostly they cannot really be standardized IMHO, so there will be differences that don't indicate a better or worse making but rather construction differences that might serve a purpose.
As to measuring: I use a ruler with 1/2 mm gradation and take a macro photo of both sides. That allows for later reading with magnification ... and no squinting ...
Last edited by rojarosguitar on Tue Apr 15, 2014 7:37 am, edited 1 time in total.
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