[quote name='iiipopes' timestamp='1369712907' post='2091844']
It's not just the string excursion. It's the mechanical impedance of the neck. I have a Gibson J45 which I really enjoy. When I first got it, I was very careful to set it up properly. As I tightened the truss rod to a point of proper relief, it felt really, really good, and it appeared that it could go just a little bit straighter to make the action even better. But that last 1/4 turn of the truss rod damped down the vibration of the entire instrument too much, and the entire instrument lost its resonance. I backed the truss rod back off that 1/4 turn, and all the tone and resonance came back. I left it there, even though the action could, in an abstract sense, be even lower.
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Its interesting isn't it how little adjustments can affect the whole instrument. I've backed off the truss rod on both basses now and they sound better, even though as you say, the action could be lower.