Tom Anderson自己做琴的时候也遇到很多类似问题,我们看下Tom Anderson的理解:they are somewhat of a mystery. they seem to be more prevalent in mahogany necks than maple, but fender bass necks are famous for having them in a particular spot. my favorite acoustic guitar in the world has a horrible one at one note so i avoid that note. they are only really a problem if you are hanging on the note with nothing else going on. for chording and passing notes they're un noticeable.
so why do they happen? i've never heard an answer that i can agree with across the board. i think they show up more in very lively guitars as places where the whole guitar is inhibiting a particular frequency. i think that's why we see it in mahogany necks more. they are a more delicate piece of wood and i feel they have more harmonic stuff going on than maple. so we hear more inconsistencies in them. i have had necks with terrible dead spots on one guitar that worked very well on a different body. we took a neck off a cobra we built for stevie fryet because of a dead spot and put it on the black cobra that keith richards played for many years. my guess is that keith has never complained about a dead spot.
many have played around with different reinforcement products in necks to counteract it with varying results. in all my years of working with guitars i've not either before the build or after the build been able to "see" why a particular piece would be worse than another. obviously we discard lots of wood for lots of reasons and still see it happen. for the most part it is just that some notes ring a bit longer than others, not that a note is unusable.
we occasionally gets calls from people that sit around timing the sustain of each note on their guitars...
Dead spots will appear to some extent on every guitar. A couple of things you can try, is to loosen the neck bolts slightly, by about 1/8 of a turn while the guitar is tuned up to pitch. The string tension will re-seat the neck in the pocket and maybe pull it forward a bit. Then retighten the bolts. This may help. Also a slight tweak of the truss rod, either looser or tighter, can sometimes do the trick.
Sometimes lowering the pickups will help. Also a change in string brand or playing the note with some extra vibrato can help. Also adjusting the truss rod one way or the other can help. Check all of the hardware to make sure there is no sympathetic vibration absorbing the note.