Playing the A string 9th fret tone is dead
 

Today i was surprised when playing the A string on the 9th fret to hear the tone without almost any sustain. Bought the Martin 2018 D28 a while ago but never played this note on the 9th fret. All notes on other frets have great sustain but not this note. How is this even possible?

What about the 14th fret on the low E?

Just tried it and is the same

Helmholtz resonance is around F# in some acoustic guitars. May be related to that.

One of the reasons I read AGF is so that I can be better prepared for Jeopardy! I just had to look up Helmholtz after that reply.

CK

Yes, it's a resonance with the guitar then. The guitar is quickly absorbing the energy produced by F#.

Did i buy a bad guitar now? Should i send it back or use my warrenty

Well if you play that F# a lot, you might want to return it.

I find that the open g is often deadish on many guitars. Very close to the f# mentioned above. I have always thought it's something to do with the way the wood resonates in dis-harmony.

Send it back. It's a clear cut workmanship issue. They're supposed to be a quality check on each guitar and this one slipped through. Must've been the last guitar before lunch or quitting time.

More responsive guitars are more subject to noticeable resonances. So that's a plus in a way. Try tuning the guitar to slight different pitch, or different gauge strings (different tension) or add a side port. :) Also how often do you play those particular notes?

Wow this does not make me happy... i will cal the store tomorrow... thanks

If it's a new guitar, I'd return it. None of my Martins have that issue, nor did the D28 I owned.

Resonance issues are fairly common. On a lot of "ES" style semi-hollows, the 12th fret G (G string) is often dead, and on fretless basses the 5th fret C (G string) can also die off really quickly.

There is (or was) a product called a "FatFinger" that you mounted to the head of the guitar to increase headstock mass, and this often can remedy the dead note issue. It can also just move it to another note/fret, and thus isn't always the best fix.

http://thumbnail.image.rakuten.co.jp...ms09/53723.jpg

The 'main air' resonance is often aroud F#, but it's the F# on the second fret of the low E string. The resonance that's troubling you, an octave higher, is probably the 'main top' resonant mode.

This is not a 'workmanship issue' on a Martin, since they make no effort to control this resonance directly. Also, this is one of the things that may change as a guitar 'plays in', and it certainly can change with variation in the humidity too. And, just to further confuse things, despite the names, the 'main air' and 'main top' resonant modes are, in fact, two parts of a 'bass reflex couple' involving (at least) the 'Helmholtz' air resonance and what you might call the 'real' main top resonance, neither of which occurs by itself at the pitches they take on in the assembled guitar.

It's the resonant modes of the guitar box and air that 'shape' the tone, and give each instrument it's voice. You can't get rid of them, nor would you want to, at least, not on an acoustic. Individual luthiers do try to gain some level of control over these, whether rationally or not. It can be done, to some extent, but the guitar is complicated, and wood is more variable than you might think, so it's not easy. Usually it requires some amount of tinkering after the guitar is together if you're particular about getting one mode 'right'.

There are a couple of things you can do about this. The fact that it affects the sustain of that one note argues that the pitch of the 'top' mode is pretty close to that of the note, so changing the mode pitch is a way to address this issue A simple way to do that would be to alter the mass of the bridge by swapping in some different pins. Usually production guitars ship with some sort of plastic pin, and those are the lightest, so anything you put in there will add some mass and drop the top mode pitch. Plain plastic pins run around 3 gm/set, while ebony ones go around 5gm, and bone/ivory will be more like 8-9gm. Sometimes even a couple of grams can make enough difference to be useful. Pins are cheap enough, but you can also add mass by sticking on a wad of poster adhesive, which is even cheaper, and easier to do (and undo!).

Most of the other ways of getting this under control are a bit more invasive, involving things like shaving braces to alter the top stiffness or removing some mass from the bridge. All told it's better to try the easy things first; sometimes they work as well as anything, and if they don't you're not out much, and haven't voided the warrenty.