I need some of you really knowledgable luthier to help me with this, I think. I've bought and re-sold a lot of guitars lately, looking for that perfect guitar for me, and just as a fun hobby. Every one of them has had a note that "thumps" somewhere on the fretboard on the D string. I'm convinced if you pick up your acoustic steel string and fret each note of the D string and play it with your naked thumb (no pick,) you'll find it on your guitar, too. Hard to describe, but here are a few attempts. It sounds very harsh on the initial attack, instead of starting with a nice beautiful ringing, or even singing, note like the rest of the notes on your beautiful, expensive guitar. It's almost as if you're hitting the guitar top instead of plucking a string. Like as soon as you pluck that note, your guitar body spits it back out the sound hole without even trying to resonate it through the wood. Like the air mass inside is suddenly mado of concrete and just flat will not allow that note inside the guitar body. When you pick softly, it's louder and more percussive than the other notes you pick. I do a lot of fingerpicking, and that note jars me and sounds ugly every time. I need to know if it can be fixed or improved, or if not, is there a way to make it move to a different fret a good ways up the neck. On 14 fret guitars Grand Auditorium,) it's most often on the 4th fret of the D string (though I have a solid Mahogany one where it's the 3rd fret,) and on Taylor 12 fret guitars, it's often on the 2nd fret of the D. It's not the strings (or a particular string) as I have often changed sets, diameters, and even brands and materials of strings to make sure that's not it. It's not something wrong with the guitar. I've experienced it on at least 8 different Taylor, Takamine, Alvarez, and Jasmine guitars, all with proper truss rod adjustment, no nut or saddle issues, etc. It's not the way I fret the note. It happens even when I just put a capo on that note and pluck it. It's not the way I pluck the string. It doesn't happen on other strings, or other frets of the same string, when I pick in the same way with the same thumb. Using a pick lessens the effect, but once you've found it you can still hear it even when you use a pick. I think it has something to do with the inherent resonant frequency of each guitar. I 've had a couple of people tell me it's that "blowing over a Coke bottle" effect, (the Helmholtz Resonance.) Believe it or not, one time I even tried putting a bath towel in the body os a guitar trying to change the air mass, but it didn't change anything. And the Helmholtz Resonance is not my problem, anyway. I've come to understand that the Helmholtz is a good thing that helps guitars project the lower frequencies, and on many steel string guitars is most noticeable at the pitch of the open A string on the guitar. (Hum into your guitar at that A pitch, and the air mass will sing back to you.) I can hear the Helmholtz go away and come back again by playing the open A string and moving a piece of cardboard or thick paper over the soundhole and back off of it. But moving that paper over the hole does not eliminate my "thumping" note somewhere on the D string, depending on the guitar. I read an article that talked about "coupling," that is, how well all the components of a guitar (i.e., saddle, bridge, top plate, bracing, air mass, etc.) work together to project sound, and said if the ckoupling is "too good," it can cause harsh and bad sounding results. I suspect that what I'm hearing is a place where, on these well made guitars, the coupling is unavoidably so good that all the energy of the string is released too fast-almost all at once- and produces my thump that I'm hearing. I've had to return 3 Taylor 12 frets because the "thumping" note in the 2nd fret of the D string is in a lot of first position chords and just ruins an otherwise nice fingerpicking song. Please help me with how to fix or move this problem to a different fret. I've had several beautiful guitars I just couldn't keep because this "thumping" note bothered me so bad. I'm new to this site and hope this is an acceptable kind of topic. Forgive me if not.