Question for Alan Carruth

Please put your pickup/wiring discussions in the Electronics section; and put discussions about repair issues, including fixing errors in new instruments, in the Repairs section.
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Brian Evans
Posts: 873
Joined: Sat Aug 30, 2014 8:26 am
Location: Tatamagouche, Nova Scotia

Question for Alan Carruth

Post by Brian Evans »

Hi Alan, I just posted about my latest archtop (Experimental guitar thread). I've been playing it for a few hours, found it to be remarkably even in volume up and down four octaves, and thought I would find what I call the fundamental tone of the box. I sing into the soundhole and find the lowest note (that I can sing) that makes the box resonate strongly, in this case a low F. My other archtop resonates around a mid D (fourth string open). It has a dead note there that disturbs me sometimes, so I tune down to miss it. This new guitar resonates at a low F (sixth string, first fret) and has no dead notes that I can find, very even. I then noticed that it's "drum tone" is very close to that note, and the drum tone (damp the strings, strike the top like a drum, basically) of the other guitar is also quite close to it's resonant note. I wondered if you had thoughts on this sort of thing, and how to influence it in the build cycle. I am really exceptionally pleased with the evenness and tone of this most recent guitar.

Thanks in advance, Brian

Alan Carruth
Posts: 947
Joined: Sun Jan 15, 2012 1:11 pm

Re: Question for Alan Carruth

Post by Alan Carruth »

'Evenness' is not a simple thing, and I'm not sure I understand it very well physically. I strongly suspect that the way the guitar works in the upper frequency range makes a big difference, and that's hard to characterize and even harder to control in some respects. I've been pretty lucky in getting an 'even' sound in the past few years, and it's been pretty consistent, so it's not a fluke, but I can't say I really understand it yet.

That 'air' mode is lower than I thought it would be. The combined top and side hole area is pretty large. OTOH, it's 'way up in the corner, which drops the pitch a lot.

The 'air' and 'top' modes couple quite strongly; to the point where it can be hard to say just what each one 'really' is, or would be in isolation. You can get pretty close with the 'top' mode by completely blocking the soundhole(s) and tapping the top. This also cuts out the 'masking' effect, where the ear assumes that the 'top' resonance is actually a partial of the 'air' mode, and blends the pitch.

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