soundhole diameter

[peter havriluk]

I'm in the midst of making 'shrunken' (92% of original size) dreadnaught shaped guitar for a great deal of the time using a reduced copy of the Herringbone dreadnaught drawing that StewMac sells. Thinking about the sound hole....Martin's original is four inches in diameter. The shrunken drawing takes the diameter down to 3.68". I am assuming that using the shrunken drawing size won't be appropriate, but what guesses make more sense? three-and-three-quarters, three-and-seven-eighths, four inches (original size)? I've inferred that soundhole diameter influences the bass/midrange/treble balance of the instrument and tuning that balance is a mystery to me. Is it appropriate to use the 3 3/4" dimension initially, see how it sounds, and enlarge until it sounds 'better'?

Thanks,folks.

[John Parchem]

I like 3.75" my only concern with the 3.68" is if my hand still would fit. Like you say you can always make it bigger. Removing 1/8" will take you back to 4". A larger hole raises the frequency of the top resonance so only make it bigger if you think you need to raise the top resonance. What scale length do you plan?

[peter havriluk]

John, I'm making two instruments, I took a 25.34" fretboard and a 24.82" fretboard and lopped off the first fret on both. Roughly 23.9 inches and 23.65 inches. Both are slightly longer than my GS Mini. I think I have a good idea how Martin cooked up their Dreaednaught Jr.

[John Link]

Peter,

Martin once made a Clarence White version of their D-28 that featured a larger than usual soundhole. It garnered a lot of respect. As John P mentions, it is difficult to service a guitar when the hole is small, absolutely speaking. A number of forum members have experimented with an extra port on the upper side which has the same effect on the top's resonating frequency as using a larger soundhole. I don't recall anyone reporting this to have a negative effect.

Myself I like the "proportions" of the Clarence White model. I don't know exactly how large the opening is (someone who knows might chime in), but will upload a picture of a replica taken face-on, to give you an idea of how the diameter relates to the overall dimensions. The larger hole offsets the tubby look created by the shallow waist of the dreadnought design. In any case, accommodating future repairability is, I think, a good idea.

ClarenceWhiteModel.jpg (150.37 KiB) Viewed 3815 times

[Herman]

Peter,
A few years ago I made this M size Jumbo that was intended to be used in a loud surrounding. To make it less sensitive to feedback from a bass guitar nearby I made it stiffer, shallower and with a wider soundhole. It turned out to be one of my best sounding guitars. It has a 11 cm (4,33") soundhole.
That's about 10% wider than a normal Jumbo. So my ordinary advise wound be: It is not that crucial in your situation. You can try it either way. 4 inch or 10% smaller.
2ct Herman


Sound of this Jumbo