My second build was a CBG dulcimer for my kids. I cut out four one inch hearts, one in each corner of the box. The sound is not nearly as good as my first build. My first build had two 11/2 inch holes close to the neck end of the box. I've noticed that traditional guitars have the sound hole located toward the neck end. My thought is that then you would have this nice big chamber on the end of the guitar away from the neck for the sound to resonate in. Have those of you with experience found this to be true? At what point does the size of the hole(s) begin to take away from the sound quality?
Thanks for any input.
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I know that the material the box is made of has alot to do with the resonance. I build hand drums too, and a drum made of pine has a mellower sound than one made of a hard wood, like oak. Thickness of the wood, internal volume of the box, how the neck is run through the box,etc. Every variable has an effect on the overall sound quality. It would be fun to take a group of identical boxes and try different sound hole sizes, shapes and placement. Too bad I didn't win the drawing :)
I think that there is probably a lot more to this point than just where you place your sound holes. The type of wood and size of box would also impact it. I have a couple of CGB's with sound holes in the same place, but the tone is different on the two boxes (they both have the same scale length too). The main difference between the two is the boxes are different brands.
I think you could still do two holes, but the aggregate of the openings would have to be the right size. So two small holes or one larger hole. I'm sure that violin builders utilize the Helmholtz principle in violin construction and those typically have F holes. So I am not sure that the shape of the hole is the determining factor.
What I can see about the Helmholtz effect, putting holes in the four corners of the box would be counter productive. I see a lot of CBG's made this way, however. It seems like you would get the best sound from one or maybe two holes at only one end of the box. The article explains the Helmholtz effect by using the blowing across the top of a bottle description. A bottle with a hole in the bottom of it will not give the desired sound. A cbg with sound hole at either end of the box seems like it would do the same.
Tim
Replies
http://www.alcarruthluthier.com/guitars/corker.htm
Both of those articles address sound holes and "sound ports" holes on the 'side' of the guitar. Really good reading and scientific testing.
Tim