I've been testing my hand built box with a tuning fork, looking for bridge placement sites. I have found a few areas that vibrate very well with nice tone. Next question would be, where to place the sound holes, since some of these placement sites are mirrored on the opposite end of the box.
One spot is 1.5" away from the longitudinal edge. The surprising part is that there are two bands that vibrate well, both at almost exactly 1/3 of the box length, so, one at 1/3, and one at 2/3, with sound production better towards the ends than at the center. I'm intrigued by that 1/3 value, thought the sweets spots are not exactly aligned on opposing sides of the box. Maybe off by 1/4".
When I place the tuning fork at any of these positions, the other points vibrate well. At the center of the box is sort of dead.
Question is, would these vibrating bands also be a good place for a sound hole, or, should I let them resonate and add to the sound, and place the sound hole offset from there.
Box is 8x12x3, so, bands are at 4" and 8" of length.
Must be a standing wave going on. I used an A turning fork. Hope other note values don't shift the optimal points.
Please see attached photo.
This kind of stuff always interested me. What Billy says makes sense. My best sounding cbg's bridge tend to be 1/3 or even less on the end of the body. As an artist I'm picturing the cbg surface as a pool of water and the bridge as an area where you would drop a stone or pebble into the water and forming ripples or waves. having the bridge not dead center should give more variety to the waves and allow some to travel further on the body before cancelling each other or dying out. Just my observation/imagination getting away on me again!