pikolo wrote:
But how i do it ? I have a mic and visual analyzer. i taped the bridge on the top and fount the three basic tops(whre it makes a spike?) then what else?
I wholeheartedly agree with all the experienced builders above on there not being a formula (though Trevor might argue with that point to a certain degree
. That said, here's what I would do to give you the best chance at getting in the ballpark on your first try:1) Determine the species and dimensions of the target instrument, especially thicknesses of everything that makes up the body. Measure the top, back and sides to .001", braces can be to 1/32"
2) Buy some plans that match the target guitar shape and execute them using the dimensions and species you took off the original.
3) Put the target guitar on a stand, run a polishing cloth under the strings around fret 14, put your microphone a couple inches from the sound hole pointing straight into the hole and then record into your DAW while tapping firmly on each bridge pin. Do a freeze framed spectrum analysis and look for the lowest three peaks in the response during the louder portion of each noise. They should be nearly identical, other than volume. Write those down. they will be around ~100, ~220 and ~400 with the loudest one usually being the middle frequency. (note these are approximate and depend a LOT on the guitar design and size). If you can point out the body style I'll give you my target ranges to help identify these)
4) Once your guitar is done enough to temporarily bolt on the neck and put strings on it (before bindings or finish), do the same procedure with the microphone and DAW. This is where you can do a small bit of comparison and tweaking... but not much. The lowest of the three peaks is mostly related to the volume of air inside the body. You can't do much about that one. The next one will be the top of the body, which you can lower by sanding some wood off the edges of the top around the lower bought and maybe even a little toward the bridge. The third peak is the back, and you can do the same there. If you can reach them, removing wood from the braces of the top or back will also lower those frequencies.
Please understand I just reduced hundreds of pages of reference material and thousands of hours of experience down to a paragraph, so take it with a grain of salt. There are more holes than a good block of Swiss cheese in what I wrote above.
I suspect that's what you were looking for... but again, this will just be a way to get you close if you are lucky enough to end up with similar wood stiffnesses and grain orientations, and, and, and.
Best of luck!
![[headinwall]](./images/smilies/headbangwalluf8.gif "Mad")