As you carve you'll notice all the peaks going down. Only rarely they go up when you manage to get a better stiff to weight ratio than before. In any case i too start doing the Chaldni with the rough bracing and check constantly as i carve them and try to see how things develop. Often when the braces get optimized you'll notice the patterns improve as well. You might also see two adjacent modes merging into a single peak, with a different pattern.
Jaybird, spectrum analysis in itself is not very helpful on a free plate, because often some modes are missing; or you have extra; or you have two-in-one. You can easily decide which peak is the ring or whatever. But finding the peaks easily saves you the treble of sweeping the tone generator to the wits end. You see the peaks, set the generator to that frequency and see how it looks. You want those important modes in the 150-350hz interval to be at the right frequencies (plus minus 10-20Hz depending on what sort of sound you want, bassy, tight/bright, or balanced), and you want the shapes to look nice and clear. Sometimes one mode or another will be missing or sound weak, fortunately this doesn't seem to be the end of the Earth, the guitar will still sound OK.
Spectrum can be used in itself once you complete the guitar. It shows you the air frequency and the soundboard frequency with ease and if you think they are off you can do some things. But really its better to get it right before assembly.
The most important thing is to do it for every guitar and record the data.
Tip and rant: I sometimes see people leaving all sort of random overhangs around the top while claiming they do tap tuning or Chladni or whatever and I really cringe about it. A few mm extra of width can really change the tone or peak positions. You should either use the same exact width of overhang (not always possible if the raw top was just big enough) or better trim it to the exact final shape. Otherwise you really compare apples to oranges.
|
