Quote:
Originally Posted by Left of Sam
EG, if I tapped along the cross dipole and thought it was too high freq, would I shave right beneath where I tapped?
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That is an interesting question to me because I can say with absolute certainty: "I don't know."
The cross-dipole is a higher-frequency mode. It describes a motion of the top from side-to-side at some resonance frequency that is higher than the "main top."
How do you excite that mode? Probably not so well by tapping, but I haven't really explored that.
How do you shape that mode? My understanding is that it's pretty brute force: you can add bracing to deemphasize that mode or you can "free" that mode to do its thing. Not sure how you shift the frequency per se.
To get a sense of what parts of the guitar are responsible for which resonance frequencies, I do a pretty simple test:
1) play a note
2) mute parts of the guitar to see which area has the largest effect
For example, you'll see that the lower bout has the largest effect on bass by muting that area with your hand when you play a bass note.
Try the same when you play a treble note, and there's not a big effect. But mute the area on either side of the sound hole or perhaps even the upper bout above the sound hole, and you may experience a fairly large high-frequency effect.
I haven't really experimented with shaping that higher-frequency response. If you do, let us know what happens.