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Old 03-25-2013, 02:38 PM
Alan Carruth Alan Carruth is offline
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redir wrote:
" I've never really 'got' scalloped bracing. "

It's all about the sound you're trying for.

The top of the guitar vibrates in several different 'modes' at different frequencies. the power and timbre of the guitar have a lot to do with the amplitudes and relative frequencies of these modes.

The one that produces the most actual sound is the 'main top' resonance, where it's moving in and out like the cone of a loudspeaker. Most speakers have a (more or less) rigid cone and a 'soft' rim, but you can't go too far in that direction on a guitar top, simply because it has to withstand the bridge torque over the long term. How well the top moves, and how much air it can push in the process, is thus a function of how stiff it is in different places.

A lot of makers thin the edges of the top to get it to move more. This works, but,again, you can only go so far. Modeling that has been done, by Evan Davis, and maybe others, has shown that it produces more sound to make the center of the top flexible, rather than the edge. It's a nice trick to make the center as flexible as you can, and keep it as stiff as you need, but it can be done.

What happens in that case is that the bridge moves a lot, extracts the energy from the strings in a hurry, and turns it into sound. You get a strong attack, with a lot of fundamental, and plenty of power.

The peaks near the outside ends of the braces serve to stiffen up areas of the top that move more in higher order modes. These are not as efficient at producing sound as the main 'loudspeaker' mode, and suppressing them and moving them up in pitch helps emphasize the fundamental.

'Tapered' bracing, that's higher in the middle and low at the edges, works the opposite way; bringing up more of the higher partials, and giving more sustain.

Nether of these is intrinsically 'better' than the other, they're just different. Scalloped bracing tends to work well for some styles of flat picking, and for accompaniment, where you want the 'punch' to come through and don't want a lot of sustain to muddy things up. Fingerstyle players tend to like the even and sustained sound of tapered bracing. 'Straight' bracing fall somewhere in between, and can either bridge the gap or leave everybody cold, depending on how well it's done.
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