On Scalloped Braces

Everyone seems to make such a big deal about them, but what are your thoughts on scalloped braces?

======================

I don't know what justification is advanced by builders who scallop their braces: I don't. Maybe you should ask them. I suppose they would reply, "Martin used them on guitars made during the 20s and 30s, and since those guitars reputedly sounded so good, presumably it must have been the scalloped braces." Sounds like lore, doesn't it?

Few people know that actually, those early guitars were originally braced for gut strings, and when decades later people swapped steel strings onto them, their tops eventually collapsed from the extra tension. But boy, they sure sounded great before they collapsed!!

The peculiar scallop shape, it seems apparent to me, must have originated as a result of an early voicing technique where (in the days when luthiers worked in factories, and were not just machine operators) builders reached inside through the soundhole with finger planes and removed material judiciously from the braces, in stages--and progressively listen to the changes after restringing, and stopped when they felt the compliance was "right."

There's nothing magic about the scallop shape itself, just that it was the result of the process of using finger planes to remove material through the soundhole. At least that's my best guess. But as it happens, that peculiar shape decades latered engendered enough lore and mystery to subsequently drive aspiring luthiers crazy trying to decipher its significance. I have been asked that same question by many of them.

Large, stiff, disappointing guitars are today "strutted" by technicians who reach inside through soundholes with finger planes to remove material from their "struts" to improve the sound. The result usually is to "hot rod" the guitar by making it sound somewhat louder and a bit deeper-voiced...while potentially hastening it's demise. The guitar survives only if the braces were way too large to start with or if the the strutting was done with great restraint. It takes an experienced eye to sense how much is too much.

The string's signal is nothing more than minute and rapid changes in tension (dynamic stress) amidst the constant background string tension (static stress). So the problem is to construct the top in a way that adequately supports the static stress without hindering the dynamic stress. It's the guitarmaker's dilemma: that the soundboard is really a trade off between structure and tone. If the brace heights are left high, the soundboard will resist the 200 lbs of steel-string tension with no problem at all, but with a price to pay insofar as the acoustical range that results: invariably a tight sound or a limited tonal response. Reducing the brace heights increases the compliance of the top to a wider range of signals coming from the strings and a more satisfactory acoustical response, but with a price to pay in its architecture. The builder is truly expert when he derives a sense of structure sufficient to dimension the top thickness and brace heights to achieve an optimum--say, minimally adequate structure.

So, the secret is not in the peculiar contour of the braces, it's in the acquired skill of the builder that senses the minimal structural requirements of the instrument and responds correctly when removing material. Note that Martin now again offers "scalloped braces"--as a marketing ploy, I suspect, because no one in the factory is graduating braces. They are likely to be using thicker, stiffer tops to hedge their bets, and make it a point to insist that low tension strings be used.

Can the X-brace Be Improved?

Would you agree that the "half-lap" joint on the x-brace is a weak spot, both structurally and sonically? I was thinking of making an X-brace of two pieces of curved wood rather like two letter C's back-to back, they would have a flat spot where they meet for gluing, and possibly pinning together with little hardwood dowels. (I’d like to send you a small diagram) I think this would give the x-brace strength and continuity, have you ever done anything like this?

I think you're asking the wrong person: I'm not an armchair guitar tinkerer. I'm not inclined to "improve" the guitar by imagining what may be flaws in it's traditional design and then imagining ways to remedy it. My approach is optimize the givens, not change them. But as the saying goes,"I'm a vegetarian, but I'm not going to take the meat off your plate." So you're welcome by me to go ahead and try your scheme and see for yourself.

But you make two assumptions: that the current x brace scheme needs more "strength" and that "continuity" is somehow a goal. Yet some vintage x-braced Martins I've seen dating back to the twenties have carried the string tension load for almost ninety years without distortion. And have you considered it possible that one stiff x brace and one weak x brace is precisely what makes a steel string guitar sound the way it does?