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Acoustic guitars are simply air pumps. In this regard, they’re no different from drums: The more air they excite, the more sound they give off. A guitar’s top is the single most important piece of wood in the instrument, and it works exactly like a drumhead. When making a top, the most important factors are what wood to use, its final thickness, and most of all, the bracing. For luthiers, bracing is the single most hotly debated area of guitar making.
Top bracing has everything to do with controlling and shaping sound, and—contrary to popular opinion—rather little to do with keeping the guitar top together. If a guitar lacks bracing, it will not fall apart, but its relatively flimsy top will vibrate chaotically, much like a pool of water during an earthquake, and its sound will be flat and harsh. To vibrate coherently, a top requires an organizing principle, and that’s what the bracing provides. Is there a ”best” bracing system? No. But a few systems have proven themselves over time.
Proven Bracing Systems
Most steel string guitars use the “X” bracing that was more or less invented by the Martin Guitar Company as early as the 1850s (Fig. 1). Spanish guitars—that is, guitars strung with gut or nylon—almost universally have one version or another of fan bracing (Fig. 2).
Other systems include ladder bracing (Fig. 3), such as those found in the inexpensive Harmony guitars that were extensively used to play early blues (so much so that their sound has become identified with that music), and lattice bracing (Fig. 4) which was first put on classic guitars and is now sometimes found on steel-string models. More recently, Kasha bracing (Fig. 5), the brainchild of Dr. Michael Kasha, a guitar aficionado from Florida, has begun appearing on steel-string acoustics. Each of these patterns is capable of infinite variation, and unless radically altered, each is capable of producing a more-or-less identifiable sound.
A few other oddball bracing patterns, such as asterisk bracing, can be found on the occasional guitar, but none of these has caught on in any significant way.
Spanish guitars, for reasons of size, design, and stringing, naturally offer a bassy sound, but not great high-end response. When building a Spanish guitar, the guitar maker has to put a brilliant treble response into the soundbox. This requires skill and experience. Those building steel-string guitars face the opposite challenge. By virtue of its size, design, and stringing, the steel-string guitar naturally produces a good bright sound, but not a good low end, and therefore the luthier must elicit a strong bass response out of its soundbox. This too requires great experience and skill.
None of this matters much if a guitar is designed to be amplified. Using EQ, you can make a mediocre guitar sound pretty good. But if you’re a guitar maker or an acoustic enthusiast who’s serious about unamplified sound, the soundbox’s voice becomes an area of great fascination.
If you’re contemplating buying a pricey acoustic guitar, you owe it to yourself to learn something about how the instrument works, and also how to tell a good guitar from a mediocre one. Google some guitar makers, identify those who seem to know what they’re doing, and seek out one or two for consultation. Also read up on the subject. And remember, forming an opinion based on glitzy advertisements is the least effective path to an education.
A professional luthier since the early ’70s, Ervin Somogyi is one of the world’s most respected acoustic-guitar builders. To learn more about him or his guitars, visit esomogyi.com.