What kind of wood is best - May 2002
The tonal characteristics of an instrument come from both permanent & modifiable physical attributes. The type of wood is just one of the permanent attributes of an instrument– a characteristic that interplays with the other attributes (both permanent and modifiable) in creating the intrinsic voice of your instrument.
Tradition dictates wood choice in violins: spruce for the top & maple for the back, sides & back. Early on, some luthiers used poplar for the back & sides. Now, some builders occasionally use walnut or cherry. Fiddlers, while prone to choosing maple/spruce, are more open to non-traditional woods. But few violinists want anything but the bright & projecting maple/spruce combination. This combination creates bright projecting voices in guitars & mandolins too. And maple rims, necks & resonators on banjos also gives them bright voices. All-maple guitars (no spruce) are extremely bright.
At the extreme other end of the tonal spectrum are guitars with mahogany back, sides & tops. These guitars have thick, sweet, throaty voices that have more midrange tone & fewer overtones than guitars of other tonewoods. Because guitars exhibit the greatest diversity of wood combinations of the traditional acoustic stringed instruments, they also have the greatest range of possible voices. Guitars made of mahogany & spruce have sweet, projecting, balanced voices with few overtones. Koa/spruce & koa/koa guitars are very much like mahogany/spruce & mahogany/mahogany guitars. Guitars made of rosewood & spruce tend to have bass-rich, projecting voices with complex overtones. A walnut/spruce combination has a bright, projecting voice with more bass than maple/spruce & fewer overtones than rosewood/spruce. These general trends in tonal quality with respect to wood are true for other instruments as well, but instruments other than guitars typically have less variety of woods (we have noted that Mid-Missouri’s rosewood/spruce mandolin has a very projecting, sustaining, complex voice).
In addition to spruce, cedar is a common tonewood for the tops of both steel & nylon string guitars. Cedar as a top-wood tends to “fatten” the sound relative to the tone that spruce produces. This tendency is true for instruments with backs of cherry, rosewood, mahogany, koa & other tonewoods & for instruments with various body sizes & shapes. The tonal character of wood comes from its density, stiffness & other measurable physical properties. Acoustic engineers & material scientists have done extensive research to determine the properties of various woods - measuring the velocity of sound, the attenuation of sound, the harmonic frequencies of sound, & numerous other aspects of sound traveling through wood. Each type of spruce (Sitka, Engleman, Adirondack...), rosewood (Brazilian, Madagascan, East Indian...), mahogany, koa....has its own unique acoustic “signature,” that – in combination with the signature of the other permanent & modifiable attributes of an instrument – create its voice.
In addition to wood type, permanent attributes that affect tone, include the body size & style of the instrument1, the internal bracing pattern & the type of finish. Modifiable attributes involved in an instrument’s voice include type & gauge of string2, the material of which the nut, bridge/saddle & tailpiece are made, the player’s technique & amplification methods. So for each wood or wood combination, an array of influences color the specific voice of each instrument. The “best” wood will depend on the kind of voice that the player seeks & how the woods combine with other permanent & modifiable attributes.