|
As Antonio Torres (1817-1892)
proved over a century ago, when he made a guitar with papier-mâché back and
sides, the top is critical to the guitars sound. Of the several "tone
woods" available, spruce is the most widely used. There are several
varieties of spruce used in building musical instruments. By far the first
choice for top quality classical guitars is Alpine spruce (picea abies),
commonly called German spruce. This European spruce, which comes
from thinning forests in Switzerland, Germany, and the former Yugoslavia, has in
recent years become increasingly hard to come by. Although Sitka or Englemann
spruce from North America is inferior to European spruce for classical guitars,
it is widely used to construct steel-string guitars because its slightly
different fiber structure helps dampen the harsh harmonics produced by steel
strings. Hokkaido spruce has been used Japanese makers in their guitars.
 In the 1960s, high quality German
spruce became increasingly expensive and difficult to obtain. Jose Ramirez III
(1922-1995) began to explore the possibilities offered by Western red cedar (thuya
plicata), commonly called Canadian cedar. Its close, straight grain, dimensional
stability even under changing temperature and humidity, and tonal responsiveness
made it an ideal substitute for spruce. Following Ramirez, many famous luthiers
such as Ignacio Fleta (1897-1977) and Daniel Friedrich (born 1932) began
building guitars with cedar tops.
Although some guitar makers are
able to achieve good results with cedar, others cannot make it work for them. In
my opinion, the choice between spruce and cedar (other things being equal) is a
matter of taste, much like the difference between vanilla and chocolate ice
cream. Cedar guitars tend to be more responsive to low-frequency
resonance's, and so are often sweeter, mellower, yet makers are also able use it
to produce bright, clear guitars. On the whole, I find that cedar guitars have a
darker tonality, and that the sound is less direct, more enveloping than spruce.
The sound of a well-aged fine spruce top has an unmatched openness, clarity,
directness, and edge like an arrow.
 One of the raps directed at guitars
with cedar tops is that unlike those of spruce they do not improve with age. The
other spin, of course, is that they are responsive from the start, and one
doesn't need to play them in for years to achieve the openness of aged spruce.
This does not mean, of course, that a poor sounding instrument will become a
good one with time. The rap against spruce is that it is much more subject to
changes in humidity than is cedar. This is precisely why it is so vital that
such woods be well-aged and properly dried.
From the start, the older the
spruce used by the maker, the better. Spruce is a very hydroscopic wood,
that is to say it tends to absorb the same degree of humidity as the surrounding
air, breathing moisture in and out with changes in humidity. Wood cellulose is
of two types: one which is amorphic and absorbs and returns humidity; and the
other which is crystalline and does not absorb humidity. Once wood is cut, and
begins to dry out returning the moisture it absorbed in its life to the air, the
crystalline form begins to replace the amorphic form, reducing its tendency to
absorb humidity, and increasing its rigidity and capacity to vibrate with
greater amplitude. In short, as it slowly ages and dries, its tonal
characteristics improve. While there are wood suppliers who guarantee the woods
they provide have been aged 50 years, woods once they reach their optimum
of dryness, will not improve no matter how much time passes. Air-drying is
preferred by luthiers to kiln-drying methods as it allows time for chemical
changes to occur which "cure" the wood. If woods are properly
air dried, wood may be seasoned in as little as three to five years. Luthiers,
however, may cure their tops for much longer-- often twenty to thirty years.
The quality of a top is judged by
three aspects of its wood's grain: straightness, density, and medullar rays. The
straightness of grain is very important in determining sound quality and timber.
The wood grain should be totally straight with each grain parallel to the
others. Since sound travels along these long fibers, any deviation from straight
grains reduces its strength. Density is likewise important. The great the
density (number of grains per cm) the finer the top. Here it is important to
observe whether or not the density is uniform. Irregular spacing indicates that
the wood has not been cut along the grain, and is of an inferior grade.
Generally, in premium grade woods the distance between grains is less than 2 mm.
One of the feature's of fine spruce tops is the presence of medullar rays,
fibers which grow at right angles to the grain. While their natural function in
the wood is to circulate starch and resin, they improve the tonal quality of the
soundboard by providing links between the long fibers of the grain. Light
medullar rays also may be found in cedar, but they are not as marked nor do they
seem as important to sound as for spruce.
In recent years, some guitar
factories have attempted to imitate the appearance of fine instruments by
building instruments with laminated tops. Naturally, they sound like the plywood
the are made from. Buyer beware. Make sure the instrument top is made of solid
wood.
Next : Wood for back
|
