The two most common tonewoods used for acoustic guitar soundboards are Spruce and Cedar. They each have very distinct tonal qualities and have a profound effect on the overall sound of the guitar.
Spruce is available in the following types: Sitka; Englemann; European and the most sought after of them all Adirondak, which is now becoming available again from managed sources. They all have a very good weight to strength ratio which makes them particularly suitable for guitar soundboards.
Soundboards come in a range of different grades and the insert below explains the system used to differentiate between the various grades.
In brief, “AAAA” is as good as it gets, about 1 to 2 percent of soundboard material grades out as master, with cosmetics (which are based on structural integrity) and runout differentiating this grade from AAA.
“AAA” is a good professional grade soundboard, with good cosmetic appearance and little if any runout. (Runout, commonly understood these days, was a little known subject before Bill Lewis wrote about it in his supply catalog of 1975.) We find that about 5% of tops fall into this category.
“AA” is a good grade, but may not be as perfectly quartersawn as AAA grade, or may have more grain variation, or some slight coloration. This is a grade that the US factories commonly use.
“A” grade is a decent top but few handbuilders ever use it, and few of the factories in the States use this grade. It’s more of an export grade, although one can find some nice tops in this grade if cosmetics are not of great importance.
(Courtesy of Allied Lutherie Ltd California)
Most of the Sitka spruce comes from Canada and Alaska, these days. This has become the traditional wood for steel string guitars simply because it is tough and strong, and it’s much more easy to get good quality wood from these large trees. As well, many manufacturers have problems with the softer surface of Engelmann spruce or Western redcedar. Their craftsmen have to be extra careful to avoid dings and dents from workbench detritus. That’s not to say that good sounding guitars aren’t made from Sitka, many prefer it to the other spruces. Comments are often heard about its good mid-range brightness and balance.
Considered to be the holy grail in top woods, Adirondack or Red spruce is one of the most difficult woods to obtain in decent quality. With a very high stiffness to weight ratio, it’s said to combine all the best qualities of the various spruces. Some of the best tops are Northern Red Spruce from the mountains of Maine and New Hampshire. Only prime logs growing without lean or bend, with centered hearts and regular growth are selected and tested for acoustics at the source with a sledge hammer and only the “singers” are used for musical instruments. The rest go to lower uses. In centuries past in the Italian Alps as the logs came down the snow-slews, the turners helping the logs around the corners would tag the ones that “rang” or “sang.” At the bottom those would go to the violin-makers. The best grades will have a sweet, clear voice or “Tap Tone”.
In the last few years Engelmann Spruce has grown in popularity. Many better known makers now use Engelmann in lieu of German Spruce since good Engelmann has many of the traits desirable in a good German top and it is more economical. In appearance it is like German Spruce, but unlike German Spruce, it seems to be more uniform in consistency. The tops are often more homogeneous looking with the early and late-growth rings being less distinct than those of Sitka. Like German Spruce, Engelmann has a beautiful ivory sheen and occasionally shows some pink streaking. It is also similar to German Spruce in workability. Although softer than German Spruce, it must be cared for as one cares for Cedar, i.e., keep a clean workbench.
Western Red Cedar
Used primarily by classic guitar makers, Western red cedar (Thuja plicata) is light and stiff, and can be rather fragile. Cedar is known for producing a loud, warm, and a mature sound almost immediately upon completion of the guitar. Occasionally interior or mountain red cedar, as it’s sometimes called, is available which is a little different than the coastal red cedar that dominates the market. It’s generally more colorful, and stronger and can be flexed without breaking.