Tone Wood

Spruce and Top-Wood Varieties
Occasional Top Tonewoods
Body Tonewoods
Grading Top-Wood for Musical Instruments
Glossary of Terms

Spruce & Top-Wood Varieties:

Engleman Spruce – Picea Englemanni

Silver spruce
White spruce
Mountain spruce
Columbian spruce

Growing Range:

Temperate Northern Hemisphere: the interior wet-belt region of British Columbia. The trees like cool damp climates and moist loamy soils. The trees extend from Alberta and British Columbia southward through Nevada, Utah, and Colorado, into Arizona and New Mexico; the southernmost populations in Arizona (Chiricahua Mountains) and New Mexico (Sierra Blanca) are ssp. mexicana, which otherwise extends southward into both the eastern and western sierras of northern Mexico.

The Timber:

Trees grow up to 36″ caliper and mature trees can reach 150 feet tall. Trees can reach 300 years old. These trees are fast growing with grain that is straight and fine, creamy white or very light yellow color with little contrast between heartwood and sapwood.

Strength:

Lightweight: specific gravity of 0.34 to 0.38 with 13 to 24 lines per inch. A high strength-to-weight ratio and above average in stiffness.

Shrinkage:

Reasonably stable.

Supply:

Available but harder to find in high grade sets due to over-harvesting for paper pulp, and other general uses.

European Spruce – Picea abies

German spruce
Italian spruce
Swiss spruce
Carpathian spruce
French spruce
Jugoslavian spruce

Growing Range:

As with most spruces, these trees naturally and historically live in cooler, higher elevations, preferring lots of moisture and rich, somewhat acidic soils. The original range includes most of Europe outside permafrost from the Scandinavian arctic down to northern Greece, west to the French Massif Central. The northern range extends off the map towards the Urals where it meets and hybridizes with Picea obovata. It has been planted all over the planet by now, and adapts to a wide variety of soils and climates probably because it survived the Ice Age. The largest known example of one is in a park just west of Moscow, though this is an anomaly, since these trees typically don’t live longer than about 200 years. Tiny remnants of the pre-glacier and pre-human-impact older range are found in the Pyrenees, down the center of Italy, and along the south coast of the Black Sea, in northern Turkey.

The most southerly of the three ranges lies in France, Switzerland, Italy and a bit of Austria and Slovenia – in other words, the south face of the Alps – trailing down through the mountainous parts of Bosnia, Herzegovina, Serbia and Montenegro, with remnants in Bulgaria and the Balkans. This is the part of the historical range that escaped glaciation and provided the reservoir for the reintroduction of the species back into the northern ranges after the glaciers retreated.

The spruces of the lower range were until recently taxonomically classified as Picea excelsa. Many sources still refer to that as a species, and some refer to it as the German botanical designation for Picea abies. In any case, Picea excelsa has now been folded together with Picea abies as a single species. If you see the term Picea excelsa, it’ll be in – or referenced to – older literature. The trees in the lower range are also still classified by some botanists as a subspecies called Picea abies v.excelsa. It is debatable if this is a wise designation, as the only thing distinguishing this so-called subspecies is how it grows in that environment. A propos, this is the range from which the Cremonese master violin makers and the lutherie elite of Europe have historically gotten their wood.

The middle range on the north slope of the Alps and across southern Germany and east into Poland and Czechoslovakia contains Picea abies, most of which has been reintroduced since 1800. Because of the thorough exploitation and devastation of the forests through the end of the 18th century and the enormous timber demand in early industrial times, the natural forests, which had already regrown after the retreat of the glaciers, were eliminated and eventually reborn as artificial forests. Ironically, the seed stock for the reintroduced Picea abies came from the relatively unscathed Scandinavian range, which had itself re-established itself from that southern reservoir after the last Ice Age.

Today Picea abies comprises 35% of the tree cover in Germany, and most of that is in managed forests. Among the other major conifers in German forests are Picea glauca, an American import, and Douglas fir, another American import. These trees have been grown in Germany for a very long time (see below). It is an irony that over the last fifty years or so, forest management in Germany has increased forest size considerably (in stark contrast to the rest of the world) but its air pollution is so extreme (largely blowing in from other countries) that the forests are very unhealthy and the yield from that acreage is decreasing. Picea abies is acutely vulnerable to the pollution problems, notably acid rain.

Moreover, if you have ever spent time talking wood with instrument makers in Germany, they will chuckle and tell you they consider “German spruce” not just a misnomer but an unlikelihood. They generally get their spruce from farther south, in Italy, Slovenia, Switzerland or France. This has always been the source of the best lutherie spruce. As Horst Grünert, a bass and cello maker in Penzberg, Bavaria, once cheerfully told me, he’d go right out with his chainsaw and get the rare spruce in Germany if he could find it, but he said that for all intents and purposes, it had been extinct in Germany for several centuries (again, see below). The spruce I was seeing all over the Alps was, he said, good for fence posts and pulp, and that’s what it was farmed for. Outside of parks and so on, I never saw trees larger than about eight inches either.

German spruce sold to the lutherie world is often spruce sold by German dealers, and whatever species of spruce it actually is tends to come from a variety of sources, including a certain amount historically imported from the US and Canada. Engelmann spruce, for example, is very popular among luthiers and for decades has been exported to Europe where it has been sold back to Americans (among others) as, you guessed it, German spruce. And because of the lutherie trade, spruce from anywhere in Europe is pretty much identified now as German spruce.

Unless you cut the tree yourself or can be absolutely certain where that tree was harvested, it is probably safest to just call it spruce. If you’re certain it grew and was harvested in Europe, there’s no point in getting your turban in a twist over common names. If someone says German spruce, just think, “OK, Picea abies, or European spruce.”

The above was excerpted from Paul Hostetter’s website: www.lutherie.net

The Timber:

Strength:

Lightweight: specific gravity of 0.42. A high strength-to-weight ratio and above average in stiffness.

Shrinkage:

Reasonably stable.

Supply:

Available due to its broad growing range.

Black spruce – Picea Mariana

Bog spruce
Eastern spruce
Swamp spruce
Epinette Noire

Growing Range:

Canada & Northeastern North America.

The Timber:

Trees grow up to 20″ caliper, slow growing and straight, fine grained, nearly white with little contrast between heartwood and sapwood.

Strength:

Lightweight: specific gravity of 0.38 or equivalent of 28 pcf. Stronger than white spruce: medium in strength and above average in stiffness.

Shrinkage:

4.1% radial and 6.8% tangential, 13% volumetric.

Supply:

Plentiful.

Adirondack “Red” Spruce – Picea Rubens

Red Spruce
Appalachian Spruce
Eastern spruce
Yellow spruce
He-balsam
Epinette Rouge

Growing Range:

Temperate Northern Hemisphere: Throughout Canada’s Maritime Provinces and as far South as North Carolina, US.

The Timber:

Trees grow up to 24″ caliper (57″ maximum), straight, fine grained, nearly white or cream in color with little contrast between heartwood and sapwood.

Strength:

Lightweight: specific gravity of 0.37 or equivalent of 27 pcf. Stronger than white spruce: medium in strength and above average in stiffness.

Shrinkage:

3.8% radial and 7.8% tangential, 11.8% volumetric.

Supply:

Ample.

Sitka Spruce – Picea Sitchensis

Coast spruce
Tideland spruce
Yellow spruce
Menzies spruce

The name came from Sitka Island (now Baranof Island) in Southeastern Alaska where the species was discovered and named by Europeans in 1892.

Growing Range:

Temperate Northern Hemisphere: hugging the Northern Pacific coast, seldom growing inland more than 50 miles. The tree grows from sea level to approximately 5,000 feet. It ranges from Southern Alaska (Kodiak Island and Cook Inlet) through Southeastern Alaska down through Northern California.

The Timber:

Trees grow up to 36″ to 72″ caliper and mature trees can reach 175 feet tall. Trees can be 700 to 800 years old. One of the largest trees documented is 16.7 feet caliper and 216 feet tall. These trees are fast growing with grain that is

straight and fine, creamy white or light yellow color blending to pinkish-yellow heartwood with little contrast between heartwood and sapwood.

Strength:

Lightweight: specific gravity of 0.37 or equivalent of 28 pcf. one of the highest strength-to-weight ratios and above average in stiffness.

Shrinkage:

4.3% radial and 7.5% tangential, 11.5% volumetric.

Supply:

Dwindling due to limited areas for growth and over-harvesting for paper pulp, ladders, oars, masts, boat planks, turbine blades and windmills.

Spanish Cedar – Cedrela Odorata (Fragrant cedar)

Cedar

Occasional Top Tonewoods

Koa (Acacia koa)

Location: Hawaii

Traditionally koa tops have appeared on small bodied Hawaiian guitars and ukuleles but also appears on dreadnoughts and custom guitars. Koa produces a bright treble response with less volume than spruce, but the loss in volume can be overshadowed by the extreme beauty of the grain. Koa tops are available on special order and custom instruments.

Genuine Mahogany (Swietenia macrophylla)

Location: Brazil

Mahogany was first introduced as a topwood in 1922 on the inexpensive guitars. Tonally, mahogany has less projection than spruce and producing a subdued response that can be crisp and delicate with an emphasis on the midrange.

Walnut (Juglans nigra)

Location: North America

Highly figured walnut tops, matched with walnut back and sides can be custom ordered from many builders. They can have a rich, warm bass with plenty of crispness on the mids and trebles. Walnut offers the beauty and visual impact of an all-koa guitar, but at a lower price. Coloration is dark brown and can have a lot of figure.

Body Tonewoods

Tonewood refers to wood with acoustic qualities used to make musical instruments.

Instruments are generally made of a number of different woods, each used for their special tonal, aesthetic or structural qualities. The wood used for the vibrating top of an instrument, for example, is selected for its directional stiffness and ability to produce pleasant sound. This section is intended to address the woods used to create the sound box of an instrument: the back and sides.

See the section: “Instrument Tops / Soundboards” under the Wood heading for descriptions of top woods.

The following are general descriptions of the tonal properties of some of the most widely used woods for acoustic guitars.

Disclaimer: We need to state the obvious here: Wood is a natural material and no two pieces are exactly the same even if they are drawn from the same trunk. The way an instrument sounds is determined by the Luthier, the design, the size, the bracing and the tonewoods – arguably in that order. The use of a particular wood will not assure a certain ‘sound’. As with all natural materials, the best we can do is identify patterns of behavior that help contribute to the choice and selection of woods for an instrument. In many cases, an equally valid way to choose the wood for the sound box on an instrument is by the way it looks: is it beautiful? The choice of the Luthier – Now THAT will have a direct impact on the sound of the instrument… That having been said; the choice of tonewoods does have an impact on the sound:

Tonewoods

Alder (Alnus rubra)

Location: North America

Alder has a full, rich sound with a fat low end and nicely cutting midrange as well as good overall warmth and sustain. It has a bit less bite and high end than ash. Alder is the most common body wood used by Fender Musical Instruments Corporation, commonly used for Stratocaster bodies.

Australian Blackwood (Acacia melanoxylon)

Other names: Black Acacia
Location: A fast growing evergreen with a native range in Eastern Australia. It can age to 50 years and reach heights of 130 feet in the cooler rainforest climates of Tasmania. It can also tolerate poor soil and water conditions.

In its native range, Australian Blackwood is widely exploited as timber. The older, figured logs are now harder to find and consequently rising in cost. New forests are being planted to help assure a steady supply in the future. It has been viewed as an invasive species: It can invade local habits and force out native species. It has been declared a noxious weed species in South Africa. It was also recently listed by the California Invasive Plant Council (Cal-IPC) as an invasive weed,

The heartwood is golden-brown taking on a glow when finished. It can display fiddleback as well as wide color variations. Australian Blackwood has a Specific Gravity around 0.6.

Basswood (Tilia Americana and varieties)

Location: North America and Asia

The principal wood used on most Japanese made instruments since it is a readily available Asian tonewood, although pressure from customers pushed Japanese builders toward ash after 2004. It is a very light wood that is easily worked but has little strength or character. Its tonal response is very similar to alder.

Brazilian Rosewood (Dalbergia nigra)

Location: Rainforests of Brazil

Brazilian rosewood is endangered and on the CITES convention list. It grows independently in the rain forests of Brazil, and can be spread apart by miles between individual trees. To cut and transport a single tree requires destruction of large areas of the rainforest. It is not legal to import Brazilian Rosewood without proper CITES documentation. If you buy a guitar built of Brazilian Rosewood after 1992, be sure to have the CITES documentation for the instrument or you will not be able to sell it over our borders nor take it out of the country.

Sometimes called ‘Jacaranda’, it ranges in color from deep red to violet, with black streaks known as spiderwebbing. There are occasional dramatic streaks of light colored sapwood. The wood smells like roses when freshly cut – hence the name. It has a bell-like tap tone and is extremely sonically reflective. It is believed to produce full, rich bass and brilliant trebles. It was the traditional wood of choice for backs and sides of guitars. Rosewood is inherently dense and, therefore, heavy. It is dense enough that it is often used for bridges and fretboards.

Though much harder to get, the use of Brazilian Rosewood is still very much in demand which translates to high prices. As a consequence some luthiers have resorted to harvesting stump wood. Though the graining on these slab-cut sets may be dramatic, the stability and tone don’t generally match the high price. Sets of Brazilian Rosewood are now common with filled worm holes and other imperfections that would not have been traditionally acceptable.

The Martin guitar company stopped using Brazilian Rosewood back and sides in favor of Indian Rosewood in 1969. Several Martin guitars made in 1970 from Brazilian rosewood have been documented and are widely believed to be guitars started in 1969 but finished the following year.

Bubinga (Guibourtia demeusei and Guibourtia tessmannii)

Other Names: African Rosewood, Essingang, Buvenga, Akume, Bingbinga, Essingang, Kevazingo, Ovang, Waka
Location: The growth range of the species is in the Cameroon’s, Gabon and the Ivory Coast. The species is also in Zaire.

The trees are large, reaching heights of more than 100 feet (30 m) and trunk calipers of 36 inches (90 cm). Trunks are usually well formed and can be 30 to 60 feet (9 to 18 m) long.

The population of the species within its natural habitat has not been officially assessed. Some material is reported to be available from environmentally responsible or sustainably managed sources. The International Tropical Timber Organization (ITTO) reports that the species is a regular source of timber for export. Bubinga is available in lumber form on the US market. Imported logs can weigh as much as 10 tons. The timber is dimensionally stable if slowly dried.

Properties:

Weight:	55-65 lbs/cu.ft.
Density (air-dry):	58 lbs/cu.ft.
Specific Gravity:	0.88
Hardness	65 lbs
Radial Shrinkage:	5%
Tangential Shrink:	9%

Cherry (Prunus serotina)

Location: North America

The weight and density of cherry approaches that of maple. Cherry produces a rich midrange and excellent balance without favoring the bass or treble frequencies. It is rich and red in color that darkens with age and can be found in very dramatic figure. This wood is readily available.

Cocobolo (Dalbergia retusa)

Other Names: Nicaraguan rosewood, Granadillo, Caviuna, Jacarandaholz, Palisander, Palissandro, Palisandre, Nambar rosewood, Pau preto, Urauna, Palo negro, Funera, Cocobolo prieto
Location: From Mexico south through Central America.

The sizes of the trees are small to medium. Mature tree heights are 45 to 60 feet (13 to 18 m). The trunks that are usually of poorly formed reaching diameters of about 20 to 24 inches (50 to 60 cm). Harder and heavier than many rosewoods, Cocobolo can be waxy and difficult to glue. It is stable after seasoning due to its oil content, which acts as a barrier to water absorption. Sawdust has been associated (in allergic individuals) with skin irritation similar to that caused by poison ivy.

Cocobolo is reported to be found in limited quantities in the Pacific regions of Central America: from Panama to Southwestern Mexico. It usually grows in the drier uplands. In theory, this species is relatively plentiful and secure in most areas of its range, including Mexico, Nicaragua, and Panama. It is officially classified as Extinct, Endangered, Rare, or Vulnerable in Costa Rica due to poor harvesting practices and government policy. The actual status in Costa Rica is not known due to inadequate information (Source – World Conservation Monitoring Center – 1992).

Properties:

Weight:	68 lbs/cu.ft.
Specific Gravity:	0.82 (green), 1.00 (dry)
Radial Shrinkage:	3 %
Tangential Shrink:	4 %
Volumetric Shrink:	7 %

Cuban Mahogany (Swietenia mahogani)

Location: Cuba and other Caribbean locations.

Cuban mahogany appears similar to South American mahogany except it is a bit more reddish brown in color. Cuban mahogany is denser than Swietenia macrophylla and the texture is finer. Some woodworkers have compared Cuban mahogany to silk and Honduran mahogany to burlap. You get the idea… The tone is similar to Honduran Mahogany with a better defined treble response.

East Indian Rosewood (Dalbergia latifolia and Dalbergia sissoo)

Location: India.

East Indian rosewood is resinous and generally more stable than most other rosewood species. These woods are plantation grown and the Indian government controls their export. Dalbergia latifolia tends to be harvested from Tea plantations where it is used as a shade tree and Dalbergia sissoo is harvested from controlled forest areas. Both are tonally similar: reflective with a deep warm projecting bass response. Although latifolia and sisso can differ in appearance, East Indian rosewood can be hard to distinguish from Brazilian Rosewood.

Dalbergia latifolia is generally richly grained with dark purples, reds and browns.

Dalbergia sissoo is similar to latifolia except the shades tend more towards red than purple. This can also have crimson streaks.

European Flamed Maple (Acer campestre)

Location: Germany

Curly, flamed, tiger-striped, or “Fiddleback” maple refers to the figuring characteristics in selective cuts of some maple trees. This particular species of European maple is very hard and reflective, producing a strong sound with good projection.

Honduran Mahogany (Swietenia macrophylla)

Location: South America (not just Honduras)

Yellowish brown to reddish brown in color, Genuine or Amazon mahogany is very stable. Mahogany is lighter in weight than rosewood, koa, or maple. In spite of its weight, mahogany yields a strong loud sound with a quick response and an emphasis on a warm, round midrange and bright projecting highs.

Figured Mahogany: This rare and beautiful cut of mahogany occurs in a small percentage of mahogany trees. Figured mahogany shares the same tonal properties of the unfigured mahogany but is harder to find and more difficult to bend. The consequence is higher cost.

Koa (Acacia koa)

Location: Hawaii

Golden red-brown color with light and dark streaks. Koa can also be found with a curly or flamed figure. Some feel that Koa has a bass response slightly less than rosewood and a treble response slightly less than mahogany. The result is a very evenly balanced sound. Our experience is that the sound is very full and rich with a strong projection. Koa has many of the tonal qualities of rosewood but less weight.

Macassar Ebony (Diospyros celebica)

Location: Southeast Asia and the Philippines

A deep and rich sound when compared to East Indian Rosewood. Some characterize Macassar Ebony as similar to Brazilian Rosewood. It is heavy and dense and has similar reflective characteristics to Brazilian. It has a distinctive vertical stripe pattern of variegated dark brown, black and green. A variant: Striped Ebony comes from New Guinea and is responsibly government controlled, and not an endangered species.

Madagascar Rosewood (Dalbergia baroni)

Other Names: African rosewood, Palisander
Location: Madagascar: This species is largely confined to the lowland rainforest plains of eastern Madagascar, often found in marshy areas and near mangroves.

The trees of the many and various species are generally too small to yield 2-piece quarter sawn backs. Smaller pieces are sometimes resawn to create 4-piece backs. With enough spider webbing, color variation and careful joining, it’s difficult to identify if the back is 2 or 4-pieces. The wood is similar to Brazilian in stability and about the density of Cocobolo.

Separated from the African continent for millions of years, the island of Madagascar has evolved an wide array of unique plant and animal species. 80% of the plant and animal species aren’t found anywhere else on Earth. Although Madagascar was once covered in forests, over 90% have already been harvested, removing the habitat for rosewood and other species. Intense pressure on the remaining forests for timber and agriculture has threatened many of these species to the point of extinction.

Recently the Malagasy government increased the number of its protected areas from 2 million to roughly 6 million hectors. After a two-year commercial logging ban was lifted in 2006, there is significant international pressure to introduce improved land management practices for the commercial forestry sector.

Madagascar rosewood, like all rosewoods is heavy, hard, and oily.

Morado (Machaerium scleroxylon)

Location: Bolivia

Also known as Bolivian or Santos rosewood or palisander; the color of morado ranges from light violet brown to reddish brown with some olive and black streaks. It has a finer texture than most rosewoods, morado is visually close to East Indian Rosewood, and has a similar tonal response.

Myrtlewood (Umbellularia californica)

Location: North America

The tonal properties are somewhere between rosewood and maple – as strange as that sounds. It has the powerful voice of rosewood with the clarity, brightness and balance of maple. Myrtlewood can be found in the coastal mountain regions of northern California and southern Oregon. The coloration varies from straight grained white to yellow-green with flame. This can be found in very dramatic figure.

Ovangkol (Guibourtia ehie)

Other Names: Amazoue, Amazakoue, Anokye, Ehie, and Hyeduanini.
Location: Grows in tropical West Africa, primarily the Ivory Coast and Ghana.

Straight to interlocked grain with moderately coarse texture. Yellow brown to chocolate brown heartwood with grayish-black stripes.

Physical Properties: Heavy and moderately hard with high stiffness, strength and shock resistance. Moderate decay resistance and dimensional stability in service. Steam-bends poorly. Works fairly easily with hand or machine tools but saws slowly. Silica content has moderate blunting effect. Reduced cutting angle is recommended during planing to prevent tear-out. Glues easily, stains and polishes satisfactorily, and can be brought to an excellent finish.

Poplar (Populus Liriodendron tulipifera)

Location: America

A lighter and softer hardwood, nicely resonant with a meaty tone. This wood is being used by many electric guitar manufacturers as a substitute for alder.

Walnut (Juglans nigra)

Location: North America

A dense, heavy wood that has the bright tone of mahogany when played lightly and the power of rosewood when you play hard. If properly braced; a walnut guitar can have warmth and tonal depth. This is a dark brown wood that can be highly figured.

Western Hard Rock Maple (Acer campestre)

Location: North America

Similar to European maple but a different figure to the wood. “Birdseye” maple, for example, is often Canadian. Some identify the difference between European and Western Maple by small streaks of minerals found only in European maples.

White Ash (Fraxinus Americana)

Location: North America

A bright and loud tone, but with a warm bass and good sustain. It can be more aggressive sounding than alder. Ash is considered as the traditional Fender Telecaster body wood. Ash is not often used for acoustic instruments.

Ziricote (Cordia dodecandra)

Other Names: Canalete, Freijo, Laurel, Peterebi, Siricote
Location: Several species in the Gerascanthus group of the genus Cordia are reported in Northern Florida, the West Indies, Central America, Brazil and Argentina. Species from Mexico grow at altitudes of up to 1,640 feet (500 m) in tropical dry regions with average precipitation of about 40 inches (1000 mm).

Trees in the Gerascanthus group are described as small to large, and may attain a height of about 100 feet (30 m) at maturity. The timber is naturally resistant to decay by fungi and other wood-eating organisms. It is harder than Hard maple or Teak and very resistant to denting. The species has very high density.

Ziricote is considered to be Not Threatened within most of its geographical range. It is, however, classified as Vulnerable in Mexico (Source – World Conservation Monitoring Center-1992). Some material is reported to be available from environmentally responsible or sustainably managed sources.

Properties:

Density (air-dry):	56 lbs/cu.ft.
Specific Gravity:	0.74

Grading Top-Wood for Musical Instruments

There is no substitution for experience. Once you have handled many peices of tonewood and experienced how they evolve into instruments, you begin to develop a ‘feel’ for how they will ‘sound’. We know of no scientific methods that have a predictable outcome. Measurements will (at least) help the selection of pieces that meet the physical and structural requirements for a musical instrument. The following focuses on the top – the single largest contributer to the final sound.

Visual Inspection

The most commonly seen grading scale for tonewoods is A, AA, AAA, and AAAA (or master grade).

The scale is subjective but useful for the retail of tonewoods. Ironically, when a set of top pieces are uniform, tight grained and beautiful, these are also the atributes of a good sounding top. Like everything else in life, there are many exceptions…

Grade A No knots, swirls or holes and fairly straight grained. There may have uneven color, streaks and uneven grain lines (also called compression). It will probably not be perfectly quartersawn or the piece will be well quartered only for part of its width. Runout is likely. There will be little or no medulary rays – cross-grain figure.
Grade AA is somewhere between A and AAA grade – see below.
Grade AAA has an even overall color with uniform and tight grain lines, evenly quartersawn along the full width of the board and with little or no runout. Grain lines should be tighter than 12 lines per inch. There may be good cross-grain figure, also known as silking or bearclaw.
Grade AAAA (Mastergrade) has uniform color and pronounced cross-grain figuring in addition to being evenly quartersawn with no visible runout and very uniform grain.
Grade AAAAA – Used by some builders to indicate that their wood is better than anyone elses.

Physical Measurements

A feel for the stiffness along the grain and across the grain is what is used by luthiers to determine the size and thickness of a top set for a particular instrument. This Art is learned by experience: the training passed from Luthier to apprentice. The size, thickness and proportion of the top wood combined with the bracing placement and mass determines the responsiveness of the top to the strings. The combination has to be strong enough to structurally survive but light and responsive enough to become a wonderful instrument.

Ther are some effective ways to measure the strength of tonewoods.

In general, the range of thickness of guitar tops is between 0.130″ – 0.095″. The stiffer the board, the thinner it can be and still be structurally OK. The same is true for bracing. In general, braces range in size to a maximum of 5/16″ wide and 3/4″ tall. A thinner soundboard and smaller lighter bracing means less mass. Less mass implies a more responsive and louder instrument.

Standards

The stiffness of a wood beam is measured by how far the beam deflects under a specific applied pressure (MOE).

P = the amount of pressure applied
l = the length between supports
w = the width of the wood sample
t = the thickness of the wood sample
d = the distance the sample deflecteded when pressure was applied

MOE Values of some Tonewood

Species	MOE(x10^6 in/lb^2)	Weight(lb/ft^3)	Top thickness
redwood	1.34	28
Western red cedar	1.11	23	.130″
yellow cedar	1.42	31
englemann spruce	1.30	23
white spruce	1.43	28
red spruce	1.61	28	.110″
sitka spruce	1.57	28
Indian rosewood	1.78	53
African mahogany	1.31	32
ebony	1.43	45
Honduras mahogany	1.42	30
Brazilian rosewood	1.88	47
bigleaf maple	1.45	34
black walnut	1.68	38

NOTES:

“Top Thickness” is intended to be a safe minimum value.
Both red and white spruce are sometimes called Adirondack, note the difference in MOE properties.

The way it all sounds

Structural analysis can help in wood selection, thickness and bracing but it is not a predictor of sound quality. Each Luthier has their own approach to tone and every one that we’ve encountered is in some way unique. This makes sense as the materials are natural and there are no two sets of wood that are identical in the same way that there are no two instruments that sound or feel the same.

Glossary of Terms

Quartersawn

Limber cut perpendicular to the growth rings. Also known as: quartered.

Runout

Wood split with a wedge divides along the weakest part of the wood. When wood is cut by a blade, the wood fibers are torn along the path of the blade. Wood split rather than cut is stronger and therefore preferred for tonewood applications. In wood that has been split, the fibers run uniformly through the piece. In wood cut by a sawblade, the fibers are cut by the blade and do not run continuously through. You can see runout when a bookmatched topwood reflects light diferently from each side of the center joint. In the final analysis, a top with runout is less visually desirable and not as stiff as a top without runout.

Tonewood

A sutable wood for musical instruments.

Compression

Description of the annular ring line spacing varying from tight to wider apart. This was likely caused by a series of warmer winters where the tree has a longer growing season – then shorter colder seasons.

Annular lines

These are also known as growth rings or grain. Annular rings are the lines in wood that correspond to one year of growth. Tight annular rings occur in trees that grow slowly.

Acknowledgemnts

Paul Hostetter, Luthier – numerous web articles
A Guide to Useful Woods of the World by J.H.Flynn & C.D.Holder

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