From the October 2016 issue of Acoustic Guitar | BY ADAM PERLMUTTER


Glossary of Terms

Fundamental vs. Overtones  A fundamental tone is the initial sound heard when you pick or pluck a note (and which decays at varying rates depending on the sustain); the overtones are complex harmonic layers that can make the note swell after the fundamental is initiated. “The fundamental is the root frequency as a tone generator would make it,” luthier Bruce Sexauer wrote on the Acoustic Guitar Forum. “So the fundamental of A 440 is exactly 440 cycles per second. Overtones [are] the harmonic sequence above the fundamental. The first is the harmonic fifth, then the octave, and then things get complicated. The higher [you] go up the series, the looser the direct relationship with the fundamental.”

Harmonic Content   A piece of wood is capable of producing a fundamental tone and an array of harmonics (which include overtones). Tapping a piece of wood reveals, not only the velocity of sound,
but also harmonic content, clarity of tone, and high-, low-, and mid-bias.

Sustain  Natural reverberation that results in a lasting, ringing tone.

Torrefaction  A process in which the soundboard is thermally cured in an
oxygen-free environment to alter the
cellular structure of the wood in a manner that replicates an aged tone.

Velocity of Sound The speed at which a material transmits received energy. Lively materials—those with a high velocity of sound, or low internal damping—best facilitate the transmission of vibrational energy (sound waves oscillating from the bridge). To test velocity of sound, a luthier will hold a piece of wood at a nodal point and tap it to listen for the response.

There was a time when guitars sported a limited range of tonewoods, when steel-string players paid little mind to their distinctions, other than financial considerations. A guitarist flush with cash might opt for an instrument with a spruce top and rosewood back and sides, while one with lesser means would go for plain mahogany back and sides, and a player with even less cash, or a beginner, might choose an unadorned all-mahogany instrument.

But as the steel-string guitar has evolved, luthiers and players alike have become more attuned to the sonic characteristics inherent to different tonewoods. On the other hand, supplies of premium tonewoods have been diminishing due to increased demand, land development, and poor forest management. That’s led to the use of sustainable woods for more than a decade, Martin Guitar, for example, has offered models built with woods certified by the Forest Stewardship Council (FSC). In response to this unfortunate, but predictable, situation, but partly out of pure experimentation, builders also have sought alternative tonewoods, or, in some instances, they’ve used such synthetics as carbon fiber. The San Francisco-based Blackbird Guitars, for example, has even created a highly resonant, proprietary plant-based synthetic called Ekoa.

Indeed, tonewood options are expansive. Major acoustic guitar companies, like Taylor Guitars and Martin & Co., now offer dozens of standard tonewood choices—solid woods, laminates, and synthetics—while a major supplier like Luthiers Mercantile International carries scores of options, including increasingly popular thermally cured soundboards.

There are many variables to consider.

“Differences between woods can be as mysterious and complex as differences between people,” Maine luthier and AG contributor Dana Bourgeois has written in this magazine. “Even within a species, no two pieces of wood are exactly alike. Environmental conditions, genetics, the age of the tree, annular growth patterns, grain orientation, curing conditions, and so on all have an effect on the tonal properties in a piece of wood. In addition, tonewoods respond differently in the hands of different makers. They can also take on different characteristics when used in different models of guitars—even those built by the same maker.

“Whether a particular wood sounds good or bad depends partially upon who’s doing the listening. So any attempt to sort out distinctions between tonewoods can only be offered from a relatively subjective point of view.”

This presents an interesting conundrum for the acoustic guitarist—what are the perfect woods for your sound? If you find yourself in this position, this tonewood primer should help steer you in the right direction to realize your musical vision. Of course, you’ll want to play, and listen to, as many different options as possible before choosing your dream guitar.

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The All-Important Soundboard

The top or soundboard, as the name suggests, bears more influence on the way a guitar sounds than any other component, though the back also is a key component. “In general terms, the top seems to affect the guitar’s responsiveness, the quickness of its attack, its sustain, some of its overtone coloration, and the strength and quality of each note’s fundamental tone,” Bourgeois notes. “Most luthiers, but not all, believe that the wood chosen for the top is the single overriding variable that determines the quality of tone of a finsihed instrument.”

Spruce is the most common tonewood for the steel-string soundboard (there are a half dozen species in the Northern Hemisphere). Sitka, which grows in coastal rainforests in the Pacific Northwest, is used most often, though such manufacturers as Taylor Guitars have introduced Lutz spruce, a hybrid of Sitka and white spruce that reportedly has some of same tonal characteristics of Adirondack spruce.

Sitka Spruce

Arguably the most common tonewood, Sitka is a well-rounded tonewood, one suited for many styles of playing. It’s known for its tight grain pattern and its high stiffness and relative lightness, translating to a broad dynamic range that stands up well when strummed heartily. At the same time, it’s also quite responsive to fingerpicking, though a light touch may result in a thin sound. Sitka tends to have stronger fundamentals than overtones, and this means that it can sound not quite as robust when played with the lightest touch. “Sitka is the most consistently available, good-quality spruce there is, and that’s why we use it as stock on the majority of our guitars,” says Dick Boak, director of the museum and archives at Martin & Co.

Examples: Taylor 914; Breedlove Pursuit; Martin GPCPA5

Engelmann Spruce

Engelmann spruce, which also grows in western North America, is a common alternative to Sitka. Because it is in lesser supply than Sitka, Engelmann often costs more. It’s a lighter and less stiff variety than Sitka, and it has stronger overtones and weaker fundamentals. An Engelmann top typically has less headroom than one made from Sitka, and its sound can suffer a little when played loudly. “Engelmann is a good choice for players who want a more complex sound when playing softly,” says Bourgeois, adding that European spruce shares characteristics with Engelmann, but has more headroom, making it ideal for players with a stronger attack.

Examples: Yamaha CG122MS Classical; Collings OM2HE

Lutz Spruce

When Taylor Guitar redesigned its popular 700 series this summer, the company turned to Lutz spruce, a natural hybrid of Sitka and white spruce that provides a higher volume ceiling. Taylor is no stranger to Lutz; the world’s largest acoustic-guitar manufacturer introduced this tonewood into its lineup in January with the revoiced 500 series. According to Pacific Rim Tonewoods, it grows naturally in a relatively small area in Central British Columbia and the Alaskan panhandle. The supplier hails Lutz spruce for its “hybrid vigor.”

Examples: Taylor 712ce; Halcyon NL-00

Adirondack Spruce

Adirondack, or Eastern red spruce, named after its ruddy coloring, grows in the Adirondack Mountains and in the cool forests of the Northeast. It is the king of spruces. Prior to World War II, it was the soundboard tonewood of choice for Martin and other makers. But over-harvesting of this wood led to its being all but phased out for use in guitars in the years after the war. For the most part, Adirondack spruce can be found on select high-end instruments. It’s a relatively heavy and stiff wood, having strong fundamentals, but a greater overtone content than Sitka, and it tends to be the loudest and liveliest of spruces as well.

“Adirondack can be extremely wide-grained—as few as four grains per inch—and not as pretty as other spruces,” Boak says. “But it has the uncanny ability to add complexity
to the tone.”

A spruce soundboard on a new guitar can have a bit of an edge to its tone, and many players like the way it starts to open up with playing time—something to take into account when auditioning any brand new spruce-topped instrument. Al Petteway, the master fingerstylist based in the Asheville, North Carolina area, says, “I’m not sure how much it has to do with the top aging and how much it has to do with the vibrations loosening it up. I’ve played vintage guitars that still sounded stiff because they were left in the case and never played and I’ve played guitars that are less than a year old that sounded awesome.”

Examples: Gibson Hummingbird Vintage;
Martin CEO-7; Blueridge BR-163A
Top Craftsman Series

Western Red Cedar

Though it’s used more commonly for the soundboards of classical guitars, red cedar, growing in western North America, can make a great steel-string soundboard. This wood tends to have a honeyed color and is known for its sonically analogous dark and lush tone, and also for being generally less bass-y and projective than spruce. For these reasons, a cedar-topped guitar is a good choice for a fingerpicker (it’s common on classical nylon-string guitars), but not necessarily a strummer with a heavy attack.

Examples: Taylor 714; Cordoba C9 Luthier Series; Seagull Guitars Coastline S12

Mahogany & Koa

Hardwoods like koa, native to Hawaii, and mahogany, a Central and South American species, are sometimes used for soundboards, usually with backs and sides of the same material. These woods are low in overtones and sound very direct, with impressive mids. The combination of a mahogany soundboard with a back and sides of the same woods is midrange-rich and punchy and works especially well for country-blues fingerpicking.

Examples: Martin D-15M; Breedlove Pursuit Concert Koa

Maple

Maple is occasionally used for soundboards, but more often for backs and sides, due to its flatness of sound and for its relative shortness of decay—an attribute that happens to make the wood more resistant to feedback in amplified situations than rosewood or mahogany. Not all builders find maple to be a suitable top material, though. “I wouldn’t typically recommend maple as soundboard tonewood,” says Andy Powers, Taylor Guitars’ master luthier. “One of its singular characteristics is that it’s almost perfectly transparent—it doesn’t sound like anything, which isn’t usually how you want a top to respond.”

Examples: Fender T-Bucket 400 CE;
Rayco Squareneck Resonator

Fretboards & Bridges

Fundamental vs. Overtones 
Players of electric guitars with bolt-on necks have long been hip to the fact that neck and fretboard materials can have a significant bearing on tone. Maple necks can impart a bright, poppy tone that can do much to reinforce the top end of a large-bodied guitar, while mahogany necks help push the overall palette into a warmer, more woody tonal range.

Fretboard materials also exert an influence on overall tone, although they probably act more as icing on the cake than as a layer of the cake itself. Brazilian rosewood fretboards and their denser rainforrest counterparts add sparkle and ring, and Indian rosewood fretboards can help fatten up the midrange. Wenge, a dense, dark-colored African hardwood unrelated to the rosewoods, has tonal properties remarkably similar to those of Brazilian rosewood.

Ebony, the traditional fingerboard material found on violins, classical guitars, and high-end steel strings, has the lowest velocity of sound of all the woods commonly used in lutherie and has definite damping characteristics. This may not be much of a problem for large-bodied guitars made of red spruce or Brazilian rosewood, but it may be something to consider when designing smaller guitars, particularly those using some of the less resonant woods for tops and backs.

Bridge materials, like fretboards, cannot make or break an instrument, but they serve to enhance or edit the tonal contributions of other materials found on the guitar. The woods discussed above­—ebony, Brazilian rosewood, and Indian rosewood—contribute similar tonal qualities when they are used as bridge materials as when they are used for fretboards.

It is important to remember that wood, when considered generically, can be responsible only for certain aspects of the tone of any guitar. Equally important are the design of the guitar, the skill of the maker, and the quality of the individual pieces of wood from which the guitar is made. Species selection can, however, be a determining factor in the creation of a very special guitar or a guitar designed for a specific purpose.

 — Dana Bourgeois
Excerpted from the 1994 Acoustic Guitar article “Tapping Tonewoods.”

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The Back & Sides

Rosewoods

The back and sides contribute far less than the soundboard to a guitar’s sound, but their composition is nonetheless important. Rosewood, which takes the name from its characteristic floral scent, is an ideal tonewood for backs and sides. “Rosewood is dense and heavy compared to other woods—almost so heavy that it sinks in water,” Boak says.  “And it produces extremely warm and resonant tones.”

In no small part due to its use in classic Martin guitars, Brazilian rosewood has long been considered the Holy Grail. Native to southeastern Brazil’s Atlantic Forest, this precious tonewood, also used for centuries in high-end furniture, became difficult to source in dimensions large enough for guitar-making in the last half of the 20th century. Because of this, in 1969, Martin started using Indian rosewood instead of Brazilian.

While Brazilian rosewood has been offered in fancy instruments since then, both by guitar companies and independent luthiers, it has become even trickier to obtain. In 1992, it was added to the Convention on International Trade of Endangered Species treaty, and then, in 2008, to the federal Lacey Act, which made it impossible to import Brazilian rosewood without a labyrinth of permits and paperwork. (Under those U.S. and international statutes, documentation is required to travel with a
Brazilian rosewood guitar.)

Nonetheless, some U.S. guitar makers have Brazilian rosewood that pre-dates the ban and it’s still used on costly reissue and boutique guitars. What makes Brazilian rosewood so appealing is its great beauty—its deep, variegated coloring and its spider-web figuring. But more important are its brilliant overtones, deep resonance, and impressive sustain, its penetrating basses and crystalline trebles. “Brazilian rosewood is so rich and ring-y, and it has such a big range of workability, that no matter how it’s used it yields pleasing musical results,” Bourgeois says.

East Indian rosewood—sometimes referred to just as Indian rosewood—is native to the tropical monsoon forests of southeast India and is much easier to source than its Brazilian counterpart. That’s why it’s used in the vast majority of new rosewood guitars. Indian rosewood is a versatile tonewood, equally good for flatpicking and fingerpicking, with scooped mids, a deep low-end, and bright high end. Its sparkling sound makes it a great substitute for Brazilian rosewood. “Indian rosewood has a lot of the same characteristics of Brazilian rosewood—but just a little less of everything,” Bourgeois says.

Some less common alternatives to Brazilian rosewood, which share some of that prized tonewood’s winning qualities, include Honduran, Guatemalan, and Madagascar rosewood, as well as cocobolo, granadillo, ovangkol, wenge, and ziricote, among others. “Honduran is my personal favorite,” Boak says. “The tree doesn’t grow very large, and it’s hard to find supplies sufficient for a two-piece back. Martin actually used to cut Honduran rosewood logs for Musser, a premier maker of marimbas. The wood rings like nothing else when it’s hit with the right type of mallet, and whenever we use it on a custom guitar, the results are quite extraordinary.”

While rosewoods might sound amazing, a guitar made from this species, with its complex overtones and sustain, can present headaches for a recording engineer. An instrument whose sonic spectrum is cluttered is more difficult to record than one with a comparably direct sound. So, in the studio, mahogany backs and sides can be preferable to rosewood.

Examples: Taylor 416-R; Gibson J-45;
Martin D-16RGT

Mahogany

Honduran mahogany, (also called Honduras mahogany, big-leaf mahogany, or simply mahogany) has a warm and woody sound, high in midrange content, that’s dissimilar to rosewood. It’s characterized by a relative high velocity of sound and strong fundamental content, though it lacks rosewood’s brilliant ringing overtones, making it a good choice for a player who wants a clear, direct sound, and for recording in general. “Mahogany is quite light compared to rosewood, and sonically, with its airy crispness, it’s kind of the opposite of rosewood,” Boak says.

While mahogany is much easier to source than Brazilian rosewood, it’s still an endangered species, due largely to illegal logging. And so guitar makers have sought sustainable alternatives. An inexpensive option like sapele, for instance, which is sometimes called Africa mahogany, behaves a lot like Honduran, but adds a little treble shimmer. Khaya, another mahogany substitute, is also known for its brightness.

Examples: Martin 000-15M;
Guild M-20

Sapele

Comparable to mahogany with consistent, balanced tone, this African tonewood is sometimes seen as the poor-man’s mahogany (Martin sometimes offers it as a substitute on the company’s popular 000-15M model)—it is slightly denser than mahogany and produces a brighter tone. But overall, sapele is known for warm resonance and good projection.

Examples: Martin DRS-1; Taylor ‘Baby Taylor’

Ovankol

This African relative of rosewood shares many of its tonal properties, and it is sometimes known as African rosewood. Its color ranges from yellowish to reddish brown to darker gray with black stripes, resulting in an attractive grain with an attractive flame. It has the same bass and treble as rosewood, but a bit more mid-range.

Examples: Taylor 410

Koa

Falling between rosewood and mahogany is koa—a tonewood Martin first used on guitars in 1917, as a craze for all things Hawaiian swept across America. Koa is native to Hawaii and is used commonly on ukuleles, but less so on guitars. It’s prized for its rich golden coloring, curly figuring, and agreeable sound. “In my estimation koa splits the difference nicely between rosewood and mahogany,” Boak says. “It exhibits some of the warmth of rosewood and some of the breath of mahogany.”

Taylor K24ce Koa ES2 Grand Auditorium; Dean Exotica Koa

Maple

An excellent North American tonewood for back and sides is maple, Eastern hard-rock and Western big-leaf maple being the most commonly used types. A couple of years ago, Taylor Guitars expanded its use of maple on backs and sides, and has undertaken an active maple reforestation program. Maple is celebrated both for its range of figuring patterns—from curly or flamed to quilt to birdesye, which add beauty to an instrument—and for its transparency of sound, which reflects the sound of the top but doesn’t so much color it. Maple can be loud and projective. “I’ve owned three guitars with flamed maple back and sides,” says Petteway. “They were all awesome. I’ve always felt maple is a great-sounding wood. After all, it’s what’s been used on stringed orchestral instruments for centuries.”

Gibson J-200; Taylor 616

Walnut

Historically, walnut hasn’t seen widespread use among guitar makers, but there are notable exceptions, like certain Epiphone archtops from the 1930s. It’s used increasingly in modern guitars, though. Claro walnut can have a striking figuring that lends eye candy to a fine guitar. Walnut behaves similarly to maple, though it has its detractors. “To my ear, walnut has a warm and very dark tone—sometimes too dark. I’m not really fond of walnut, although it sometimes pleasantly surprises me,” Boak says.

Examples: Larrivee L-03 Walnut Acoustic Guitar; Gibson 2016 SJ-100 Walnut Jumbo

Cocobolo

With its spice-like scent and far-ranging coloration (with deep, black grain), this Central American relative of rosewood is known as the “piano of tonewoods,” since it produces a bright, sparkling tone that accentuates the treble. Regarded as one of the world’s finest tropical woods, cocobolo grew increasingly popular after the 1912 opening of the Panama Canal made its transport easier.

Examples: Martin Custom Shop 000-14;
Luna Vista Wolf Grand Auditorium

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Alternative Woods & Synthetics

Tradition casts such a strong spell in the guitar world, especially among high-end instruments, that it is difficult for a “new wood” to gain any sort of status recognition. “Adventurous luthiers do find and use exciting new woods, but rarely are the woods feasible options for manufacturers because, even if they are sustainably harvested and non-threatened, they are scarce, or the trees are rarely large enough for guitar plates, or they require additional care during the building process,” says Chris Herrod, LMI’s sales manager, on alternative tonewoods.

“Frankly,” he says, “the outlook for exotic, especially tropical, wood sources grows more and more bleak every year and we are not seeing a newcomer emerge that will fill in for fading species and heroically save the day. The future, in my opinion, will not rest on new woods defining the value of a guitar so much as a fresh appreciation of tonal nuance and power—along with an increased capacity to communicate effectively about it—and for the artistry and execution of fine woodworking and ornamentation on the guitar.”

With that in mind, the door will be opened for acceptance of four-piece tops and backs, less ornate woods, laminates, and composite materials (Nomex or honeycombed tops, other non-wood materials) and for tempered (“cooked”) and otherwise treated woods—even in high-end, heirloom-quality guitars.

Examples: Rainsong Black Ice Series;
Kevin Michael Touring Carbon Fiber;
Martin 000X1AE; Blackbird El Capitan

Laminates: To Layer or Not to Layer

A layered or laminated tonewood is one in which several thin sheets of wood are glued together to form a material that’s inexpensive and durable to work with. Layered tonewoods sound less complex than their solid-wood counterparts and are generally reserved for budget and import guitars, with the exception of high-quality electric guitars, like those in Gibson’s classic ES (Electric Spanish) series.

The main benefit of buying a guitar with layered tonewoods is that it will have an attractive price—and often visually pleasing outer layers on those woods. And then there’s the green thing: by definition, laminates help guitar makers make the most efficient use of precious materials from the forest.

The least expensive guitars have bodies made entirely from laminated tonewoods, but many good-quality, affordable options pair solid soundboards with layered backs and sides. Given how much more a soundboard impacts a guitar’s sound and performance than do its back and sides, this is a very good compromise.

Examples: Taylor GS Mini;
Martin & Co. LX ‘Little Martin’

Salvaged & Sustainable Old-growth Tonewoods

As supplies of classic tonewoods like spruce, rosewood, and mahogany are being threatened, luthiers and guitar companies look to sustainable alternatives such as salvaged woods. All of the Sitka spruce used in soundboards by Bedell Guitars, for instance, comes from trees that have fallen or are dead in Alaskan forests.

As for harvesting tonewoods sustainably, Taylor Guitars has taken important steps in this direction. For its 600 series, the company uses North American maple, grown in healthy forests with good stewardship, ensuring that it will be available for generations to come. This maple is supplied by Pacific Rim Tonewoods, a company with thoughtful practices when it comes to sourcing and preparing woods for musical instruments. The company also is planting its own maple forests, as well as stands of koa on the Hawaiian islands.

In a more ambitious development, in 2011 Taylor bought an ebony mill in Cameroon, Africa, and is now the world’s biggest legal producer of that wood, used most often for fingerboards and bridges. The ebony market has long been plagued with irresponsible and wasteful forestry, compounded by corruption, and Taylor is working to operate cleanly in a way that ensures ebony’s survival.

Sinker wood—logs that long ago fell to the bottoms of rivers or lakes when being transported for milling purposes—is another source that precludes the harvesting of new tress. Huss & Dalton, for example, has built guitars using old-growth mahogany discovered in the river bottoms of Belize and removed in an environmentally sensitive manner. “If you like wood with a story, then it doesn’t get any better than this material,” writes Mark Dalton. “This is material from the bottom of Belizean rivers. Belize used to be a British colony. The British exported a lot of mahogany from Belize throughout history and during the 19th century they used the rivers of Belize as their main source of transportation. Occasionally the denser mahogany logs would sink! These logs for over 100 years had been lost and forgotten, until now.All the logs were salvaged using environmentally sound practices using small boats and pulleys to remove these logs off the bottom of the rivers. The logs were cut in Belize using local labor. Hence this is a very eco-friendly product. The material was kiln-dried in Belize, but has been re-stickered to give the piles air flow to allow them to air dry even more. Due to the age of these logs, all this material would have been old-growth timber. The color is excellent and the grain is tight. Some of the material is even figured. Plus the material has a very interesting natural edge. The texture has been sculpted by the river and is very pleasing to the eye.”

Slabs of tonewood from an ancient mahogany trunk known iconically as The Tree are among the most coveted tonewoods—even Slash of Guns N’ Roses had a custom acoustic built from The Tree (read about it in the March 2016 issue of AG). But that’s not even the most impressive salvaged tonewood: Earlier this year, Santa Cruz Guitars exhibited at the Winter NAMM Show a one-of-a-kind H13 model fashioned from a set of 8,000-year-old oak boards cut from a trunk found in a Czech sandpit and a fallen 3,000-year-old Sitka spruce tree salvaged from the melting Arctic permafrost. A unique guitar built of woods from the dawn of civilization (featured in the June 2016 issue
of AG).

Guitars Don’t Live By Tonewood Alone

More than just the species of wood will have a big influence on how a guitar sounds. The way it’s cut, for instance, will affect both its workability for a guitar maker and its sonic performance. Quarter-sawn lumber—in which the wood is sawed at a radial angle into four quarters—is optimal for tops, as it lends stiffness. “A quarter-sawn top is stiffer [than a plain-sawn one],” Chris Herrod, sales manager at Luthiers Mercantile International, explains. “Great stiffness gives the wood greater resonance, all other things being equal, and allows the luthier greater leeway to alter the tone and response of the top by changing the thickness.”

It’s also important to remember that a guitar’s design has more influence on its sound than the tonewoods used to build it. Though rosewood, for instance, generally has a stronger bass response than mahogany, a mahogany dreadnought can easily have a more impressive bottom end than, say, a rosewood parlor guitar. A couple of other variables that impact a guitar’s sound are its setup—an instrument with overly low action tends to have an anemic tone even if it’s made from the most optimally resonant tonewoods—and even its scale length. “A long scale length will normally accentuate the trebles, for example,” Herrod says.

Keep in mind, too, that the sonic performance of a particular tonewood depends not only on the wood, but also the build of the instrument. A finely made plywood guitar, for instance, will likely sound superior and be more resonant than a poorly built rosewood guitar—just as the finest guitar made from premium Adirondack spruce and Brazilian rosewood will only sound as good as the guitarist playing it.

AG editor Greg Cahill and Dana Bourgeois contributed to this article.


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This article originally appeared in the October 2016 issue of Acoustic Guitar magazine.

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