Wood Science: Tom Bedell’s Commitment to Sound Optimization and Sustainability

“Picture a Sitka spruce tree. It’s in a 10,000-year-old forest up in southeast Alaska, and it’s 1486,” Tom Bedell begins. “That seedling sprouts from a pine cone way down at the bottom of a 300-foot-high canopy. There are hungry deer, bunnies, other root systems trying to steal water—it has a one in a thousand chance of growing into a big tree. By 1490, it’s a few inches tall; in 1500, it’s 20 inches. That little tree fights its way up through the canopy, and in 200 years, maybe 300, it breaks into the top, where the sun is shining. Now think of the weight,” Bedell says, making a point about how wood varies, even in the same tree. “The bottom is supporting all the weight, the core is hundreds of years old, and the outside might be 50. The woods in the middle, at the edge, on the bottom, and on top have very little in common.”

Bedell’s passionate commitment to understanding variations in the trees that become guitars—and his guidance of those nuances to consistently reach specific musical conclusions, a process he calls “sound optimization”—are the pillars of his design philosophy at Bedell Guitars and at Breedlove, the two Bend, Oregon–based companies he runs. His reverence for the forest itself goes deep, too: Bedell uses only use dead, salvaged Sitka spruce and koa trees; his myrtle is from Oregon; his ebony and mahogany are harvested by collectives in the Congo and Guatemala; and, because dead Adirondack spruces are rotten from the inside, he works with a company that “goes in about 10 years before an Adirondack would die” to individually harvest them, with the least amount of impact.

If you guessed that Bedell is an unabashed tree-loving hippie, your assumption would be correct—but incomplete. By the time he was 18, Iowa-born Bedell had already been a guitar teacher, importer, and retail store owner; he sold Bedell Guitars in 1968 and went on to earn a degree in Chinese Studies at Stanford. Thirty years later, he and his wife, Molly, bought Great Divide, a store in Aspen, Colorado, renamed it Two Old Hippies, introduced the short-lived import Great Divide guitar line, and resuscitated Bedell Guitars. Bedell bought Breedlove in 2010, and these days, he obsesses about wood, acoustics, and tone between trips to sustainable harvesting sites.

What inspired you to look deeper into wood variability?

When I bought Breedlove and restarted Bedell, I figured there had to be technology that would help us understand how Mother Nature’s wood creates music. It wasn’t simply about carving it to 0.125 inches, gluing it to a back or to a side, and creating a box—it had to be more interesting than that. When I talked to our craftsmen, it became clear that every piece of wood is unique.

What kind of research did you do?

I went far and wide to understand how a guitar top vibrates and what it does to actually push sound. I read article after article after article. We sent an engineer to Cardiff University in Wales, where they’ve done lots of research on classical instruments and how they produce sound. And then I met a custom builder who had been doing a lot of experimentation on exactly what I had been looking for—he taught us a lot about what happens between the top of a guitar and the back of the guitar, in terms of how it generates sound.

What surprised you?

We had been carving every top to 0.125 inches thick, regardless of the wood we were using, but there’s a huge variation in density and frequency response from one wood to another. The mass per square inch is completely different, and even in the same tree, there’s a 30 percent variance in the wood density and frequency response. And looks have nothing to do with density and frequency response, or deflection: a top we might grade 1A because of some visual variances might create a far more beautiful sound than a 5A with no blemishes.

How did that change what you do?

We began analyzing and grading tops based on whether they were going to be stiffer—better for heavy strumming—or softer, with more deflection, which would probably create a better fingerstyle instrument. On a big-body guitar, you’ve got a lot more area; less deflection in that big top will still move a little more than it would on a small-body guitar, so you need to change the characteristics of the top based on whether it’s a big body, a small body, or something in-between. We learned that guitar tops move in two directions: When you activate the strings, it releases the pressure, pushes air into the body, reengages the string tension, and then lifts up and pushes air into the room.

What about the back?

The back of the guitar needs to be substantially higher in hertz than the top. As you add material, stiffness, or weight, the frequency goes up, and as you remove material or reduce stiffness, the frequency goes down. So, if you want to lower the frequency or create more deflection in a top, you take material off; if you want to raise the frequency to get more separation between the back and the top, you want more material in the back.

What questions do you ask when you’re building a custom guitar?

How is the person going to play this guitar? What body type (and body size) do they want? How do they play? Are they going to pick or strum?

We direct the top to deliver a particular sound by how thin we make it. We look at the characteristics of the top’s tonewood: Is it naturally stiff—in which case we might need to take off more material—or is it more flexible, in which case we might take off less material? Are they going to want a wall of music with lots of overtones, crisp and clear individual notes, or somewhere in between? That will tell us the hertz separation we want from the back to the top.

You’re really deciding how you want the guitar to sound before you build it.

Right at the very beginning, we decide what our target behavior is going to be. That tells us what hertz we want to tune that top and back to.

What accounts for the variety of tones and tonewoods?

There’s something about the grain structure of each kind of wood; each has a slightly different nuance, and every wood reflects tones with slightly different efficiency. We don’t understand how Mother Nature does that. If I make a rosewood back and a mahogany back after taking into account their density and frequency, they may be exactly the same, but I’m going to get more mid tones out of the mahogany and more bass from the rosewood. And I can’t tell you why.

What inspired you to get serious about sustainable wood sourcing?

Every tree is in a unique circumstance in its forest neighborhood: It’s surrounded by a variable wildlife, plant life, and animal life; it has variable rain, drought—each tree grows as a unique thing in a forest neighborhood. There’s something very special about that. When that tree dies, or if it’s in its old age, we are careful to harvest it in a way that affects the neighborhood as little as possible.

Do you focus on creating instruments specific to players’ needs, or building instruments that do specific things?

Both. If you come to our shop to get a custom instrument, we’ll watch how you hold a guitar, listen to you play, notice which guitars you like and which ones you don’t, and then design a guitar for you.

What about non-custom instruments?

Our goal is to hit the same fundamental frequency on each model. Each guitar should respond the same: If you play one at your friend’s house or at the store, and then you buy one and we ship it to you, all three should sound and play the same.

That’s aiming high!

As consumers, we’ve been trained to understand that most builders don’t address how wood varies from guitar to guitar; that’s why a consumer finds a guitar they like, they say, “I want that guitar. Don’t get me another one—I want that one.” The difference is that we can say to you, “That one’s already sold, but we can ship you one exactly like it.”

Walk me through the build process.

We start by selecting pieces of wood, deciding what our targets are, and then shaping each one to the target density, frequency, and deflection we want for the top—and to the target density, frequency, and weight we want for the back. After we put bracing on the top and the back, we head to our hand-voicing station, where we use an FFT (Fast Fourier Transform) spectrum analyzer that tells us the top’s frequency; if we need to, we’ll scrape wood off the braces until we bring that down to our target frequency. Then we go all around the top and tap it to make sure that the whole top is vibrating at that target frequency. If it’s not, we’ll carve material off the tone bars until the entire top is where we want it to be. Depending on the body shape and tone quality we want, we tune the back, too. If we want the back to be even higher than the top, for example, we carve the bracing across that back to bring it to our target separation.

After that, we finish the guitar, put the body together, go with the finish, decorate it, put the binding on, string it up, assemble the neck, and put on the frets, tuners, and bridge. Once we get it all set up, lined up, and dialed in, we have a finished guitar.

The guitar retains the resonant frequency all the way through the process?

No. Since we tuned it in the hand-voicing station, we’ve added the weight of the bridge, the finish, and the fretboard, and we’ve probably stuck some electronics in it—we’ve added a lot of variability. At the last stop, someone taps the guitar on the top, reading it through the FFT analyzer, and if we haven’t reached the fundamental resonance for that particular guitar, we loosen the strings, go in through the soundhole, and carve additional material off the brace until we reach the fundamental we’ve set for that instrument.

Don’t the player and the space have a role in the guitar’s sound, too?

The room is part of your guitar sound; the top of your guitar is pushing air into the room, the inside of the guitar top is pushing air against the back of the guitar, and the two of them together are creating the sound that you’re producing. About 80 percent of the energy that creates the sound is coming from that guitar top, no question. It’s moving both ways—it’s moving the air against the back, and it’s moving the air into the room. When you snuggle up to your guitar when you’re playing it, and you have your hands resting on that top, you’re affecting the amount of music that the room is helping you create.

Consistency is great, but the wide variation between instruments can be fun, too.

Because then you can say, “Mine is really special.” Every guitar is different. Someone brought in a ’30s or ’40s Martin dreadnought the other day, one of the really good ones, and he was so proud of it. It made him happy, and it sounded terrific, so it made me happy, too!

An abridged version of this interview appeared in the December 2018 issue of Acoustic Guitar magazine.