Brian Burns Guitars
Luthier made classical and flamenco guitars

Guitar making instruction

My Process
There are three steps in the guitar making process that are really important to get right, in order for the guitar to be a superior instrument.

~Wood Testing---Selecting wood with the best mechanical and acoustical qualities.

~Initial Voicing---Getting the back and soundboard reduced to optimum thickness.

~Final Voicing---Making adjustments to the guitar body that place the main                 resonances at the right pitches (frequencies) for best tone quality.

Wood Testing
for stiffness and density
Wood is a natural material, and it varies---dramatically! When I first began making guitars, back in the early 1960’s, I assumed that “tonewood” suppliers were selling wood that was suitable for building good instruments. They use a variety of grading systems, but it mostly comes down to appearances, as they can't afford to put in the time and effort required to test for all the properties that matter to the guitar maker. So now I depend on my own testing to help me select the best quality woods to use in my guitars.

I do a series of tests on the woods that I use to determine their acoustical and mechanical properties​. These tests allow me to accurately judge the quality of the woods so that I can select the best for a particular guitar. What would be the best choice for a classical guitar would probably not be the best for a flamenco guitar. And, there are a lot of "tonewood" back and soundboard sets that just don't measure up to my standards. Nylon string instruments are particularly sensitive to wood quality, and I'll only use the best that I can find.

There is still a good deal of art to wood selection as there are subtle differences between species that don’t show up in my tests. For soundboards I like European spruce, western red cedar, and coast redwood. For backs and sides I use East Indian rosewood, California cypress, and sometimes other woods like Western Maple and Spanish Cedar.

Here is a link to a downloadable file of the Wood Testing Notes that I give my guitar making students. They have lots of photos.
Wood Testing Notes.pdf

Wood Testing Part 1

Wood Testing
for acoustical quality

I use an acoustical analysis program on my PC called Spectra Plus . In each construction phase, I make the wood vibrate and the computer listens through a microphone to the ways in which it resonates. Spectra Plus displays the  resonances as a graph on my computer screen. The graph shows me the strength of each resonance, and its frequency (pitch). In effect, I get an acoustic "fingerprint" of the part of the guitar, or of the guitar as a whole.

Many thanks to John Pattee for writing this wonderful program! I hope to sell him a guitar after he gets his kids through college...

Wood Testing Part 2
Initial voicing
The “initial voicing” stage is where I thin the soundboard and back to just the right thickness for those parts of the guitar.

I clamp them up on a guitar shaped test apparatus, and make them vibrate by tapping them with a tiny rubber hammer. Spectra Plus then tells me the lowest pitch where they are resonating. As I gradually thin them down, a few thousandths of an inch at a time, the pitch of that lowest resonance goes down too.

My favorite spots in the acoustical spectrum are 75 Hz for sound boards and 65 Hz for backs. Final weights and thicknesses of these critical parts of the guitar vary 20-30%, depending on their density and stiffness!​

Here is a link to a downloadable file of the Initial Voicing Notes that I give my guitar making students. They have lots of photos.

Initial Voicing Notes.pdf

Initial Voicing

Final voicing
In the final voicing stage I look at where the guitar's main resonances are located in the audio spectrum. Traditional Spanish guitars all have the same favorite ways of resonating, and when these resonances are located higher up in the audio spectrum, the guitar is said to be "bright". When its resonances are located lower in the audio spectrum, the guitar's tone  is said to be "dark".
Here is a link to a downloadable file of the Final Voicing Notes that I give my guitar making students. They have lots of photos.

Final Voicing Notes.pdf

Final Voicing Part 1

Final Voicing Part 2