Posted on July 21, 2026July 21, 2026 by Dale Phillips A Better Approximation to the Rule of 18 A Better Approximation to the Rule of 18 by Mark French Originally published in American Lutherie #132, 2017 Historically, luthiers often used the Rule of 18 to lay out fretboards for guitars and other fretted instruments. (See “Classic Guitar Intonation” by Greg Byers, AL#47; Big Red Book of American Lutherie Volume Four.) While builders seldom now use the number 18 as the coefficient for calculating fret positions, the name is still used as a shorthand way of identifying the method. While 18 is a very convenient whole number, it is far enough from the exact value of 17.81715 that noticeable errors can accumulate. Still, it is often convenient to use a simple approximation for a long decimal number — many of us have used 22/7 as an approximation to π and 355/113 is even better. With this in mind, you can replace the number 18 with 285/16 and lay out frets very accurately. Let’s see where these numbers come from and why the approximation works. Become A Member to Continue Reading This Article This article is part of the Articles Online featured on our website for Guild members. To view this and other web articles, join the Guild of American Luthiers. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
Posted on July 8, 2026July 8, 2026 by Dale Phillips Measuring Resonant Frequencies of an Acoustic Guitar Measuring Resonant Frequencies of an Acoustic Guitar by Mark French Originally published in American Lutherie #143, 2021 Many luthiers track resonant frequencies of their acoustic guitars, often with the goal of meeting some target values. It’s common for the first two resonant frequencies of a full-sized acoustic guitar to be near 100Hz and 200Hz respectively. Some builders use detailed frequency measurements during the build process. For example, Greg Byers described his methods in his 2017 GAL Convention workshop (AL#134). Another good discussion is in Volume 1 of Contemporary Acoustic Guitar Design and Build by Trevor Gore and Gerard Gilet. Resonant frequencies are a function of the ratio of stiffness over mass. Specifically, frequency is proportional to √(stiffness/mass). This simple relationship is harder to apply at higher modes, but it describes the effect of the structure on the lowest modes well enough for us. In practice, it’s easier to reduce resonant frequencies than to increase them. Selectively thinning parts of the top or shaving braces reduces stiffness more than mass, and so tends to reduce resonant frequencies. It’s very uncommon for luthiers to add anything, either mass or stiffness, to their guitars in order to modify dynamic response, though it is certainly a valid thing to do. Trevor Gore is the only one who comes to mind, though there may be others I’ve not heard of. Become A Member to Continue Reading This Article This article is part of the Articles Online featured on our website for Guild members. To view this and other web articles, join the Guild of American Luthiers. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
Posted on June 25, 2026June 25, 2026 by Dale Phillips Beyond the Rule of 18: Intonation For the 21st Century Beyond the Rule of 18: Intonation For the 21st Century by Gary Magliari and Don MacRostie from their 2011 GAL Convention lecture Originally published in American Lutherie #116, 2013 Don MacRostie: I wear a couple of hats. I do product development with Stewart-MacDonald and build Red Diamond mandolins. This is Gary Magliari, the creator of the intonation system we are going to discuss today. We started working on this about five years ago after Gary showed it to me at the Newport Guitar Festival. His method really seems like a benefit to me, and I think it’s time to make everybody aware of what he’s done. I believe there are a lot of little things I can do as a builder to make a good or great, or whatever you want to call it, instrument. Things like using glues and woods that have better acoustic properties, tuning those woods, and applying finishes that improve the output create a better instrument. These are little things and if you leave one out, it can still be a good instrument. Become A Member to Continue Reading This Article This article is part of the Articles Online featured on our website for Guild members. To view this and other web articles, join the Guild of American Luthiers. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
Posted on June 12, 2026June 12, 2026 by Dale Phillips Let’s Catch Up With Graham Caldersmith Let's Catch Up With Graham Caldersmith by Juan Oscar Azaret Originally published in American Lutherie #132, 2017 Hop on a plane in Boston. Fly twenty-seven hours to Sydney, then connect on a prop plane to Port Macquarie on the coast of New South Wales. Rent a car (no, the steering wheel is not on that side, dummy), and drive 60KM southwest. (Stay to the left, the left, the LEFT!) Oops, here comes a traffic circle — drive around clockwise, cars on your right have the right of way, remember to exit left, and stay left. Why is that left wheel always grabbing the shoulder... where the heck is it, anyway? Now out of the city (whew!) and on beautiful Australian farmland — rolling green hills in the mild August winter. Past the logging town of Wauchope and the hamlet of Byabarra. The road narrows to a winding switchback climb up the steep slopes of Bago Bluff, and finally we find ourselves on a high plateau of rich farmland in the town of Comboyne, NSW, population two hundred. Comboyne is the home of luthier Graham Caldersmith and his partner Angela MacPherson (Photo 1). On a recent trip to visit our son in Australia, I took the time to spend a delightful day with Graham and Angela in their enchanting home/workshop/tea house where I learned much about lutherie and acoustics, and enjoyed their wonderful hospitality. Become A Member to Continue Reading This Article This article is part of the Articles Online featured on our website for Guild members. To view this and other web articles, join the Guild of American Luthiers. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
Posted on June 11, 2026June 16, 2026 by Dale Phillips Experiments in Audio Spectroscopy Experiments in Audio Spectroscopy by John C. Moore Originally published in American Lutherie #80, 2004 and Big Red Book of American Lutherie Volume Seven, 2015 R.M. Mottola’s interesting article in American Lutherie #70 (Big Red Book of American Lutherie Volume Six) described the use of audio spectroscopy, with a simple home setup, for the analysis of bass guitars. I had read about a spectrum comparison of a Martin D-28 with a Kaman AA 14-4 in An Introduction to Scientific Guitar Design by Donald Brosnac, and have always been intrigued with the idea of capturing in an objective way the “quality” of the sound of different acoustic guitars. Also, my experience has been that seeing colors of nature is enhanced by having tried to paint them, and tasting beer is enhanced by having brewed some. I felt that analyzing sounds from a guitar would heighten the senses here as well. When I read the Brosnac book, written in 1978, the equipment utilized for the guitar comparison sounded exotic and expensive, and certainly beyond the capability of the casual hobbyist. In Mottola’s article, it was clear that the technology of the PC had brought the potential for such experiments within reach. In fact, I already had hardware that could get me started: a digital camcorder that I could extract wave files from and a Sony Vaio laptop. So I decided to have a go at some audio trials. Become A Member to Continue Reading This Article This article is part of the Articles Online featured on our website for Guild members. To view this and other web articles, join the Guild of American Luthiers. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
