Posted on June 21, 2025September 15, 2025 by Dale Phillips The Helmholtz Resonance The Helmholtz Resonance A Brief and Not-Too-Technical Introduction to the History and Theory of the Lowest Sound-Producing Mode, and Some Practical Considerations for Instrument Designers by R.M. Mottola Originally published in American Lutherie #82, 2005 and Big Red Book of American Lutherie Volume Seven, 2015 Research in physics and acoustics of stringed instruments shows us the mechanism by which sound is produced by those instruments. The plates of the instruments and the air inside vibrate in various patterns, each pattern producing sound in a range around a certain frequency. Each of these patterns can be considered to be a resonator, each with its own characteristics. Some of these resonators exist as modes of vibration of different areas of the plates of an instrument, and some are modes of vibration of the air inside the instrument. One of the air resonators is composed of the mass of air inside the instrument and the mass of air within and around the soundhole. The natural frequency of this resonator is near the lowest note that an instrument can make. It is generally labeled the A0 resonance, the letter A standing for the word “air” and the numeral 0 indicating that this is the first in a series of air resonances. This resonance is also referred to as the so-called Helmholtz resonance. Understanding how this resonance works in stringed instruments is not difficult, particularly given a historical perspective. Complete understanding involves some math, but a practical understanding can be had without it. Therefore, I am putting off presenting the formulae in the main article and have included them in a sidebar. 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 21, 2025September 15, 2025 by Dale Phillips The Helmholtz Formula The Helmholtz Formula by R.M. Mottola Originally published in American Lutherie #82, 2005 and Big Red Book of American Lutherie Volume Seven, 2015 The resonant frequency of a mass spring resonator can be determined by the following formula: 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 7, 2024May 22, 2025 by Dale Phillips Letter: Career Anecdotes Letter: Career Anecdotes by Michael Cone Originally published in American Lutherie #32, 1992 and Big Red Book of American Lutherie Volume Three, 2004 Dear Sirs: I built my first classical guitar in 1968. Since that time I have been fascinated with the quality of sound of the classical guitar, so it was with great interest that I read Alan Carruth’s articles on guitar plate tuning. Early in my career I had a dream, and in the dream I was playing a classical guitar. You know it was a dream because the guitarmaker was actually playing. This guitar did not sound like a guitar, though; it sounded like a complete orchestra. It was at that point I realized what possibilities were inherent in the guitar and dedicated myself to realizing at least some of these possibilities. 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. Members also receive 3 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
Posted on July 1, 2024May 22, 2025 by Dale Phillips Letter: Technical Qualm with Jim Blilie’s Article in AL#100 Letter: Technical qualm with Jim Blilie’s article in AL #100 by Alan Carruth Originally published in American Lutherie #101, 2010 Tim — I really enjoyed AL#100. It’s a nice mix of “technoid,” “art,” and “craft” articles. Lots of good info, but I did see a couple of things I wanted to respond to. First, in Jim Blilie’s article, which was excellent overall, I have a disagreement that rises above the level of minor. He says, on p. 31: “The fact that the relationship between stiffness (Young’s modulus) and density is inherently linear shows that just changing wood species doesn’t affect the stiffness-to-weight ratio very much.” The problem with that is, while the lengthwise Young’s modulus (E) values for both hardwoods and softwoods tend to fall on straight lines, they are different lines, owing to differences in basic structure in the woods. I’ve been measuring the properties of wood samples for several years. I’m enclosing a graph of long grain E vs. density for most of the pieces I’ve measured so far (147 samples), with eyeballed “average” lines drawn in. The softwoods include all of the usual-suspect top woods, as well as white pine and Mediterranean cypress. As you can see, the points fall very close to a straight line toward the left side of the chart. The hardwoods include a lot of lutherie woods (most of the samples are Indian rosewood), and some others, with balsa and blackwood being the end points. As you can see, the scatter of the points is greater, but they do at least suggest a line. One could, of course, draw a single line that took in all of the data points, but at the cost of accepting quite a lot more scatter in the softwood data. Given the relative homogeneity of softwood structure, this seems unwarranted. Besides, the resulting line would not approach the origin at all closely, which would be illogical. As is, the hardwood line is in no way an extension of the softwood line. Balsa, and yew, ’way down on the left, overlap the softwood area, as do a few of the softer hardwoods, such as butternut. Still, compared with the softwoods, hardwoods tend to have higher density for the equivalent E value. Become A Member to Continue Reading This Article This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. If you are already a member, login for access or contact us to setup your account.
Posted on June 30, 2024May 6, 2025 by Dale Phillips Radiation from Lower Guitar Modes Radiation from Lower Guitar Modes by Graham Caldersmith Originally published in American Lutherie #2, 1985 and Big Red Book of American Lutherie, Volume One, 2000 Since 1982 when I attended the Estes Park GAL Convention, and subsequently wrote about “Dissolving the Mysteries”1 (of guitar behavior — perhaps a presumptuous title), as a distant but faithful member of GAL, I have followed the developing discussions in the Quarterly about guitar top and back vibrations, how they are excited by the plucked strings and how they generate sound. At our January 1985 Australian Association of Musical Instrument Makers Convention (featuring strong GAL membership) the geometry of the lower vibrational modes of guitars and their appearance in the guitar frequency response records was keenly debated by practicing guitar makers, amply demonstrating luthiers’ adoption of scientific knowledge as part of their working repertoires. Tom Rossing’s contributions to GALQ2, 3 the thoughtful articles by Paul Wyszkowski4, 5, 6, 7 and the monumental “Kasha Guitar Soundboard”8 by Gila Eban, together with some detailed correspondence to me from Gila on her development of the Kasha soundboard all indicate the integration of guitar physics into guitar evolution. I think such unification of science, art, technology (and good ol’ workbench cunning) is healthy and fosters excellence. 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. Members also receive 3 annual issues of American Lutherie and get discounts on products. For details, visit the membership page. MEMBERS: login for access or contact us to setup your account.
