Posted on June 30, 2024May 14, 2025 by Dale Phillips The “Corker” Guitar: A Sideport Experiment The “Corker” Guitar: A Sideport Experiment by Alan Carruth Originally published in American Lutherie #94, 2008 Over the past few years there has been something of a trend for cutting holes of various sizes and shapes in the sides of guitars. (Editor’s note: See AL#91 pp. 6–13 for more on soundports.) While a hole in the side of the guitar might or might not directly affect the way the top and back (the main sound-producing surfaces on most guitars) vibrate, it could certainly be expected to affect the vibrations of the air inside the box. I became interested in this when a customer asked if I could build a guitar with a port. Since I’m the sort of guy who likes to have a map when I’m going into new territory, I looked up what information I could find. There was a certain amount on air resonant modes, but not much treating ports, so I decided to do an experiment. 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 June 6, 2024May 23, 2025 by Dale Phillips Questions: Jig for Oval Rosettes Questions: Jig for Oval Rosettes by R.M. Mottola Originally published in American Lutherie #97, 2009 Greg Pacetti of Fairbanks, Alaska asks: I’m in pursuit of some kind of jig for oval rosettes. The Questions column editor responds: Probably the single best source of info on cutting oval rosette channels appeared in the American Lutherie article “Making Oval Mandolin Rosettes” by Jonathon Peterson, et al. (AL#41 p. 34, BRBAL4 p. 140). In it, seven builders describe their methods. ◆
Posted on October 25, 2021May 14, 2025 by Dale Phillips Geometric Design of the Stradivari Model G Violin, Part Two: f-Holes Geometric Design of the Stradivari Model G Violin, Part Two: f-Holes with Robert J. Spear Originally published in American Lutherie #94, 2008 see also, Geometric Design of the Stradivari Model G Violin, Part One: Mold and Template by Robert J. Spear Geometric Design of the Stradivari Model G Violin, Part Three: The Scroll by Robert J. Spear The Cremonese design for the f-holes of a violin, at first glance, would appear to be based on the same design philosophy as the body and to make extensive use of the golden section. A. Thomas King, in his article “The Cremonese System for Positioning the f-Holes” in The Strad, shows rather convincingly that golden-section divisions based on the distance between the pins on the body was employed to fix the location of the f-hole eyes, which further reinforces this idea. However, when it comes to f-holes, I would like to suggest that there are a couple of additional jokers in the deck. First, the late Cremonese f-hole is derived from an earlier system of design, and some of the important parts of the predecessor system remain in use; second, an entirely different modulus is used for the f-holes than for the body; and, third, little is based on the golden section. The Forma G violin, upon which my model is based, is not quite the longest violin Stradivari ever made, but it is the widest. The most notable increase in width is in the center bout, which has another direct impact on the design of the f-hole and its placement. King notes that there is a general method for most Cremonese violins and a specialized adaptation for Stradivari violins. King explained the rather unintuitive step of taking the golden section of the distance between the locating pins in the top as the modulus for positioning the f-holes. I have used his approach here because it has many good points of correlation, and because I found an additional correlation that has convinced me even further that his hypothesis is correct. 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 August 17, 2020May 21, 2025 by Dale Phillips Basics of Air Resonances Basics of Air Resonances by W.D. Allen Originally published in American Lutherie #1, 1985 and Big Red Book of American Lutherie Volume One, 2000 Stringed musical instruments with soundboxes typical of the guitar and violin families have many internal air resonances. The resonance with the lowest frequency is called the Helmholtz resonance, and its importance to the quality of the instrument is appreciated. The resonances with higher frequencies have been referred to by different names: higher Helmholtz, cavity modes, or standing wave modes. These resonances have been measured and documented for several different instruments, but there seems to be little information on their controlling parameters. The intent of this article is to give the instrument builder some understanding of the air resonances, what parameters establish the frequencies, and some insight into the potential for using this information to make better instruments. A minimum-math, pictorial approach with approximation and rounded-off numbers will be used. Showing the effects of the controlling parameters is the objective, not the absolute value of a number. 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 July 31, 2019May 23, 2025 by S Mc Herr Helmholtz’ Tube Herr Helmholtz’ Tube by Mike Doolin previously published in American Lutherie #91, 2007 See also, “There’s a Hole in the Bucket” by Cyndy Burton “Sideways” by John Monteleone “Three Holes are Better than One” by Robert Ruck Design innovator Mike Doolin tried an interesting experiment. Mike’s guitars have the distinctive double-cutaway feature and they don’t lend themselves to a port up in the neck/cutaway region for reasons of underlying structure. So Mike put one in the lower bout and very unexpectedly found his Helmholtz resonance had raised something like a major third. He felt that compromised the responses of the guitar. His solution was to “tube it.” The side was ported before I assembled the guitar. After gluing the back on, I realized the change in the Helmholtz when I tapped on the guitar with the port open. It seemed obvious that a shift of a major third up was going to radically change the sound of the guitar, probably killing most of the bass response. I knew that ports in bass reflex speakers are often tubes, where the longer the tube the lower the resonant frequency. I also knew that the tube could be either inside or outside the box. So I initially held a roll of toilet paper against the port, letting the cardboard core of the roll form a tube that extended the port. That dropped the main air resonance back down, showing me that I was on the right track. Then I turned a tube of wood on my lathe to fit the hole and experimented with the length until the air resonance moved less than a half-step with the port closed or open. I recall the port being 1 1/4" in diameter and the tube being about 2 1/4" long, but that’s just from memory. 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.
