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 30, 2024May 14, 2025 by Dale Phillips Practical Acoustics Practical Acoustics from his 2008 GAL Convention lecture by Michael Cone Originally published in American Lutherie #102, 2010 Nikola Tesla said, “Science is but a perversion of itself unless it has as its ultimate goal the betterment of humanity.” On the one hand it’s only a guitar, and the jury is still out on just how much better off humanity will be for having a better guitar. On the other hand, a musical instrument is the conduit between a musician and the divine, with the capability to inspire and transcend our ordinary, relative existence. This by itself certainly makes lutherie a worthwhile endeavor, and the application of science to this art and craft, an ultimate necessity. By science, I mean repeatability, not theory. I mean the practical application of measuring, changing, remeasuring, and then seeing and hearing the difference. We’ve been doing the same thing for several thousand years: flexing, tapping, training our ears, training our guts. After twenty years or so, you pretty much know what you are doing. 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 30, 2024May 13, 2025 by Dale Phillips It’s All About the Core or How To Estimate Compensation It’s All About the Core or How to Estimate Compensation by Sjaak Elmendorp Originally published in American Lutherie #104, 2010 Ever since I started playing guitar, I’ve wondered why the saddles in my steel string guitars were set at some magical angle and, more puzzling, why the B string in my Martin D-28 (well, a cheap Japanese replica I have had for forty years now and still outbooms any guitar you want to bring to the bonfire) was about 10% sharp. After having accepted that this was one more quirk of the guitar-building community I had since joined, I got intrigued again when I set out to build a long-scale nylon-string acoustic bass (Photo 1) and, for the life of me, didn’t know what compensation to use. The physics of the problem is very straightforward, but I found the mathematics employed to date rather inaccessible and the recipe for applying the developed theoretical frameworks not very clear. Given the fact that I once was a practicing physics PhD, I had to assume I wasn’t the only one wrestling with the question. Over the course of a long e-mail conversation with R.M. Mottola, for which I am very grateful, I was beginning to see some light at the end of the tunnel. 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 28, 2025 by Dale Phillips Questions: Measuring Guitar Efficiency Questions: Measuring Guitar Efficiency by Alan Carruth Originally published in American Lutherie #73, 2003 and Big Red Book of American Lutherie Volume Seven, 2015 Buck Montoya of Wichita, Kansas asks: I’ve heard and read that acoustic guitars are horribly inefficient (less than 10% if I remember correctly). Is there a method of measuring a guitar’s efficiency that could be performed by the average luthier without the resources of a fully equipped lab? Al Carruth of Newport, New Hampshire responds: I think most instruments are pretty inefficient. Neville Fletcher and Tom Rossing discuss this in their book, The Physics of Musical Instruments. The figure that I’ve been given for the violin is about 2%, and Ervin Somogyi said at the GAL convention in ’92 that guitars run around 5% efficient. It’s not easy to measure the efficiency of a guitar. For one thing there is so little power involved: any source of noise will throw the measurement off. For another thing, guitars are complex sources: even the headstock radiates some sound. You have to take measurements all around at all different frequencies and add them up to find the total. And you can’t take the measurements from close up, since the phase cancellation of the different radiating areas can skew the results. The cheapest calibrated microphone and preamp combination I know of costs several hundred dollars, and it’s probably the wrong kind of mike for this. I wish it were an easy measurement to make: I’d love to know how efficient my instruments are. But try as I might I can’t think of an easy way to do it.
Posted on June 6, 2024May 28, 2025 by Dale Phillips Questions: Measuring Soundboard Vibration Questions: Measuring Soundboard Vibration by Alan Carruth Originally published in American Lutherie #73, 2003 and Big Red Book of American Lutherie Volume Seven, 2015 Gregory Furan of Toronto, Ontario, Canada asks: Over the past several years there have been numerous articles written in many different guitar mags regarding measuring soundboard vibration, that is, tuning tops. Can you give me a reference for where all of the different elements can purchased? Al Carruth of Newport, New Hampshire responds: For tuning plates on guitars or violins, the equipment you need is fairly simple: a signal generator capable of producing a reasonably “clean” sine wave signal over the range from about 20Hz to 1000Hz, an accurate frequency counter, an amplifier that can boost the output of your signal generator to around 12w or more, and a loudspeaker that is matched to the amp and rated for the power. To be on the safe side, I’d get a speaker that was rated for about 1½ times the nominal power of the amp: sine waves have high peak-to-peak voltages. 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.
