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.
Posted on June 6, 2024May 22, 2025 by Dale Phillips Letter: Kenny Hill Responses in AL#98 Letter: Kenny Hill Responses in AL#98 by Alan Carruth Originally published in American Lutherie #100, 2009 Tim — I found Kenny Hill’s response (in AL#98) to R.M. Motolla’s study of ports (in AL#96) interesting. I’m not going to answer every point he made; some are more properly addressed by R.M. himself. However, there are a couple of things I would like to comment on. Kenny wrote: “I’m guessing that Al’s cool Corker was not really constructed as a concert instrument, that it does a good job at its original intended purpose but was not built to prove or disprove the validity of soundports as a useful design element.” I think the concept of what is or is not a “concert instrument” is slippery enough that we won’t settle it here. Nobody is likely to appear on the stage with something as rough as the “corker” so that in itself excludes it from that class. I will note, though, that several people, including one very fine maker, have remarked that it is at least “not bad”, and R.M. told me that most of the players had a much higher opinion of it when they were blindfolded. 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 6, 2024May 28, 2025 by Dale Phillips Questions: Book on Acoustics Questions: Book on Acoustics by Tim White Originally published in American Lutherie #73, 2003 Lee Parks from cyberspace asks: I just need to know a good book that teaches fundamentals of acoustics for guitar construction. Tim White of New Boston, NH responds: The GAL has published many articles over the years but the only “book” I know of is the one I put together — Journal of Guitar Acoustics, from seven issues of the Journal of Guitar Acoustics, originally published between 1979 and 1982, which includes the complete collection with addenda, 700+ pages. The Evan Davis thesis bibliography alone makes it worthwhile as an entry portal to the strange world of guitar acoustics. The republished single volume has an updated bibliography and additional material. It can be ordered from me at: 146 Lull Rd., New Boston, NH 03070; 603-487-2696; tpwhiteco@aol.com; www.chrysalisguitars.com/JGA_Page.html. ◆
