Posted on June 6, 2024January 21, 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, 2024January 17, 2025 by Dale Phillips Questions: North American Wood Questions: North American Wood by Mark French, Ned Steinberger, and Alan Carruth Originally published in American Lutherie #94, 2008 See also, Questions: Nontropical Fingerboard Materials by Tom Theil Larry L. from the Internet asks: I’ve noticed that my choices in materials have evolved over the years to favor wood from North America. At this point I’d like to take the final step and eliminate all tropical hardwood. The two fingerboard materials that make the most sense to me are phenolic impregnated paper or cloth (Garolite, Micarta) and phenolic impregnated wood (Dymondwood, Pakkawood, Staminawood). I think I understand issues with machining these materials and fret installation, but I wonder how differential expansion/contraction with changes in humidity will affect the stability of necks with wood shafts and fingerboards made of these materials. Does anyone have experience here? Mark French from West Lafayette, Indiana responds: Any time you have differential expansion of two materials that are bonded, you have the possibility of large deformations. For example, one type of thermometer works by having a coiled bimetallic strip inside. When the temperature changes, the end of the coil moves a needle. 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, 2024January 21, 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, 2024January 16, 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 March 7, 2024May 21, 2024 by Dale Phillips Side Soundports There’s a Hole in the Bucket by Cyndy Burton A Discussion of Sideports, with Contributions from Kenny Hill, Alan Carruth, Roger Thurman, John Monteleone, Mike Doolin, and Robert Ruck previously published in American Lutherie #91, 2007 See also, “Sideways” by John Monteleone “Herr Helmholtz’ Tube” by Mike Doolin “Three Holes are Better than One” Robert Ruck Just in case we become too self-satisfied with our “discovery” of ports, Alain Bieber, in his article on lyra guitars (AL#88, p. 16), points us to the Neapolitan Gennaro Fabricatore’s ported lyras from the early 1800s. (Alain ported his own contemporary lyra guitar, too.) So we know prominent makers were putting holes in the sides of their instruments in the late 1700s, early 1800s. Many of us are also aware of Carleen Hutchins’ groundwork in the early 1980s. Her “Le Greyère” violin, with sixty-five sideports, has provided a wealth of data about violin resonances since it was made in 1982. She donated the violin to the National Music Museum in 2002. See some great photos of Le Greyère and a list of publications reporting on that research at collections.nmmusd.org/Archives/NewViolinFamily/Hutchinscheeseviolin.html. People are sensitive about putting holes in things. Many guitarists — perhaps more classical guitarists than others — find the ports some sort of denigration, a violation of the sanctity of the guitar’s perfect form. In all fairness, we’ve met with very strong feelings on both sides of the port issue. Luckily, our customer was very open to the idea. He’s not a concertizing musician, but he’s a serious player, and occasionally he plays publicly for special events. We wanted to try ports for him because he has a hearing loss, and we thought ports would be a great way for him to hear himself better. At that time, Robert Ruck had made about a hundred ported guitars, so we figured he had worked out the kinks. He kindly advised us on size, location, and so on. We followed his lead. The result is a wonderful instrument that the owner truly appreciates. We love the feedback — the monitor effect for the player — and when we tested it in a small auditorium with an overflowing audience, we could not discern any loss of projection or quality of sound. But was it louder? Our evidence was very meager and inconclusive. Many makers are adamant that it’s louder with the ports open for both the player and the audience. 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.
