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#1
07-10-2018, 02:09 PM
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General build question
To those of you who build guitars and see a lot of repair work, I'd like to ask a question. A friend recently has had issue with a dead zone on a boutique guitar. On one string, the A on fret 9 and a lessor extent 8 and ten, his sustain is as much as half of every other note on the guitar.
He has talked to three respected repair guys who say there is no cure. My question is this. Is there going to be somewhere on the fingerboard that to one degree or another will exhibit this? Do builders design to minimize, or place the spot in a less used note? Is it chance or a rare occurrence? I asked because another of the same model I played had the exact issue. I know other stringed instruments like the cello can have this issue.
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2007 Martin D 35 Custom 1970 Guild D 35 1965 Epiphone Texan 2011 Santa Cruz D P/W Pono OP 30 D parlor Pono OP12-30 Pono MT uke Goldtone Paul Beard squareneck resophonic Fluke tenor ukulele Boatload of home rolled telecasters "Shut up and play ur guitar" Frank Zappa 
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#2
07-10-2018, 02:21 PM
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That's known as a "wolf" note, and it is caused by the natural resonance frequencies of the guitar. The closer a played note is to a resonant frequency, the less impedance the top has to absorbing the energy, so the note is twice as loud for half as long. The loud part is mostly in the initial transient, so the abbreviated sustain is more noticeable. Builders do try to position the major resonant frequencies between scale notes.
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Rodger Knox, PE 1917 Martin 0-28 1956 Gibson J-50 et al
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#3
07-11-2018, 05:44 AM
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If it is a true wolf note it should occur at the same pitch on every string. Does it happen on the D at frets 3,4 &5 and the E at 13,14 &15? If not it is not a body frequency issue as the phase would reverse at frequency and not at a specific position on the FB.
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#4
07-11-2018, 07:19 AM
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Check for loose frets. If not tight in slots, CA glue can be used to solidly anchor them without removing and gluing them. I've come across this problem in the few guitars I built. (I'm not a pro luthier.)
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#5
07-11-2018, 07:45 AM
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F sharp is a common top resonant frequency, particularly on dreadnoughts with scalloped bracing.
I like to place the top resonance between notes....usually between F and F sharp on dreads.
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#6
07-11-2018, 08:00 AM
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And if it is a wolf note, as Brian mentioned it will occur on the same note anywhere on the fretboard, then you can fix that by adding mass to the top in the right spot. To do that you can use some blue tack putty and roll a ball about the size of a dime and place it in various places on the top till you find the right spot. You might need to make the putty larger and heavier. Once you figure it out then you weigh the putty and then make a spruce cleat the same mass and glue it in place on the inside of the sound board in the exact spot.
It can be tricky to track the problem down. If it is a body resonance issue then sometimes adding mass at the bridge will help. You might consider using bone bridge pins for example instead of plastic or even ebony. Other methods would be to add mass to the sides or change the sound hole diameter. In the end though there is a cure. It just depends on what the situation is. Chello's have this issue in particular because they are bowed. The good news is that you probably have a good guitar there. Wolf notes in guitars tend to only show up in very responsive ones, same with body resonant issues.
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#7
07-11-2018, 11:34 AM
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Repair people tend to spend their time on action/buzzing problems and structural and cosmetic repairs, and may not have a lot of expertise with acoustic issues. The exception would be the folks who do a lot of brace shaving, and that may not be the best route here either. Try to find somebody, often a builder, who is knowledgeable about acoustics. 'Wolf' notes can be hard to track to their lairs, but once you find the cause they're usually easy to fix.
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#8
07-11-2018, 07:05 PM
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Interesting. The guitar has already gone back to the builder with no resolution other than to live with it. They mailed the guitar back to him. He has placed a claim for refund with his credit card company.
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2007 Martin D 35 Custom 1970 Guild D 35 1965 Epiphone Texan 2011 Santa Cruz D P/W Pono OP 30 D parlor Pono OP12-30 Pono MT uke Goldtone Paul Beard squareneck resophonic Fluke tenor ukulele Boatload of home rolled telecasters "Shut up and play ur guitar" Frank Zappa
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#9
07-11-2018, 08:04 PM
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Truly skilled guitar techs and Luthiers tend to be two different people. Luthiers are rarely called upon to manipulate a Guitar’s character after the fact.
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#10
07-12-2018, 07:26 AM
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Hmmm Interesting. You know I mean if this ended up at the Supreme court or something a good lawyer would argue that a wolf note is inherent in any musical instrument and as such is an act of god. Was there some sort of trial period where he could return the guitar?
I'm surprised the builder is not aware of how to mitigate such problems. This is why I string up a guitar and keep it and play it for two weeks before I ship it out. And really as for wolf notes that's not even a long enough time. It's also part of the reason why the great Spanish builders used to build the guitars up in the white so they could tweak them as necessary. If this is a brand new guitar then in a few months he very well may just play the wolf right out.
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