Extra-resonant note, on just one string

[David_Norton]

Calling on the Collective Wisdom here:

One of my flamenco guitars has a very pronounced strong note, in one place only. The "a" on the 5th fret/1st string is a whole lot louder than the G, G#, A# or B surrounding it. AND, the very same note played on the 2nd or 3rd string, or as an harmonic on the 4th or 5th strings, is in proper proportion to the rest of the notes. So it doesn't seem to be resonance-related in a direct sense.

The sound quality of this particular note is very good, I could wish the other notes all had this extra "oomph". The net result though is that I have to remember to back down on the right hand attack for this note on this guitar. Otherwise the line gets unbalanced.

New strings don't make a whit of difference.

Thoughts?

[Trevor Gore]

Have you tried looking for a resonance that's a harmonic of the played note? E.g if the problem is on A at 440Hz and you're plucking in the "normal" region (about quarter the fretted string length from the bridge) you'll be strongly exciting the string partial at 880Hz (or maybe 1320Hz if you're plucking near the bridge) which may match with a body resonance. You can look for peaks using a tap test and spectral analyser and check the mode shape using Chladni patterns. The thicker strings when fretted high might not support enough of the offending partial to give a problem.

[Robert England]

David, as I'm sure you know, tracking down resonances like this can drive you mad. Usually, there will be a weak note somewhere else on the fretboard, that "corresponds" in some sense to the strong note. If it's a body resonance, its as though the two are trading energy. I have a couple of suggestions. This one is a long shot: are there other guitars in the room or nearby when you hear this resonance? If so, try taking the guitar away, out of "earshot" of the other guitars. Guitars interact with each other acoustically, just to make a complicated situation even more complicated, and I've seen cases where strange resonances were due to a pair of guitars interacting, and neither guitar by itself had any problem. Also, you could try sticking a small blob of that putty-like substance that is used to stick posters to the wall remove-ably on the soundboard at various places to see if you can tame the resonance. If you find a spot that does the trick, just move the blob to the same spot inside the guitar.
Robert

[tanolonco]

david, i had this problem with a conde a few years ago and took the guitar to al carruth who diagnosed the problem with the "blob of putty" and resolved it by shaving some wood off a strut. the diagnostic/resolution offered by robert england is easy, the shaving, and more important, where and how much is far more difficult for us mere mortals. for supermen like al carruth it is probably easy. al explained to me the problem but to be honest i would butcher the explanation so i will just say there were many components of the guitar resonating at the same frequency and what al did was to lower the guitar's vibration from 440 to 436 or thereabouts so when the "a" note was fretted it would not be in synch with the body. i hope that is correct.

the problem with an over resonanting note is that once you find it/them it is almost impossible to not hear it/them and it can drive one batty when you do. the conde did it on the 4th and 5th strings. an hour with al resolved the problem.

[David_Norton]

Here's the answer, albeit strange. New strings OF THE SAME TYPE (D'Addario J46) didn't make any difference. Today I switched them to Savarez Corum 500 AR Normals, which are a thinner string, and the extra resonance went away. Weird, but glad it happened.

[Robert Webster]

Yep, the Savarez strings are substantially higher tension than the D'Addarios. Long story short, that extra tension moved the top modes down enough to keep a specific top resonance from creating a wolf note.

Bob

[David_Norton]

Bob: just trying to confirm. I had on D'Addario high tension, switched to Savarez normal tension. So it seems intuitively that the reverse would be true about the node, although it still shifted...?

[Robert Webster]

We live in a perverse world, David. James Lister posted comparisons of different tension sets from D'Addario, La Bella, Savarez, and Hannabach on this forum some time back, from which I draw my info. In that comparison, D'Addario high tension sets had a total of 86.9lb tension whereas the normal tension Savarez Corum sets had 92.5lb tension. By comparison, Savarez Red Card normal sets had 89.7lb total tension.

Bob

[Alan Carruth]

What Robert says is probably the case: changing the tension altered one of the higher modes that was more active at the high E string location than for the other strings. I once had a guitar develop a buzz on the third fret D on the B string, and only there. After several hours of tracking it down we finally recorded that note, and ran a Fourier Transform on it. The 3d, 6th and 9th partials all showed 'split peaks', so the string was interacting with a top resonance at around 880 Hz. It was easy enough to find once we knew what to look for. Fixing it involved removing a small amount of material from one top brace to move the node line at the bridge location a little closer to the B string, making it hard for that string to drive the mode. Stuff happens.

[tanolonco]

al--i hope i did not butcher what you told me years ago.

robert--to add to the confusion, d'addario measures at 648mm, labella at 655mm and hannabach does not give out such info--or at least they refused in the past. hannach superlow 815 are about the same tension as la bella medium 2001 classical. go figure! numbers are better than words with string tension

[Alan Carruth]

tanoloco wrote:
"al--i hope i did not butcher what you told me years ago."

No problem: there are a lot of ways to create a 'wolf' note, but usually only one good way to fix one once you've found it. The trick is to figure out what's happening! Once you do the solution is usually obvious. Usually....

[Mistamor]

Very interested to have found this topic. I had the same problem for years (1st string, 5th fret) on my very expensive guitar from a world renowned builder. In my case the extra resonance was not at all attractive, and was made all the worse as the other notes around it became increasingly beautiful with age. I tried about 6 different string makes; high tension, standard tension etc., but the dreadful 5th fret squawk would always be there. Sometimes, without any obvious change to its environment, it would inexplicably disappear only to re-emerge the next day. Earlier this year, fearing for my sanity, I sold the guitar. But since then my despair has turned to desperation as I find that my new guitar (different luthier, same country) is developing exactly the same problem.

Reference the earlier talk about Savarez, the luthier tells me he usually strings them up with Savarez Cristal high tension. I’ve just changed these to try Augustine Blue Regals (high tension), so maybe I should try something even harder. Any thoughts, beyond what’s already been suggested?

[Alan Carruth]

There can be some pretty complicated stuff going on at around A=440, which makes the fix for an 'off' note there a problem to find. Many of the best guitars I've made do have an output peak in that range, but you have to control it.

[Mistamor]

That being the case, and my luthier has not controlled it on his 1a model guitar, perhaps it's simply assumed that these resonances will fade with time and use. My previous guitar never showed any signs of settling down during the four years I owned it. Some people tell me it would have done, others quite the opposite. Was I being impatient or would I have waited forever?

[mikfik]

To Mistamor: Try the putty- It's harmless and you'll feel so much better after the wolf note has faded.
I am very nervous about sticking anything onto the top of a newly french polished top so when needed to track down strange problems I use a blob of the green putty that came with a Schertler transducer I bought many years ago. This putty is the best and it's available from places that sell Schertler gear and doesn't cost much.