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 Post subject: Strange Harmonic
PostPosted: Tue Feb 23, 2016 9:31 am 
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Joined: Sun Mar 09, 2014 8:13 pm
Posts: 1309
Hi Guys,

I've run into a zebra that I can't figure out. I replaced the top on the classical. When I fret (any fret), the 4th and 5th strings, I get a strange harmonic. It's not fret buzz, it's definitely a harmonic. This harmonic only happens when I fret the string halfway between the frets; it's not there when the strings are open. This harmonic disappears as I fret more toward the fret, although on the 5th string, I can still detect a tiny bit. This harmonic isn't there when the strings are open. It doesn't happen with any other string, and it's never happened on any other guitar. It happens on every fret, but it diminishes as I reach 12th fret and beyond (that could be because the distance between the frets are less, meaning I'm fretting closer to the fret).

Yes, I know I should be fretting next to the fret, but I've never encountered this problem before. This is what I've checked:

1. It's not the nut
2. Action height is great; relief is good
3. Intonation is spot on, on every string, every fret and at 12th
4. Harmonics at 12th are spot on
5. Not a buzz, it's definitely a harmonic
6. No sympathetic vibration of another string
7. No loose braces
8. Bridge is very secure
9. Nut and saddle are squarely seated
10. I've checked and checked, there is no high fret; the frets are rounded and polished.
11. Neck relief is good

I thought maybe there was a high fret that was so slight that I couldn't find it with the fret rocker, but making a buzz that sounded like a harmonic, but that is definitely not the problem.

Has anyone encountered a problem like this, or does anyone have a suggestion on something that I've not checked? I find it weird that it's only on these 2 strings. If it was the weight of the strings, I would think it would also affect 6th.


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 Post subject: Re: Strange Harmonic
PostPosted: Tue Feb 23, 2016 10:22 am 
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Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5419
Location: Hegins, Pa
sometimes these develop like a wolf note. This may seem silly but try taping a small piece of wood or use silly putty at different places on the top. The braces and top may be working is such a way that they develop a harmonic tone at certain pitches.
I have had this happen on an early guitar. I now have a small piece of wood glued under the top to break that cycle.

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 Post subject: Re: Strange Harmonic
PostPosted: Tue Feb 23, 2016 11:32 am 
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Joined: Sun Mar 09, 2014 8:13 pm
Posts: 1309
tippie53 wrote:
sometimes these develop like a wolf note. This may seem silly but try taping a small piece of wood or use silly putty at different places on the top. The braces and top may be working is such a way that they develop a harmonic tone at certain pitches.
I have had this happen on an early guitar. I now have a small piece of wood glued under the top to break that cycle.

You know, I thought of a wolf note, but I thought a wolf note was a string on the guitar that produced single notes that were very loud compared to other strings. I didn't know it was a harmonic.

I'll do as you suggest; thanks John


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 Post subject: Re: Strange Harmonic
PostPosted: Tue Feb 23, 2016 12:35 pm 
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Joined: Sat Apr 10, 2010 10:50 pm
Posts: 2281
Location: Seattle
Do you still hear the harmonic if you dampen all of the strings except the one you are playing? I wonder if you are hearing a sympathetic vibration from one of the other open strings. In that case the body might be sort of tuned such that its resonance is able to excite an open string. With a classical maybe the G string.

Johns trick of adding some putty to the sound board might eliminate it.

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 Post subject: Re: Strange Harmonic
PostPosted: Tue Feb 23, 2016 1:12 pm 
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Joined: Sun Mar 09, 2014 8:13 pm
Posts: 1309
johnnparchem wrote:
Do you still hear the harmonic if you dampen all of the strings except the one you are playing? I wonder if you are hearing a sympathetic vibration from one of the other open strings. In that case the body might be sort of tuned such that its resonance is able to excite an open string. With a classical maybe the G string.

Johns trick of adding some putty to the sound board might eliminate it.
]

It's a great suggestion, so good in fact, I took off all the strings to make sure early this morning. LOL This was my first thought as well.

It's definitely on every note, up the neck on D string, unless I fret close to the fret (proper fretting, which I really need to do). The top is starting to open up and is really becoming beautiful, but I'd sure like to get rid of this weird whatchamacallit.

BTW, I can't reproduce it by playing any other note on any other string. From what I understand, a wolf note is a specific note, such as F#, which causes a sympathetic vibration in another frequency. Therefore, if I played the same note, on the same octave, on a different string, I could reproduce the wolf. This is strictly a string phenomenon. The 4th string is the worst, there's just a touch of the problem on 5, but you'd have to have my hearing to detect it. I tried changing strings, just on the off chance that I had a defective string, but it stays. I've also taken into consideration that I just had surgery, so my entire hand is very weak, but it happens when I capo the guitar.

I realized that this harmonic was vibrating, when I played an A chord. I heard a bit of an extra harmonic from 4. Whether right or wrong, I play the A chord by lining up my fingers, index on 4, middle on 3, ring finger on 2. Since I do this, my index finger is further away from the fret.

I've tried to find the vibration by placing a block of wood over every inch of this guitar. I even capo'd the strings so I could lay it in my lap to try to find a vibration that shouldn't be there, but no joy. The vibration isn't in the back or sides either.

I've tried dampening the tieblock, the bridge from both sides, under the strings, the sound hole, even under the small part of the fingerboard that extends past the top of the soundhole. Since I did that design in the fretboard, I dampened the depression and THAT's not the problem.

The neck is solid, the braces are solid. I don't think it's a true wolf; it disappears as I fret closer to the fret. But, what in the world could it be? It's kinda driving me insane, especially since everything turned out so great on the guitar. It's starting to have a WOW factor as it opens up.

I've also tried tuning it down to C, and the harmonic remains. I even thought it could be fretting out such a small amount, as to sound like a secondary vibration, so I checked all the way up the neck, every fret, but it appears all the way up. I scooted the saddle over, to make the action higher temporarily, as well as the other direction to lower the action. There's no fretting out when lowered and the harmonic remains whether the action is higher or lower.

Grrrrr

I guess I'll stick a block of wood on the back of the neck and headstock to see if that's where it's coming from.


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 Post subject: Re: Strange Harmonic
PostPosted: Sun May 08, 2016 9:11 am 
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Joined: Fri Apr 15, 2016 11:22 am
Posts: 94
Try a fishing weight pinched on the string between the nut and tuning machine?


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 Post subject: Re: Strange Harmonic
PostPosted: Sun May 08, 2016 3:54 pm 
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Joined: Wed Aug 13, 2014 12:14 pm
Posts: 942
Try modifying the saddle contact point ever-so-slightly and see if that changes anything.

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