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Post by Me&MyGuitar on Aug 25, 2016 22:28:18 GMT
Need advice and help.
I got a brand new acoustic nylon stringed crossover guitar. When fretted in the middle of the fret, all the strings but mostly 4th and 5th sound like if it were two guitars sounding, being one of them just slightly flat. When fretted just near the fret bar, tones come off perfectly clear.
- Fret bars were checked and slightly recrowned to make the top sharper;
- the fretboard is as straight and flat as a billiard table;
- the saddle is made of bone and it was checked, it's ok;
- there's no truss rod;
- spanish heel neck.
- Putting on the fretboard surface a taller fret to which the tang was filed off: no way, actually the "doubled" note was more evident, all along the fretboard, fretting any of the strings. Trying with taller and taller frets, the resonance becomes more and more evident!
It is quite clear that the secondary flat tone comes from the "secondary" diapason between saddle and the point where the finger press the string; this slightly flat parasite tone can be heard at the attack and peak, while it fades away at the beginning of decay so in the decay phase you can hear only the main tone.
Any ideas?
I waited for this guitar for almost one year, it is really beautiful (I will post some pictures); but still now can't play it!
Thanks to anyone for your time.
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richm
Luthier / Guitar Maker
Posts: 47 
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Post by richm on Aug 26, 2016 9:30:30 GMT
It could be that the neck is too straight. The neck will need a little bit of a curve in it to, called relief, to allow the string to vibrate without hitting the frets further along the neck. Another possibility is that the neck might be at a slightly different plane than that of the soundboard before the soundhole, so the fretboard appears to lift up past the 12th fret. This would make the strings touch the last frets causing strange resonances Good luck and I hope your problem is solved soon  |
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Post by Me&MyGuitar on Aug 26, 2016 12:16:08 GMT
Unfortunately this is not a "next fret buzz" issue, believe me. Next fret buzzing would have been recognized soon and easily worked out.
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francis
C.O.G. 
Posts: 2,482
My main instrument is: Whatever I'm building...
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Post by francis on Aug 26, 2016 13:48:27 GMT
Sounds like you have a resonance between the soundboard and another component (possibly) the back plate but equally the sides or ribs. If you hold the guitar against yourself while playing to restrict the back plate vibrations is the resonance still evident, same or lessened?
Another possibility is the relationship between the upper and lower bout airmass', try putting a piece of towelling into the upper bout area to change its volume?
Doesn't sound like a wolf tone as its a general problem rather than a particular frequency - which makes me think it's to do with the sound box...
Back to the maker for further advice is probably the best option.
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Post by Me&MyGuitar on Aug 26, 2016 15:03:10 GMT
Thank you so much for your contribution. The guitar is yet back to the maker; he has never met before such a problem; I will share with him any advice or idea I will pick from here there and everywhere  |
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Post by Me&MyGuitar on Aug 29, 2016 7:18:01 GMT
Well see what Paul McGill wrote about this problem:
"I had a classical guitar made by a notable maker in my shop once that would not stop buzzing. The frets were accurately aligned, and still it buzzed. This guitar was very lively and had great oscillation of its strings. After much time spent studying the problem it became clear that the noise disappeared if the note was played with the finger depressing the string right on top of the fret. If the finger was moved back even an 1/8th of an inch, the buzz reappeared. The strings had so much amplitude that the strings would accelerate right off the fret, causing a buzz even though everything was properly aligned. I raised the action, the buzz got worse. The owner said he liked bass wire on his guitars, so I installed huge bass wire in an attempt to eliminate the problem. I was skeptical, but after installing the larger wire, the noise was greatly reduced. It was still there if the player wasn't careful, but it was manageable."
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Post by alexanderreay on Sept 10, 2016 18:02:58 GMT
Finding ghost resonances can be a complete nightmare, I like the name you use for it.
What appears to be fret related issue may have nothing at all to do with the playability. Anything loose, nut or saddle angles can cause problems. Loose bracing or screws, frets. Anything. And it all sounds like it is coming from the soundhole. Don't be fooled, this is the entire point of a guitar. Bastard things that they are.
One thing I like to do when diagnosing is to play the same note elsewhere on the fingerboard, as the vibration is the same frequency sometimes it will replicate the 'buzz' and rule out a particular fret or string.
Firstly find how you can reliably replicate the problem repeatedly. Keep strumming, causing the buzz and push on all points of the guitar and strings, behind the saddle or above the nut, etc, trying to affect it. Back, sides, soundboard, neck, everywhere. Try to keep everyrhing else constant, playing position, attack etc. Check the saddle and nut are seated properly, may be worth checking the bottom of the saddle is flat and the slot is clean. Take the corners off the saddle with sandpaper if it is tight in the slot. Do it anyway probably.
Loosen the strings feel around inside while pushing on the top of the soundboard checking individual bracing for cracks or looseness.
If it has a pickup, you need to make sure it is all tight.
Good luck!
Tighten screws. Superglue frets in if they are right and you are confident cleaning it up.
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Post by alexanderreay on Sept 10, 2016 18:04:29 GMT
And tap the saddle down when you string it up again, bit of wood and the side of some pliers... Or something. Not hard, just firm.
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Post by Me&MyGuitar on Sept 10, 2016 19:30:13 GMT
Thank you. This is driving me crazy. Actually I call it The Parasite Tone, because it sounds just like a dissonant tone parasiting any note played all along the fretboard, especially on 4th and 5th strings. I put on the fretboard a "fake" fret wire, I mean a simple piece of wire kept in site with a rubber band, and fretting the strings on it it seems to me the "parasite" does not sound. I supposed that the problem was a longitudinal vibration of the string jumping over the fret so I thought a wider and higher fret could solve the puzzle. Would you refret a brand new guitar almost never played?
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Post by alexanderreay on Sept 11, 2016 19:21:15 GMT
A surprising number of brand new and expensive guitars actually do need re-fretted to correct them. Largely the fingerboard not being straightened after the neck is put on, or put on with the frets already in. Fretting, neck joints, truss rod, tension, construction techniques, that whole area is a minefield of problems.
There is honestly no guarantee re-fretting would correct your problem, though. If the frets are levelled properly, crowned and not loose why would it?
I am sure you shall update this once the maker has addressed it. I would be interested. I too have been driven to the very brink of a murderous rampage chasing horrid noises all day.
Then you fix it and can't decide whether it is still there, has it changed? Have I actually damaged my mind?!
Raising the action really high would be another test.
Changing the string or affected strings, as well.
The fake fret is an interesting idea but it loses a lot of constants, changed the sound for the better so still valuable, but you can't definitely say it is fret related as the vibration is likely to be deadened somewhat which will mute the parasite.
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Jo whoever he is.
