Official Luthiers Forum!

Need advice and help.
I am not a luthier, own some guitars three of them built by my trusted luthier and friend Lukas Milani.
Now I got a brand new acoustic crossover guitar. When fretted in the middle of the fret, almost 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.
We put 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 this way 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 the saddle and the point where the finger press the string; this 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.
No change plucking with a plectrum, nor varying the angle of attack to the strings playing with nails. No change with high tension or normal tension string set.
Any ideas?
Thanks to anyone for your time.

I'd suggest checking the top of the saddle again. If it is not properly rounded over, but has a ridge, then at certain fret positions there will be a tiny gap between the string and the ridge, enough to make your guitar sound like a sitar.

If this is the problem, gently sanding to remove the ridge should fix it.

[quote="profchris"...at certain fret positions ..../quote]

Unfortunately the parasite tone sounds at any fret of the fretboard and any string

If the ridge is in the right place it could affect all strings at all positions.

But your original post says the problem is more or less intense, depending on which string you play and at which position.

In any event, it will take you only two minutes to check this. Loosen your 4 and 5 strings, which are the worst offenders, and gently run your fingertip over the top of the saddle, stroking it from front to back (or back to front if you prefer). If it feels silky smooth, that's not the problem. If you feel a sharp edge, no matter how tiny, or a dip, or any roughness, that might be the cause.

Eliminate this first, because from your description it's by far the most likely cause of your problem. If the saddle is shaped so that, as the string vibrates, it also hits a second point on the saddle, then it will ring out as two notes, one slightly flatter than the other.

I assume this means between the frets and if so the other replies might not be addressing the problem.

Fred

_________________
Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Yes I meant between the fret wires (or name fret bars).
Say you're fingering an E chord on the first 2 frets: you will have the tip of your mid finger on the 5th string about in the middle of the 2nd fret, between the two fret bars, and that string will sound with the "parasite" tone; while the tip of your annular will be on the 4th string just close to the fret bar, and it will generate a clear tone. This happens on all the frets all along the fretboard. The "parasite tone" can be heard more or less louder: more on D and A strings, much less on the E-B-G strings but still audible, almost not audible on 6th string.

Sounds like a technique issue. You kind of answered your own question by stating that as you play closer to the fret it goes away. My answer would be to work on just playing closer to the frets instead of right in the middle.

If it's really a problem, try muting the strings behind where you play them with a hair scrunchie or a capo or something and see if it's still present.

I take Fred's point, but the mention in the original post that it sounds like two guitars, with one slightly flat, suggests that it's not a resonance from the string between fret and nut (that would be substantially sharp, at lest up to the 12th fret). I've had the saddle problem, which sounds just like this, and it changes depending on how you fret the note.

But diagnosis via the written word is near impossible ... The obvious first step is for Woodfellow to rule out the saddle in the way I suggest, and to rule out back resonance by damping the strings between fret and nut. These will take him only five minutes.

If neither identifies the cause, then I suspect we need a sound sample to help us advise further, but these problems are almost always an extended trial and error process to diagnose.

Update.
Assumed, as absurd as it may sound, that the guitar is too much responsive, and that an exceeding amount of energy is driven back from the saddle to the fret, the bone saddle was substituted with an ebony saddle. Well, no change in the generation of the parasite tones, just a (little) fall of high frequencies as it could be expected. So, is this a too much responsive guitar ??
Yet I'm not a luthier, but i must confess that this issue is shaking much of my knowledge about physics and reality.

How is the guitar too responsive? Most try their entire lives to build highly responsive guitars. You either have a technique issue or you're not giving us the entire picture. What did you try that makes you think that it's too responsive? What brand of guitar is it?

Can you possibly put up a video of the issue?

Yes, information on the make and model of guitar, along with a video showing the guitar played, in a normal playing position with accompanying audio so we can hear the "parasite tone" would be most helpful. Before producing the video/audio, change to a new set of strings of a brand you trust and are familiar with to remove the variable of defective strings from the equation.



To clarify, are you saying that the second "parasite tone" you are hearing is almost, but not quite, an octave above the note fretted?



For my part, I'd prefer to discard this assumption about what is happening and where the tone is coming from until I've seen/heard it for myself.



Guitars occasionally produce unexpected sounds that may at first seem mysterious. However, there is always an explanation - we don't need to begin reevaluating our scientific understanding of the universe just yet.

I have had a few classical guitars on occasion where a brace had cracked/broken ever so slightly and was vibrating inside the guitar. Have you checked inside to see if that could be the issue?

The guitar is still now at the laboratory of the luthier who built it, so I cannot make any video.
But, listen to what the guy who had exactly the same experience back in 2013 and describet it on another forum says today (I wrote him hoping to get good news....):

"All you folks giving the op grief about it being his technique need to zip it. It is absolutely not his technique. It is NOT the kind of buzz you get if you are in the middle of the fret and not pushing hard enough. No, this is an unholy demon level buzz. I'm the one who started the other thread about this problem three years ago. Understand that this is not just your normal buzzing. It is almost as if a secondary note comes through. The Paul Mcgill article is a perfect illustration of the problem. As the article states, if you move even 1/8 of an inch from the fret this problem can appear. There is no way in all hell that every single finger on every single chord can be played 1/8 of an inch or less from the fret. The op does not sound like a noob when it comes to guitar, I'm not either. I teach guitar all day every day, have taught almost 40,000 lessons, do repairs and setups on the side, etc., this problem is as strange as they come. What Mcgill says is correct. The note j
ust "accelerates" off the fret, almost as if it is oscillating too rapidly or something. I was driven mad by this problem on a Cervantes Crossover. Had it worked on by the best repair guys around. Never got solved and ended up sending the guitar back after many weeks of trying everything we could think of. Bought a Kenny Hill and no issues.

It was literally the most frustrating problem I've ever had on a guitar in my 25 years of playing. I have owned dozens of guitars, but none had such a problem as this Cervantes. I've had back buzz problems, fret buzz, etc., and I always was able to fix those issues, but the demon buzz defeated me and was never solved. **** shame too because the Cervantes felt great."

Gosh!

Find here some pictures of the building :
https://www.facebook.com/media/set/?set ... e8c4cecd8c

The gentleman you quoted seems to have a beef with someone and seems a bit angry, not sure what's going on there.

Let's look at it this way, you obviously have some experience with playing guitars. Is it possible that you have grown accustomed to how you play on your other guitars and this one is so different than what you're used to that it's causing issues?

I started playing on a nylon string and now almost exclusively play steel string, when I go back to a nylon string I have to readjust many things about my technique to get good tone, it's just a different animal entirely.

I think at this point until you can show a video of you playing that's kind of shooting in the dark to try to fix this problem. Once you get a video up of you playing and the mystery noise we can definitely help more effectively.

Curious if you solved your problem?

I have had this issue when I had frets that were not crowned properly. When close to the fret the string was pushed tight against a curved part of the fret. Away from the fret it hit the fret in two places on the leading edge and on the trailing side of the frets. That was why one of the resonances was slight flat. I chased it for awhile. I finally leveled all of the frets and recrowned them and it went away.

_________________
http://www.Harvestmoonguitars.com

It has been resolved on other forums that this is a zip tone, or longitudinal string resonance, and is more a function of the strings than the guitar or technique.

_________________
A man hears what he wants to hear, and disreguards the rest. Paul Simon

Well I recorded the "evil sound" and made a spectrogram, maybe you can compare it to the sound of your guitar at that time?
https://youtu.be/t9USFNMDs2I

Nope, not the same at all. It is evil. Amazing that besides the two tones that it had such a strong beat frequency. I saw above that it was a function of the strings, so did a change of strings fixed it?

_________________
http://www.Harvestmoonguitars.com

I just wanted to test the consequences of an extreme change in tension/density of the string. So I changed 4th 5th and 6th nylon core strings to low gauge (.010) 80/20 bronze standard steel core strings (overall tension load of the whole string set is about 48 Kg);. The 6th string had ever been trouble-free and so it remained. The 5th string lost the evil sound, while the 4th string did not but it became sensibly lower. But the only thing which seems to make the evil sound disappear, is fretting the string on a "fake" fretwire (a common iron wire inserted under the strings close to the real fretwire) 1,5 mm thick..... Well, 1.5 mm thick frets ?!? that's to say jumbo oversize frets, I wonder if that would be the definite solution and how much would it change the playability of the guitar...
I'm still waiting for some conclusions from Alan Carruth who kindly accepted to analyze the sound recording I made.

Thank you very interesting.

_________________
http://www.Harvestmoonguitars.com

Interesting information. Can you put up a picture of the frets in question? Just curious to see if something is immediately visible or not.

Hmmm...well, any significant difference between real fretwire and the fake fretwire could be in height or in shape. The fake iron fretwire was perfectly round, so after all I made some macros of the frets, aaaaand ....

6th string, 2nd fret
https://goo.gl/photos/rV26mprxd2ppQjtM9

5th string, 2nd fret
https://goo.gl/photos/aBxUSap4DM5efNke7

4th string, 2nd fret
https://goo.gl/photos/PwpGTUr17ZUm1m6B6

Interesting stuff. I'll be following for sure.