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I have just finished my first classical, my second guitar all around and first guitar done solo. The problem i am fighting is an odd double tone on the D string. sounds more like a harmonic than it does a buzz, and it's noticeable even when played open. There's a slight amount of the same on the A string as well.

So far i have:
- ground the nut down a bit, since the strings are too low into the slots. I don't think this is the issue as i imagine the problem would go away when fretting, but it does not.
- checked all frets for high spots. found a few and cleaned them up but i think the tone has gotten worse, not better.
- cut the saddle break angle a bit deeper and made the landing (?) more narrow. This seems to have helped a little. Also rounded the transition into the break angle so it wasn't a sharp drop off.
- switched from normal tension strings to high tension. No difference.

I am thinking the problem is with the saddle, and will next try to build a new one. how wide should the top of the saddle be before starting a the break angle. If i had to guess, i'd say i have about 1 mm there.

I am thinking the saddle is the more likely culprit because the weirdness does not go away when fretted. Bad assumption? the tone also seems consistant up the neck though it gets harder to hear at the higher notes.

Any thoughts are welcome!

Thanks!
Rob

After thoughts.... it's a bolt on neck if that matters.
No truss rod (rethinking THAT one.)
I'll post a sound clip after supper...

First I always try a new string. also if you suspect the saddle make sure that with the way the string is tied you have a good break angle on the saddle. I have seen the knot pulled so tight that it was lifted a touch on the tie block and resulted in a a bad break angle. I intonate the saddles so the break is set for each string, byt my contact point is rounded over on both sides. The harmonic sound is usually the string contacting the saddle or nut in two locations while vibrating.

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Don't know if this would help, but in addition to John's comment, have you checked the tuners to see if anything there might be loose? While plucking the D string, you can touch each of the parts on the tuners to see if the noise stops. A loose tuner part can create a sound that you would swear was coming from some other part of the guitar and can happen on both open and fretted notes.

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Doesn't seem to be an issue with any of the tuners.

I can't seem to be ab;e to access my phone for some reason so no pictures or sound available at the moment.

The D string does seem to be tied a bit higher than the others and could impact the break angle. I did change strings after i altered the saddle so the increased tone could be the result. I will retie that one and see if there's an effect.

if that doesn't work, i will try thinning the contact point.

Thanks!

Rob

Corrected the tie, but it didn't help. Maybe slightly. Next i increased the break angle and softened the sharp edge but to no avail. think I will shim the saddle to see if that makes a difference, but my string height is ok at the 12th (4mm on the base, 3.5 treble) so i am not really expecting that to make a difference.

Then maybe i'll play with the nut end a bit... but not expecting that to help.

Try putting the D string in G string's place and G string in D string's place, to see if the problem is with the string or the location.

Also could try taking the G string off and running the D string diagonally from D string tuner to G string bridge hole and from G string tuner to D string bridge hole. Might help figure out whether the problem is at the nut or saddle end.

Take the strings off and add them back one at a time.

It sounds like “Sitaring”, at least this is what I call it. It happens when the string rests on a flat spot past the initial break over the saddle. It doesn’t take much to cause the problem. I ran into this on my first guitar. I was initially really bummed out but finally figured it out.

M

I agree with Michael. To help ID it you can slip a small piece of paper under the string at the saddle and see if it effects the offending sound. If it does, that's probably the spot that need tweaking. Quick and simple test.

One of my first instruments sounded like a cross between a sitar and a kazoo till I figured out how to properly make bridges and nuts. Funny thing was first guy that played it unfixed like the goofy sound, of course he was a banjo player and you know how they are, it was a banjo at least.

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Brian R, Wood Mechanic
N8ZED

I am almost certain that the problem is your nut slots being too low (which you stated in your first post). This almost always causes the string to rattle on the first few frets even when you are fretting that string. Try fretting the string and have someone dampen the string behind your fretting finger by lightly touching the string in a several spots. I bet the sound will go away. Solution is to raise the nut or make a new one.

Does it show up on every note, or just certain ones?

If fretting notes does not take the offending sound away it's not the nut.

If there are no flat spots on the saddle and you have at least 4 degrees of break angle and are not doing Townsend windmills it's not the saddle or break angle over the saddle.

Now we have it surrounded.

Replace the strings with a new set or better yet a new set of a different brand/type/sort of stings and see what you have.

We chase offending noises every day... ( often the cause is the Mexican restaurant next door and the fact that I just ate there...) and you would be very surprised at how often it's a bad string. So much so that we invested in a video microscope so we can take photos of the offending strings when we find them which can often be visual with bad or inconsistent wraps and then we show the photos to the client when we hand them their bill.

It's also possible that just by the luck of the draw you have a wolf note/tone where the natural resonating frequencies of the structure or part of the structure of the instrument are excited by the energy of a vibrating string in a specific frequency. That's a different matter and requires more investigation. In our experience wolf tones are not common but we have had this be the issue. Boycotting CNN doesn't work either.

As Hesh says, the usual wolf note would show up at a particular pitch, and may show up at that same pitch on a different string. Re-tuning the string to a different pitch would move the wolf to another fret. There are also a 'wolfs' in the broader sense that can be associated with the string itself. A bad string, one that is out of round or has an uneven winding, can produce more than one pitch at a time. This can also be a characteristic of a normal wolf that involves a lot of motion of the top at the bridge; the string will produce slightly different pitches when it's vibrating in different polarities ('vertical' vs 'horizontal' with respect to the plane of the top). Classical D strings in particular are prone to another type of wolf note, caused by the 'longitudinal' pressure wave within the string itself. When this matches the pitch of the seventh partial of the string pretty exactly there is a strong couple that feeds back into the transverse vibration. The partial is split into two pitches, and you hear a difference tone, which can sound like buzzing on every played note. Plucking the string exactly in the center (open string at the 12th fret) should suppress this, and could be a good test.

There are lots of things that can cause wolf notes. They can be very hard to isolate. Often, once you have done so, they are fixable, depending on how much you want to alter the guitar, and the cause, of course.

What I am talking about is when the nut slots are so low that the string is basically laying on top of the back frets when you are fretting up higher on the neck. This makes the back of the string rattle on the frets. So whether you are fretting or not fretting you get a rattle sound. I have seen this many times. But it is easy to diagnose.

I think this is called back buzz when fretting. The string between the nut and the fretted note will vibrate and can cause a buzz. This sounds more like a buzz rather than a ghost harmonic.

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Yes, back buzz. A properly cut nut slot and neck relief will not have the back frets touching the string so no buzz.

ok.... my classical guitar instructor thought that it was fret buzz so i went an bought a 16" fret leveler from stewmac and went at it. The last three frets we definitely higher so i leveled everything and it seems dead level now, but the buzz did not get resolved.

Next i tightened all the screws on the tuners.. no effect.

Next i put on a new saddle almost twice as high as the finished saddle. E String at the 12th went from slightly under 4 mm to 5.9 mm... no change. I also made sure the was a nearly knife edge on there and again no difference.

right now i have about 7/32 at the 12th to the TOP of the "D" string (The one with the most buzz).

I also checked the first 3 frets on the D string and have 2/32 to the TOP of the string at the first fret, 2.5/3/2 at the second and 3/32 at the 3rd.
is that enough rise? the strings will be closer when i go back to the finished saddle.

I am going to run out and get some baking soda and will use that with CA to fill the nut slot for the D string and recut the slot in case i went too deep. But i assume that regardless of how poorly the nut is, once i fret the string that should eliminate the nut as the cause as the tone is generated from the fretted fret onwards (no?)

I also loosened the first 3 strings and put a clamp on the fretboard and clamped it down to the top. I know i forgot to glue down the fretboard (Bolt on neck) so i am hoping that's enough to eliminate that as a source.

If it makes a difference... i notice the buzz is almost gone if i fret right against the fret, and the buss is strongest when fretted at the center of the fret. I can't think of a reason why this would be.

I will likely take it to a local repair shop to see if they can diagnose... unless i get som more good ideas.

To answer some previous questions/comments.

NOTE: As i type this... i think i want to try some of these things now, so i am going to send this NOW as is and then go down and try these. Will be editing this thread ass I go through them. Thanks for all the ideas!....


johnparchem - Right now i have a tall knife edge rounded towards the base of the guitar. I will try rounding both sides. i also changed the strings from regular tension to high tension strings. no difference.

J De Rocher - i have tightened the tuners with no difference.

DennisK - switching D and G strings and try using different bridge/nut slots. INTERESTING! I did not see this comment and will try that after i post this.
UPDATE _ Switchng the d string to use the G string slot making no other changes did not resolve. To me that eliminates the nut slot as the culprit and means it HAS to be the saddle. BUT... i tried the paper under the string trick and that did not change the buzz.... so what the hell does THAT mean??? OK, i guess i will move the D string to the G string position and see if the buss moves with the string, No t sure what that will tell me if it does. *sigh*
OK, so after moving the D string to the G string position i still get the buzz. There was none that i could hear when the G string was in the position.

ASSUMPTION... I may need a smidgeon of forward relief in the neck itself??? (Now i am regretting my decision not to put a truss rod in this...lol)
What i had read was to have the neck dead flat to the body at the joint. but i suppose i may not have used the same radius on the top?
My head hurts...


Clay S.- try putting strings on one at a time. I have loosened all the strings but the D string and the buss remains.

Michaeldc - "Sitaring" thats what i assumed at the start, but i don't think so now with the knife edge i have at the bridge.

rbuddy - i like the idea of the slip of paper under the string at the saddle... makes sense to me. will report results tonight.
UPDATE - Made no difference. see note under DennisK.

Barry Daniels - "...nut slots being too low..." > I Don't think so. Pulled the string out of the slot and let it rest on top of the nut. The buzz is there when fretted. Also, your comment about the vibration of the string on the back frets, i damped that side and it did not stop the buzz so i think "back buzz" been dismissed.

Alan Carruth - the buzz is most prevalent on the first 7 frets, gets a bit too hard to hear higher up. It does get stronger in certain places, ;ike the 14th is a strong buzz. BUt i have gone over the entire fretboard with the stewmac fret leveler and using the string action guide does not rock across and 3 frets. Yeah i know it's not a precise instrument, but i think it's a decent indicator and i get no rocking anywhere....

Hesh/Alan - Yes i did change strings. Went to a higher tension set and same issue. I am not really familiar with wolf tones... I thought that was more when harmonics damped or enhanced waves at a frequency causing the sound to be enhanced or dampened? This is also not isolated to a single fret...
ALAN - when plucked at the exact midpoint, the dual tone is still there and the buzz may be suppressed, but it may just be the more mellow tone one gets as the string is plucked above the soundhole.


Conclusion so far.... the only thing that i can think of that has not been eliminated is that my neck angle is off.... the problem with that is i think the issue would be consistent for all the heavier strings, but the E sounds fine, the A only has the issue slightly (sometimes imagined!) and the issue is mostly limited to the entire lenght of the D string.

I have a third set of strings, a bit pricey at i think i paid $24 for , but i had wanted to try them when i had this working. Maybe i'll go out nd but another set by another braND. Both the normal and hard tension were D'addario ProArte strings. I suppose it's possible that i had two bad sets, but i assume that since i was winging some of this stuff it's more likely me that is the culprit.

I will likely bring this to the next NewEngland Luthiers meeting.
Or maybe i'll visit Treavor Healy in Easthampton Mass who helped me with my first guitar.....


Thanks to you all for your suggestions. Any thoughts whether it could be my neck angle and how to validate that would be also welcome...


Rob

Robert, I gave you the answer earlier. You can tell if the nut slot is too low by fretting the string between the 2nd and 3rd fret. Then look closely at the first fret ( you may need a magnifying glass; I use an Optivisor). If the string is touching this fret then the slot is too low.

Thanks Barry. I just ran down to confirm and yes, there is space between the first fret and the string when fretted at the second fret. I was fairly certain this was the case as my classical instructor felt the action was a bit too high at the nut, especially on the treble side. I also verified that, since this is compensated at the nut, that there is room between the string and the nut where compensated when fretted (not bottoming out).

I can't see anywhere that you've measured the relief.

Hold down your D string at 1st and 12th frets and measure the gap between top of fret and bottom of string at the 7th. If there's no gap, or it's too small, then the string will buzz.

The assumption when building is that the string tension will pull a small amount of relief into the dead flat neck, but maybe your neck is very stiff.

Others will be able to tell you what relief you should be looking for, and how to achieve it if it's not there (one option is to clamp a slight back bow into the neck and then level the frets, but this might not be right for your needs).

Of course it might not be the relief, but if you don't check it we'll never know. If you don't have feeler gauges, then standard printer paper can give you a rough check - can you slide one thickness under at the 7th? Two?

I can definitely see a gap with my optivisor. The thinnest gauge i have is .010 and it hits the string. tough to tell how many slips of paper fit. 4 seems to be .010 on my cheap calipers and they slide under but there is drag. 3 seems to be the limit, so that would be somewhere around .0075? is that enough?

I also just fretted at the first fret and checked for space at the second, and it's comparable to what i saw at the 7th...(12th was not fretted.) SO i am thinking the neck angle is OK.

One thing i noticed... the angle of the strings over the saddle is 17 degrees., but because i used a taller saddle for my test it made the angle stronger and even though i have a knife edge, it still looks like the string is resting on the back of the saddle. i think i will flip the saddle around and see if that makes a difference...

A couple of things. Neck relief is not related to neck angle. Seven thousandths of an inch of relief is good.

Also, you do not want a knife edge on the saddle. Round it over the entire top of the saddle. You do want to have the string contact the back edge of the saddle as well as the front edge.

Thanks Barry. I used a knife edge to make sure i got rid of the question of double vibration on the saddle, but i don't think i accomplished that. I flipped the saddle around so now there is definitely only one point of contact and i still have the double tone. *SIGH*.


BUT Now i have a new issue... i managed to knock the dang thing off the bench and cracked the back. Starting a new thread on that. double tone. still there. I think i need to bring it to the NEL meeting and see what i am missing.

Hi Robert,

First, my disclaimer: I'm not a highly skilled and experienced luthier, just an amateur who's built a couple of guitars. Probably less experienced than you. So this may be a dumb suggestion and you should take it with a large shaker of salt.

I wonder if it's something other than a string that's buzzing. On one of my builds I had a weird buzz that turned out to be the truss rod. A little tension fixed it. I know you don't have a truss rod but maybe there's some other reason for some part of the guitar to vibrate unhelpfully. So I was wondering if an experiment could show that. If you're set up for Chladni testing maybe you could remove the strings and search for some frequency that excites the unwanted noise. If you don't have that setup and you do bring the guitar to the next NEL meeting, you can let me know and I'll bring my little amp/speaker/iPhone setup. Or you can come to my shop (in Hopkinton, MA) and try it there.

After you've fixed the back, of course. Wouldn't it be interesting if the noise went away after you fix the crack... Probably not very likely but I suppose it would leave you scratching your head if it did happen.

Now the relief has been checked, you seem to have covered everything string-related.

If so, it must be sympathetic vibration. You've tried all the outside, so that takes us inside the box. It could be a wood shaving glued to the back of a brace. More likely a short length of a brace where the glue has popped. I once found one of those after a few hours trying everything else by playing the string while pressing on the base with a stick with a padded end. Check the linings that way too. Once you've fixed the crack, obviously, in case that fixes the buzz as a by product.