At fret 12: The G str. isn't sharp. The A str.is flat !!

Construction and repair of Classical Guitar and related instruments
MarkInLA
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At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by MarkInLA » Wed Mar 07, 2018 5:22 am

I may have stumbled onto something I haven't seen tossed around; not to my knowledge anyway.. Most are familiar with and may even have your saddle notched inward under the G string. This is a wide spread correction method which I believe came about when players began noticing how horribly out of tune the octave interval formed between the G on the 5th string, 10th fret, and the G string, 12th fret is, causing them to beat wildly..But, I believe the A stg, 12th fret octave is FLAT, and not the G, 12th fret octave, sharp.. I checked this several times with my tuner.. The G divides correctly at 12, while the A is flat. If I am right, it means ALL those G notches in saddles are wrong and rather a tiny 'balcony' under the A string on same side of saddle is needed, to shorten and sharpen the A String !....Adding the 'balcony' shouldn't be too hard as tiny piece of bone or similar material could be CA glued to the front of the saddle some, say, 3/64"-1/16" (+-) thick.. Please let me know if you do or do not find this to be true. ..M

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by Martin Woodhouse » Wed Mar 07, 2018 11:31 am

No, the fact that your guitar does that doesn’t mean that ALL guitars are wrong. The first thing to try would be changing strings - it could just be a string problem. If that doesn’t help, and assuming that your guitar has a straight saddle (with no individual string intonation adjustment), then the saddle on your guitar is probably about 0.5mm to 1mm too far back relative to the fingerboard, so the intonation is about right for the G string, but the A is flat at the 12th fret (and the D string will be even more so). In that case, either the bridge or the fingerboard were glued on in the wrong place on your guitar. You should be able to fix it in the way you suggested - I’ve seen it done on another guitar which had the same problem. It would be better to make a new saddle (and nut, if you want to get the intonation as good as possible) with the correct intonation adjustment for each string.

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by simonm » Wed Mar 07, 2018 12:28 pm

@Mark

Search for intonation and compensation here. You will find lots of threads. Before you worry too much, ask yourself you need to consider if you would notice anything if you did not have an electronic tuner. One of my favorite quotes is from Marcelo Kayath. In a masterclass he says "you can never get a guitar in tune, you can only get it less out of tune." Everyone has a different tolerance and over time often become more aware of it to the extent that some people think their guitar has developed a fault over time whereas what has really happened is that their sensitivity to intonation has increased.

Most saddles that I have seen are not notched. Certain makers do compensate the saddles and or the nut for one or more strings but it is not hugely common.

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georgemarousi
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by georgemarousi » Wed Mar 07, 2018 1:11 pm

look at the material mentioned above to understand better.

It looks like you describe the same problem of the sharp G, only in your case your saddle (or it's alignment on the slot, it's shape etc ) looks more far from the nut than is should be , so you have a correct G and a flatter A at 12th fret.

note also that the higher the action @12th fret the greater the issue, as G string is thick (compared to the other nylon strings) so the more stretched the more the tone sharpens..

My advice is to find a luthier and ask for a new saddle, mentioning your intonation findings :)
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JohnB
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by JohnB » Wed Mar 07, 2018 3:10 pm

Mark, You only mention the A string as being flat at the 12th fret - does this mean that you find all the other strings in tune (within a reasonable tolerance) at the 12th fret?

In any event, before jumping to conclusions it is worth putting on a new set of strings, ones that have a good reputation for reliable intonation, e.g. D'Addario EJ45.
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guitarrista
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by guitarrista » Wed Mar 07, 2018 5:28 pm

MarkInLA wrote:
Wed Mar 07, 2018 5:22 am
I may have stumbled onto something I haven't seen tossed around; not to my knowledge anyway.. Most are familiar with and may even have your saddle notched inward under the G string. This is a wide spread correction method which I believe came about when players began noticing how horribly out of tune the octave interval formed between the G on the 5th string, 10th fret, and the G string, 12th fret is, causing them to beat wildly.

Well, the reason is more scientifically based than what you describe, which places a higher standard for both disproving the current theory and for justifying yours.

The g-string is the thickest nylon string, which makes it the one with most noticeable inharmonicity among the trebles (its partials skew sharp because the string is stiffer than the other trebles due to it thickness). An ideal string has only the restoring force to push it back toward equilibrium when it is displaced; a real string has a bit of an "add-on" due to it stiffness, which is proportional to the 4th power of its diameter. So that add-on force starts quickly becoming more significant as you increase the diameter a little, as in the case of the g-string compared to the e (or b) trebles.

This is the basic reason for making the g-string slightly longer (inharmonicity is inversely proportional to length and tension but we can't increase the tension for a given material or the pitch will increase).

So you theory, if correct, has to explain away the above as well as explain the mechanism by which all other five strings are flat given their characteristics and the physics of vibrating strings.

Because of all this, I am skeptical for now :wink:
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simonm
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by simonm » Wed Mar 07, 2018 5:42 pm

A P.S. to my post above.

If you want to read a bit more:

http://www.byersguitars.com/Research/Research.html for a summary
and this for the complete original article.
http://www.byersguitars.com/Research/intonation.pdf

And here too:
http://www.frets.com/FretsPages/Luthier ... pcalc.html

And of course there is loads more in the Gore and Gilet books.

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by MarkInLA » Wed Mar 07, 2018 10:27 pm

There are too many replies to try and respond to each. Most of you seem to be saying I'm wrong. True or not, no one said they actually carried out what I'd suggested. The 2 'Es' on my Cordoba C10 divide at the 12 fret, perfectly, as do the B, G and D. This is proof enough that the bridge/saddle are perfectly installed. But, the A is flat by about, say, 4-5 cents. Also, I did just put new strings on prior to this. All your explanations may be correct.. But, is your saddle already notched under the G ? If so, this would throw off the test results. So, those of you with no G-notch, please; make sure the guitar is in tune. Finger the A string, 12th fret, being sure you're pressing it straight down, not bending it at all. Is it not flat ? MARTIN (above). I never said "all guitars are wrong". Please read it again.

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by guitarrista » Wed Mar 07, 2018 10:45 pm

MarkInLA wrote:
Wed Mar 07, 2018 10:27 pm
True or not, no one said they actually carried out what I'd suggested.
Well, I did explain why I don't have to - science! :D
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by Martin Woodhouse » Thu Mar 08, 2018 9:38 am

Sorry if I misread your post, but you seemed to be trying to infer that there is a general problem with the way that guitars are set up, based on your experience of one guitar. You said "it means ALL those G notches in saddles are wrong”, implying that they would be wrong for all guitars, which could imply that you think all guitars are built wrong. Again; sorry if I misinterpreted your post. All I meant to say is that it’s impossible to make a general statement about intonation setup based on measuring one guitar with one set of strings.

Are you using carbon strings (e.g. Savarez Alliance or similar)? They seem to need less additional length for correct intonation than nylon strings, which could explain your problem.

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georgemarousi
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by georgemarousi » Thu Mar 08, 2018 10:35 am

let me add a couple of notes since we actually talk about setup and intonation of a classical guitar;

This is an equasion of many factors like the below that first come to my mind ( the principles generally apply to other guitar types too )
- the guitars neck (is it straight? )
- the exact placing of the frets, nut, saddle (the last two are easier customizable to some extent )
- the nut setup, both horizontaly and also vertically - the distance from 1st fret when we press between 2nd and 3rd - which should ideally be close to zero )
- the brand, type and thickness of strings used
- the players playing style
- the placement and the exact shape of the saddle bone which defines both action height and lenght of strings

So we see that close to "perfect" intonation that is the point is dependable on many factors.

the saddle shape ( which allows us to trim a bit the length of a string) that we mostly refer to here is only one of the factors.

given that the previous factors are "perfect" and given that one defines his/her own preferences ( set of strings, playing style, prefered action etc ) a good luthier (or somenone who really knows and is able to do) is able to approach the last factor ( saddle ) in conjunction with the nut setup to define the perfect height /shape for the intonation to be as close to perfect as possible ( always in relation to the preferences mentioned before ).
Last edited by georgemarousi on Thu Mar 08, 2018 3:18 pm, edited 1 time in total.
Paulino Bernabe Especial 2009
Ramirez 1A 1980
Pavlos Gypas 1989
Panagi Brothers 1970
Juan Martinez nr 55 2014 (the comeback)
Yamaha cg 110 1988 (the 1st)
--
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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by simonm » Thu Mar 08, 2018 10:50 am

MarkInLA wrote:
Wed Mar 07, 2018 5:22 am
..... I checked this several times with my tuner.. The G divides correctly at 12, while the A is flat. ...
I checked this on a guitar I have with me at the moment. I my case both are slightly sharp but the G is somewhat sharper. The strings are from an obscure source.

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by MarkInLA » Thu Mar 08, 2018 10:32 pm

Thanks for replies. I've never said I am with no doubt, correct. I said " I may have stumbled onto........" But, If there is no one out there experiencing this same phenomenon then I guess I am wrong..M

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by bacsidoan » Thu Mar 08, 2018 10:59 pm

MarkInLA wrote:
Thu Mar 08, 2018 10:32 pm
Thanks for replies. I've never said I am with no doubt, correct. I said " I may have stumbled onto........" But, If there is no one out there experiencing this same phenomenon then I guess I am wrong..M
There's one plausible explanation (among others). In most guitars without custom saddle compensation, the G and low E string are a little sharp at the 12th fret with the standard practice of moving the saddle back 2 mm from the nominal scale length; the other 4 strings are "in tune", i.e. less sharp. If for whatever reason the saddle was back a little more such that the G-string becomes "in tune", it stands to reason that the other 4 strings would become flat. In your guitar, the pitch deviation of the A-string is just a little more noticeable than the other 3 (D, B, high E). Measure the distance between the nut and the apex of the 12th fret and compare that to the distance between the apex of the 12th fret and the saddle. I suspect that the difference would be a little more than 2 mm, particularly at the A-string.

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Re: At fret 12: The G str. isn't sharp. The A str.is flat !!

Post by MarkInLA » Sat Mar 10, 2018 5:39 am

But sir, I'd already stated, my 2 Es, G, B, D, are perfectly dividing at their octave; TDC (Top dead center). They are !...It's the A that is flat by 4-6 cents. If I added a balcony of some sort I could sharpen it to TDC. And I have no doubt there are others with the exact same conditions..That's all. I'd like to hear from them... It's more like I may have stumbled onto a possibly overlooked negativity of the fixed-saddle-position guitars. And at the same time I am fine with being proven wrong. Just asking to check it out....

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