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I have been more carefully evaluating intonation on my one classical (flamenco) guitar that I have in hand. I find that, using fairly hard strings (Savarez Red's), that the guitar tends to play slightly sharp up the fingerboard, although the pattern of sharp notes is not uniform. I'm thinking this is a sign of being under-compensated? (i.e., I may want to go a hair longer on total scale length ?)

The sharpness tends to be accentuated when playing in dropped tunings.

My scale is 650 mm with 2 mm compensation and no adjustment string to string. No other compensation other than the nut is sitting to the side of whatever the fret saw kerf is when cutting the slot at the nut position - certainly less than a minimally compensated nut position.

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Jim Kirby
kirby@udel.edu

Try this. I learned it from David La Plante. Works for me. Not a great picture, sorry.

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Waddy

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The saddle is compensated. Hard to see it in the photo, looks to be about the G string.

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Actually it starts at the e and slopes back to the g compensation, then it comes forward, and slopes back again from the D to the E. Sorry the picture is so bad.

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Waddy

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Waddy,

Can you actually hear it...

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Thanks Waddy. That is all done within a standard 2mm saddle thickness? I'll give that a try. I'll be slow to report back - I'll be away at a conference this week.

For this set of strings, it seems like more compensation is needed across the board. I didn't have the same issue with the La Bella's that I had on it initially - 12th fret harmonics and fretted notes were pretty much on the nose. I may not have given it as close a look up and down the fretboard at that time, though.

Now the fretted notes are a little sharp, although the sharpness is worse around 2nd and third positions than at the 12th fret. Makes me wish I had another mm or two in the saddle width, so that a saddle could be tailored for each of the different string sets. (Or glad that I have a dull ear for pitch - I can't hear these errors.)

This is the guitar that you saw at John Hall's get-together.

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Jim Kirby
kirby@udel.edu

Actually, my saddle is about 2.5 mm. I use a radial arm saw to cut the slot, and leave it at that thickness. Seems to work perfectly for me.

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Waddy

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Sound Clips of most of my guitars

Jim;
go to http://www.byersguitars.com
hit the research link and do exactly what is printed there.
Works great everytime.

Mike

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Mike Collins

Thanks Mike,

I will attempt to get more deeply into this on the next one. My concern at this point is whether you can get this all sorted out for one set of strings (at least as close as you can with a straight saddle, a uniform 2mm compensation at the saddle, and no nut compensation), and then have it go astray when you change to a very different set of strings. My guess is yes.

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Jim Kirby
kirby@udel.edu

The amount the string goes sharp when it's stretched a bit depends on a lot of things, such as how slack the string is, the diameter, and the material it's made out of. The string makers all seem to use slightly different types of nylon, so differnt brands of string intonate differently. It's just another way for classical guitar players to show the steel string guys who the real wusses are.

On the last few guitars I've made I have tried out an angled slot rather then a straight cut slot. In theory this should help but to be honest my straight slot ones are just as well, or just as badly, intonated. I like to use thicker saddles for this very purpose.

I watched the Bogdanovich DVD on setup and string up out of his 10 DVD set, and he tapers the top of his saddle from e to E, the thickness of the saddle. He uses 651 mm to the front of the saddle. If you read Byers article, he says that if you use carbon or coated strings, the compensation will be different, usually less. I usually just short the fretboard by about a half mm, and then comp the saddle as I showed. Seems to come out pretty close to perfect.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

No amount of compensation will work for every set of strings and every tuning. As stew-mac warns on their fret caculator.....they only give an average. If you use average strings and average tuning it should be fine.
As I understand it....as a string gets closer to its breaking tension, it needs less compensation. By using heavier strings and dropping the tuning you're moving away from the breaking tension so your intonation is off.

Thanks again for all the suggestions.

Waddy, do you have the Bogdanovich DVD's? Provide a review?

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Jim Kirby
kirby@udel.edu

A given string, at a given length, will see the same increase in tension for a given displacement, no matter how tight it is to begin with. If the increase is 1#, and the string is pulling 10# of tension, that's going to make it go sharp. If you tighten up the same string so that it's pulling 15# of tension, the 1# increase is not so great compared with the tension, and the [pitch rise will be less.

Strings with a higher Young's modulus increase in tension more, all else equal: steel strings need more compensation because they don't stretch as much as nylon; they just get tighter.

The fatter the string, the greater the tension change, all else equal.

Plain steel G strings need _lots_ of compensation, because they are both fat and slack. Plain nylon Gs also need some, although, being nylon, they do stretch more and the tension rises less than the steel strings.

Jim,
If the sharpness is worse around the second and third position as you stated above, then you may have a problem at the nut end rather than the saddle and it is best adressed there.
Are your nut slots Higher than necessary?
Are the distances from nut face to the frets correct?
How sharp in cents are you at 1st, 2nd and 3rd fret and at 12th?

Jeff - I'll look at that - but not til Sunday, as I'm off to a conference. No one who has played the guitar complained about the action at the nut being high, but I'll check that as well as the nut to 1st fret spacing.
Thanks.

Jim

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Jim Kirby
kirby@udel.edu