Compensated Nut....Any experience?

[35' Sunburst]

As many of you have probably noticed some of your acoustics you tune to compensate for the idiosyncracies with respect to the nut for a respective scale length. Some times tuning your B and E down a tad. sometimes even the G string. Ever so slight but it does seem to help with the chording and sounding "in tune" especially with open chords in the first 3 frets. Even with a good set up you still have to slightly compensate.

BUT along comes the Compensated nut:

https://www.google.com/search?q=comp...IBigB&dpr=1.05

I mean the variables for this idea are almost endless.
Anyone try this idea with good results?
I mean it seems to make sense.
Take a look at this one:
http://flameguitars.co.uk/sites/defa...uction/Nut.jpg

I find this whole idea seems to be more of an issue with the 24.9" more than a 25.5" scale length.

Love to hear some view points on this.

[35' Sunburst]

Here's an example with respect to a 1 11/16 nut width.
Check out the explanation in the description.
http://www.ebay.co.uk/itm/Earvana-Sh...CCZ5Xmn8-veMhA

[Tom West]

The Trevor Gore books have quite a bit of good info. In my mind standard width saddles are a bit of a compromise in terms of what can be accomplished at the saddle end. A wider saddle and nut compensation give the best intonation I've been able to accomplish. Still not perfect, but more then enough for my ears.No doubt others will differ.
Tom

[35' Sunburst]

And then there is this video:
https://www.youtube.com/watch?v=a-TxGkG6jJY

[Alan Carruth]

I've been using nut compensation for several years now. As has been said, there is a good explanation of it in the Gore/Gilet books, and as Trevor points out, once you try it you may never be satisfied with an uncompensated nut again. It is probably not possible to make a guitar with straight frets that plays perfectly in tune on all notes, but you can often get 'arbitrarily close'' with proper nut and saddle compensation.

Shorter scales need it more for the same reason that they 'bend' easier. Displacing the string raises the tension. The actual amount the tension goes up depends on how much the string is displaced, as well as the material and structure (wound or not, with what, and so on). The tension rise does not depend on how tight the string is to begin with. A shorter scale gives the same pitch with lower tension, so a given displacement, which causes a set rise in tension, gives a larger percentage change. A short string might be carrying 14# of tension (just pulling numbers out of the air here), while the samme string on a longer scale might pull 18#. If the tension rise is 1# in each case that gives a larger pitch shift to the shorter string. It 'bends' further for a given displacement, and requires more compensation at both ends to play in tune.

[35' Sunburst]

Thanks for the reply's and Book info.
I really have become a fan of my newly acquired Gibson L00 but I have to say the intonation is just even so slightly off enough, If I'm going to be super critical (even with compensated saddle) to explore the compensated nut.
I really enjoy the guitar but with fingerstyle playing you want those notes to be a close to in tune as possible in all positions.
I'm going to give this some serious thought.
Thanks again to the info.

[Laughingboy68]

Recently had my Martin OMCRE refretted by Michael McConville in Stratford, Ontario. He also fitted a compensated nut. Magical change to my guitar.

[B. Howard]

I have installed a few Earvanna nuts over the years and yes they make a difference. But not enough of a difference for me to use them on my builds.

They seem to color the notes slightly differently than what we are used to hearing. Not unpleasant, not necessarily better, just different to my ear.

I took a workshop with someone from Earvanna years back where they had several guitars with standard nuts and matching set bridges that could be swapped in 30 seconds and we could listen to them virtually side by side
on the same guitar. We also went over them with a strobe tuner and plotted the differences in pitch at various frets. My conclusion is that they have the greatest effect in the first few hand positions, as you move up the neck the effect is less. The change in color of the note I hear seems to be in the fact that on a standard set up most notes ring a few cents sharp but with a compensated nut more of them start to ring a few cents flat......

My final thoughts, A well made and set up guitar with the nut slots cut to the proper depth and the saddle properly positioned and intonated will be true to pitch within 7 cents at every fret, with a compensated nut and the bridge now set appropriately for that set up will be within 4 cents of pitch.......Most of us cannot hear that minute of a difference. You must also remember that adding intonation at the nut requires re-intonating the bridge which is not as easy on an acoustic as an electric and will often require moving or widening the saddle. Perhaps this is part of the reason that several electric makers use them as OEM but I don't know of a single major brand of acoustic that does. A lot of production acoustic guitars do not have their saddles positioned properly or cut for good intonation to begin with and simply adding a compensated nut will not cure this.....

[35' Sunburst]

Thanks for your input Brian
The concern I have is when you go to an alternate tuning which I use regularly - the tension changes for the same scale length for the respective string so the whole idea gets thrown off a few cents for that reason....
Oh well it was an interesting study anyway.

[Alan Carruth]

My understanding is that the Earvana nut comes with certain compensations built in. Ideally, to get good results, you need to set the nut up for the strings, action height, and scale length you're working with, so a one-size-fits-all approach naturally won't be as good. I set up a 12-string a few years back with individual compensation for each string at both ends, and got everything within three cents all the way up. It got rid of the usual 'crunch' that you get with 12s as the octave strings beat against the regular ones, and everything goes to pot further up the neck.

Keep in mind that we're normally setting the guitar up for 12-tone Equal Temperament. It's the 'natural' system for a guitar, since it's the only one that uses straight frets. Mathematically it's impossible to construct a scale that has both octaves and fifths that are truly consonant, and we've gone with ET not because it's sweeter than other systems, but because it works better for Western music. One of the drawbacks with it is that some intervals, such as the third, are pretty far off from 'ideal', which means you get a lot of beating between notes. If the intonation is off, that can just add to the problem. Anything you can do to get things closer usually helps, and nut compensation does that.

[Ned Milburn]

Myself, I haven't experimented much yet with compensated nuts. But I have had an occasional guitar come into my shop for maintenance or repair that is fitted with a compensated nut. One I remember well was a flamenco guitar that intonated so poorly we put in a conventional nut and the problem went away.

Saddle compensation is more important than nut compensation.

[dekutree64]

Originally Posted by Ned Milburn

One I remember well was a flamenco guitar that intonated so poorly we put in a conventional nut and the problem went away.

Were the saddle contact points moved as far forward as possible without enlarging the slot?

Every mm of nut compensation toward the 12th fret needs a matching mm of saddle movement toward the 12th fret (starting from the normal saddle-only compensation points). Otherwise the 12th fret note versus 12th fret harmonic will become unmatched. The end result is that you need far less saddle compensation than usual if you use nut compensation.

[Alan Carruth]

What dekutree64 says.

Basically, when you fret a string you stretch it a bit, and that shifts the pitch up a little. If you set up a guitar with everything 'perfect' according to calculated measurements, and check the pitches of the fretted strings carefully, you'll usually find that they're a bit sharp on the first fret, and go sharper as you go up the neck. Plotted on a graph of 'cents sharp' vs 'location along the string', with the nut on the left and saddle on the right, you get a line that starts off low to the left and rises.

To get the pitch correct on the first fret you could shift it back a little toward the nut to flat it. Then you'd need to shift the second fret back, and so on. It turns out that if you shift all the frets back by the same amount (say, 2mm) you get the same amount of flatting on all the notes; the line shifts down by the same number of cents for each fret. Shifting the nut forward and re-tuning the string is the same as shifting all the frets back.

Shifting the saddle back doesn't make much difference in the pitch of the note on the first fret, since it makes only a small proportional change in the string length. It makes more of a difference as you go up. Thus the effect of shifting the saddle back is to flatten out the slope of the line. If you leave the nut in the 'theoretical' position, and shift the saddle back you can get the fretted note at the 12th fret to be exactly one octave above the open string pitch, rather than a bit sharp. It doesn't help things to play in tune in the first position, and should, in theory, make the notes above the 12th fret a bit flat.

Shifting both the nut and the saddle tends to give the best result. You shift the nut forward enough to get an exact semitone when you fret the string at the first fret, and then shift the saddle back to get an exact octave at the 12th. In theory this should give a flat line at zero sharpness, since you've worked with both ends.

In practice, on real acoustic guitars, it's not possible to get that. Resonances of the top and air cause the soundboard to move, and shifts the pitches of notes near those frequencies. Note, too, that the exact degree of sharpening of the notes is related to the characteristics of the strings, the action, and so on. In practice, then, each string will probably need a different amount of compensation at each end (and maybe even none at one end or the other!).

This sort of thing can probably be calculated, or you can do as I've done, and set up a test bed. In my case this is a beam with the 11th and 12th fret on it (the 11-12 distance doesn't vary much in the range of usable scales, so I didn't worry about it). The first fret is adjustable in position so that it can be set at the correct distance from the 12th, and the nut and saddle are also adjustable. There's a pickup in the saddle that can be plugged into a tuner. I set things up at the 'theoretical' measurements, and check the intonation at first and 12th frets. Then its a matter of making adjustments. I like to set the saddle up to get the 12th fret right first, and then check the first fret. Once that's properly adjusted, I find that the saddle is off (too far back), and adjust that. Then it's back to the first fret. After a few iterations I get to the point where it;s hard to make it any better, or I'm chasing my tail, so I note the offset measurements down, and go to the next string. It's a good idea to do each string two or three times, taking them off and re-mounting them to eliminate any systematic errors. Then I use the average of the offsets at either end. This, as I say, tends to get things 'pretty close'. It's a fair amount of work, but it's never easy to do things right.

[smurph1]

This whole compensated nut discussion is intriguing to me, but not enough for me to have one installed. If it's true that the improvement is not discernible to my ear then what's the point? My guitar plays and sounds fine, (to my 60 year old ears) so if it ain't broke, why fix it?

[Alan Carruth]

The idea of compensating nuts actually goes back a fairly long way. I've got an article from the '80s about it, for example. The problem is that most of the ones I saw until a few years ago were not too clear on what was going on, and I didn't understand them. Then Trevor came out with his book and, at about the same time, I attended a talk about it at a GAL convention, that clarified the whole thing.

I'm not sure anybody 'needs' a fully compensated nut and saddle. Then again, nobody 'needs' a guitar, either. Given the deficiencies of Equal Temperament you're never going to have something that sound as sweet as you might like. Still, in my experience, getting the intonation closer by doing the nut properly is worthwhile.

Several years ago I went to a folks festival with two guitars I'd built. When things got slack in the craft room I'd sit and play for a while. I soon noticed that I was picking one up far more often than the other, and playing it longer when I did. I had to think about it for a while, and realized that one had been out on loan. I'd just gotten it back and not had time to put on a compensated nut. That's the one I didn't enjoy playing as much. Yes, it's noticeable.