Time to crack that Nut

Signs of dissonance over Xmas

The open chords were not sounding as good I’d like

I’d been feeling something was not right about the nut on that acoustic for quite some time. In the past I’d tried to adjust it myself, with … “some improvement”, but the usual sweet spot of the acoustic guitar — chords near the nut — was not feeling so sweet.

Time to do some science — well measurements at least.

So, the previous nut may have been a little too high, and it’s possible the string slots were not cut (by me) so as to have the correct string length.

Net result? A pretty serious disagreement between the open strings and the pitches of notes when fretting lower frets.

Now this is the guitar where I had been on a journey to seek better intonation up the neck. I settled on 0.010 gauge in the end, which sounds fine and has the best intonation.

The bridges of Martin County

Tuning up the open strings and recording the frets I get this chart for deviations. On the right frets and strings, those numbers can make you feel a little queasy…

The effect varies by string as some of these wound strings are much stiffer than their siblings. The physical maladjustment of having too much travel to fret the notes will result in more or less degrees of going sharp.

How bad are these numbers? Absolute difference

To put it into context, the difference between an even tempered major third and a just tempered third is 14 cents (14% of a semitone) and this can be discerned by most audiences. The guitar is typically tuned to even tempered intervals and so raising the already sharp major third interval by the same amount is significant.

Equal temperament

How bad are these numbers? Relative difference

What is worse, as we can see is that the deviation varies wildly across strings, ensuring that not only can you not play sweetly in tune with any backing band, but any stand-alone chord on that instrument will sound equally out of tune with itself.

OK, Pretty bad: let’s install that bone nut I had lying around.

This nut seems to have just the right radius and slots for these strings. I only had to knock out the old nut, losing a few splinters of wood in the process and then to grind the nut down to the right height.

This process is very sensitive — less than a millimetre can turn your nut into a guide for your brand new zero fret (joke), so take it slow.

Here it is polished and installed- the strings lie in their slots nicely and at a very comfortable position,

Net result: captured from the most photogenic angle — note the action is a good size

So, let’s see if it makes a difference to the tuning.

Indeed it does — the deviation is smaller and much more consistent across all the strings, which will make chords ring all the sweeter.

With new nut installed

Conclusion

This is something anyone will access to a decent electronic tuner can check. The luthier work is pretty minimal, and there are many replacement nuts of all materials available online for a very reasonable cost. Remember, being in tune is priceless.