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Adjustable Intonation Nut


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After all, the first fret is no higher than the second, the second is no higher than the third etc.

That's incorrect. Although, all frets have exactly the same height, a string fretted on 1st is higher than open (assuming the zero fret) a string, fretted on 12th is significantly higher at 13th -- just straight geometry.

That is not incorrect. All the frets are the same height (as you agree), therefore the first fret is no higher than the second fret, the second is no higher than the third, etc. The string angle changes slightly on each fret, but I was talking about frets, not strings.

the "zero fret", or a nut adjusted exactly to the fret height, will tend to interfere with the 1st fret when you play hard

Sorry, I disagree :D

In a perfect world, the best setup would be parallel, with the strings about 1.2mm above every fret, like this:

_____________________________

. . . . . . . . . . . . . . . . . . . .

Unfortunately, the world isn't perfect, and it would be murder trying to hold the string down behind the first fret, and of course, the fret spacings would have to be altered :D

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Sorry, I disagree :D

In a perfect world, the best setup would be parallel, with the strings about 1.2mm above every fret, like this:

_____________________________

. . . . . . . . . . . . . . . . . . . .

Unfortunately, the world isn't perfect, and it would be murder trying to hold the string down behind the first fret, and of course, the fret spacings would have to be altered :D

I'm sorry for being annoying, but I can easily prove a theoretical necessity of a compensated nut even with the zero fret. Straight physics and geometry.

Firstly, no way! A parallel fret board wouldn't work at all.

fretboard01.jpg

It would simply prevent the strings from vibrating (the sizes on picture are exaggerated for clarity). The amplitude of the fundamental frequency in the middle may easily be more than 1.2 mm. Then, about the geometry. If you remember the Pifagor theorem, you сan easily calculate the change of the length when fretting. Suppose, your string deflection is 1 mm along the whole fret board. Taking more or less realistic sizes, you add about 0.0005% to the string length, when you push the string in the middle. But with the same deflection distance at the 1st fret, you add about 0.005% - ten times more! That's why it's so hard to play with a high nut (not to mention bad tune), while in the middle you easily push the strings. So, the slope fretboard is essential! Then, if you calculate the extra length with a slope fretboard (assuming your favorite 0 fret), you will figure out, that from 1st to 12th frets you add almost exactly the same extra length and so, extra tense!

Then, since you inevitably add tension along the entire fretboard, you want to compensate it. So, you adjust the bridge intonation. But! The bridge intonation almost DOES NOT affect the low frets! Just because the relative difference of the length is small (with and without saddle compensation). And, since different strings have different characteristics "delta-tense" to tune, the slot positions at the nut must be different. So, it proves at least a theoretical necessity of having a compensated nut. Although, the zero fret improves the tune, it's still theoretically necessary to compensate. I say, "at least theoretically", because I'm not really sure if there's any significant effect in practice. Probably not, otherwise a compensated nut would be already popular, as the saddles with intonation are.

McSeem

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The amplitude of the fundamental frequency in the middle may easily be more than 1.2 mm

That's strange, because I have a guitar (and have seen many many more) with the string action set at 2mm high at the 24th fret (10-46 string gauges), which means the height above the 12th fret is just 1mm (actually up to 1.1 allowing for neck relief), and playing open strings does not cause them to hit the 12th fret.

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That's strange, because I have a guitar (and have seen many many more) with the string action set at 2mm high at the 24th fret (10-46 string gauges), which means the height above the 12th fret is just 1mm (actually up to 1.1 allowing for neck relief), and playing open strings does not cause them to hit the 12th fret.

Of course, it can be even 0.5 mm, and it will sound well, but you can't play hard. A typical recommendation is 2.5-3mm at 12th. I also set it lower, about 2mm. I was talking about the difference between a parallel fret board and sloped. Well, actually, the system is kind of self-regulating. When the string hits the frets, it restricts its amplitude, but still it's undesirable. If it happens at the very attack moment, it's OK (slapping), but it may happen later. The thing is the string vibration is polarized. Initially, the polarization is about parallel to the frets, which theoretically allows you to have a very low string setup. But the polarization is rotating. And when it gets perpendicular, the string may easily interfere with the frets. I'm sure you heard that -- you pluck the string, and after a while (1 second or so) it starts buzzing.

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So that I came up with an idea of fully adjustable nut. It's not about the height, it's only about the position. I have a couple of versions of the design in my mind, and my main question is: in your opinion, how cool would it be to have this kind of a nut? Is it worth giving a try, or it doesn't make much sense?

McSeem

I think this is a sorely needed feature in guitar design. It makes no sense to not to have an adjustable nut when it's standard practice to have adjustable bridge saddles - at least on electrics.

Please keep us updated on your designs and feel free to correspond with me about it. I will be developing individual adjustable nut saddles for my multi-scale guitar designs.

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Microfrets guitars in the 60's had adjustable nuts. Each string had it's own nut and was adjustable. Not only for intonation but height as well. Ask me how I know this? I owned one. I bought one in 1968 brand new. It was also one of the first using a Fiberglass/foam core body, and was much less weight than my strat at the time. :D

MK

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Ah...micro frets was the guitar I was thinking off I think...but I am sure tehre have been other attempts at this kind of thing on some older obscure guitars...

...

Doing a project at the moment and also a solo project (so won't be playing with other guitars too often) and being very picky about tuning and intonation...have been doing a bit or research today...

Earvana certainly seem to have a good practical product for a wide range of instruments...

I was looking at something that was friction reducing or even a roller nut or LSR...they make a non-slippery, LSR conversion nut would you believe!!! But nothing that would work great with a tremelo...perhaps they should make an LSR version with adjustable intonation since the fretboard already needs modification and the nut is screwed in and height adjustable.

Oh well...was a long shot...but did get this quote from their site of a magazine review...

To our ears, the Earvana nut went a long way toward solving most intonation problems, especially those found in the first, second, and third positions. Also, chords played all over the neck seemed sweeter and more piano-like. However, we found this improvement came at the expense of unisons involving fretted notes and open strings. Guitars can never be intonated perfectly, but the Earvana nut provides a marked improvement over the status quo.

I'm not sure if this would apply to the buzz frietlin system as well, perhaps not as they have elaborate tuning offsets as well...but this would be a huge disadvantage to the way I often play, especially this "solo stuff". I will often use fretted and open strings often fretting way up the neck to get harp like efffects alternating with opens...and harmonics as well within chords and melody lines that alternate between fretted and open notes...

However, while there is always some intonation issues in the nature of the guitar, it is amazing how a really well set up conventional guitar can play extremely "in tune" and I'd have to seriously reconsider doing something like this to an instrument if there are down sides with open strings and fretted notes not in the open position 'cowboy chord' style that these things are perhaps anticipating sounding "better with it"...perhaps there is something more I am missing...but along with this possibility, just a height adjustable nut itself would make setting things up so much easier regardless of intonation features...and perhaps something a little more 'slippery' than typical nut material.

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