Bridge/Nut String Spacing and Intonation

[Christian Wadlington]

Aloha Builders,

I am in the middle of a build and have a question about string spacing. I see that it is very common to have a wider spacing at the bridge and narrower at the nut. My question is, wouldn't this create longer strings at the outside and narrower at the middle? Wouldn't that in turn create an out of tune chord when pressing down the bar and playing across the strings? Or maybe there is some compensation in the height of the strings in the bridge/nut or some other magic I am unaware of. Or maybe miraculously this doesn't really matter to the ears (although I bet it would to some). Admittedly I have not done extensive research on this, but after 30 mins of searching I haven't found an answer and hence this post.

Mahalo for your kokua!!

[Andy DePaule]

Hi Christian,
Yes but it so little extra width that it makes no difference. Remember we are not glued to the frets like a standard guitar and they have the same issue.

When we play steel the frets are just places to aim for with our eyes and our ears tell us when we are there. Even if the frets are not in the perfect place we'd still play much the same.

Some steels have less width difference between the nut and bridge and others have almost parallel strings. Parallel strings are not for that reason, but to make bar slants easier in the lower fret positions.

More important is string length. Longer scales 24&1/2" to 25&1/4" make harmonics easier to get. The shorter scales around 22.5" make bar slants easier.
For pedal steels 24" to 24&1/4" are kind of a standard with a few exceptions, but that is to help prevent string breakage with all the string stretching from the pedals and knee levers.

I prefer the shorter scales length because I'm not very good with harmonics anyway and do better with slants. There is no hard rule because it's just a matter of the players preference.
Good luck with the build,
Andy

[Christian Wadlington]

Thanks Andy, I suspected as much. Just making sure I am not making some grievous error as I am a builder newbie. Mahalo sir!

[Ian Worley]

As Andy said, the difference in scale length is much to small to be of concern. On a typical 24" scale 10 string guitar w/ ~11/32" string spacing at the bridge and ~19/64" at the nut, the difference in scale length between the two shortest inner strings and the two longest outer strings is less than 1/1000". 24.00000824 - 24.00066734 = 0.0006591".

That would amount to ~0.06 cents tuning difference at the 7th fret, but more important to note that the ratios between frets, nut and bridge remain constant regardless of the relative angle of the string. On a steel guitar with fixed parallel bridge and nut, each string has a very slightly different scale length, but ratios for a bar placed above a given fret and parallel to the bridge/nut/frets are constant.

[Ian Rae]

Ian is right - the geometry of similar triangles takes care of the tuning.

As far as I can see, the only reason for tapering towards the nut is aesthetic, but it's a nice aesthetic - I did it when I built mine

[Dave Mudgett]

I agree with everything stated - the differences in scale length are too small to hear, the similar triangle argument stating that the ratio of string length in front and behind the bar doesn't change is correct, not to mention the fact that bar placement overrides every other single issue except perhaps serious errors in open string tuning.

And add to that the fact that the model on which all these string tension vs. scale length vs. pitch calculations are made uses a very idealized model of a string which is not realized in practice. One issue is that strings have stiffness which varies from string to string. So there is a distance from the takeoff point at the nut and bridge where vibration is not free, which reduces the effective scale length of the string, and that varies from string to string. This is part (but not all) of what causes fretted guitars to need variable lengths of compensation for different strings. With fretted guitar, there is also the vertical string deflection caused by fretting the string. And no doubt other second and/or third-order effects.

If one was to worry about this stuff, one would go nuts trying to play. Playing in tune must be handled by hand/eye/ear coordination and an experiential understanding of where there may be slight tuning issues on the guitar. That is my belief, anyway.

[Jeff Highland]

It's basically a remnant of the origins of Steel guitar coming from the Spanish (fretted) guitar where left hand comfort and ergonomics were better with a narrower nut, but the plucking hand was better with a wider string spacing.

A taper just tends to look right to the eye when we are used to seeing it.

Makes NO difference to intonation.

My Duesenberg has equal spacing

[Les Ford]

Here is a related discussion with Paul Franklin and Buddy Emmons where Buddy comes up with some interesting ideas about angles and spacing as well as some fascinating history of the instrument.

https://bb.steelguitarforum.com/viewtop ... highlight=

[Andy DePaule]

Hay you guys are making me feel bad. I flunked out of geometry and algebra was another story, with that it was not the answer that was hard for me, it was what the question was!

I'm not kidding, Been building guitars since 1969 and use geometry to get that done all the time, but I have no idea how to do the math involved.
It was always my worst subject. I did good in art & shop class.
I also always liked history because I'm a dreamer and could imagine myself in those times and places.

[Ian Rae]

But Andy, if you were great at mathematics would you be any happier in your life? It's useful sometimes but I don't find that it raises the spirits all that much

[Andy DePaule]

Hi Ian,
Doubt I'd be better off if I could do those things.
Been self employed most of my life and as long as I can add, subtract, multiply and divide that's all I've ever really needed.
More important is that I can ball park those 4 in my head and usually get close enough.

My worst sin is that as much as I the actually hate doing math is that I alway put it off too long and then have to spend days catching up for taxes.
This year I've been doing month end totals with YTD so maybe I can get it down to a few hours at the end of this year.

[Jim Pitman]

When I put together a lap steel I made the nut and bridge string spacing the same. Bar slants are more forgiving - one less variable related to the position up and down the neck.