Effect of lowering the saddle on intonation.

My first uke was the worst I bought, and I now finally found some time to try to 'fix' it in April.
I'm going to lower the action, and was wondering what the effects would be on the intonation before I go to work.
I have to lower the nut, that's for sure. The least I want to get out of it is a uke for my kid to strum basic chords 'nut-side'. I'm also thinking about sanding down the saddle, as the action is quite high at the 10+ frets to.
Question: Aftering the nut to my desired heigth, will sanding down the saddle effect intonation?

The reason high action impacts intonation is that the string needs to be deformed more to reach the fret. This deformation pulls the tone high. It is easy enough to adjust the saddle as well if you're comfortable adjusting the nut and can only help (as long as you don't drop the action too low). If your kids are only going to be noodling around on the first few frets it doesn't matter too much. You should also put a straight edge across the frets (between the strings) before you start anything to make sure they are level. A high fret could create buzz if you lower the nut.

Thanks. I was asking because I was (and still am) wondering if the slight difference in string length after adjusting the saddle has influence on the intonation. I guess I'm also wondering what factors DO have an influence on intonation.

Ukuleleblues said:

You might find this interesting reading on your quest for better intonation.

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Wonder why they used an example with the action being 10mm at the 12th fret...??? Holy mackerel, that would be a lap steel setup for slide playing...!!!

Lowering the nut slots greatly improves intonation at the first couple of frets (if the slots were too high, of course).

The bridge saddle height has far less impact on intonation - I've lowered actions to 1/3rd their original height at the twelfth fret (going from just ridiculously high to a little lower than most people seem to like) and it didn't make more than maybe one-cent difference on any of the strings.

A simple look at the geometry explains why - when you fret the string at the first couple of frets that is very, very close to the nut. If the nut is high then the string has to stretch a lot. At the other end of the fretboard, there are several inches between the last fret and the bridge saddle. So, even when you fret up high the string has to stretch much less even though the gap being closed is larger.

So, the bottom line is to adjust the nut for perfect intonation at the first couple of frets and then adjust the saddle so barre chords up the neck are comfortable, but don't sweat over getting super low action at the bridge end unless you just like it that way. If you can't get the action as low as you want without string buzzing, and don't want to go to all the trouble of leveling frets, then sacrifice the action at the bridge end because it has far less impact on intonation.

John

WhenDogsSing said:

Wonder why they used an example with the action being 10mm at the 12th fret...??? Holy mackerel, that would be a lap steel setup for slide playing...!!!

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Yeah, that's pretty high. My full-size, five-string bass is about 2.5mm on the bass side at the 12th! Actually, it might be a little lower than that since I put the flatwounds on it.

John

ukuhippo said:

...I was (and still am) wondering if the slight difference in string length after adjusting the saddle has influence...

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Lowering the saddle (won't exactly change the string length, btw) will cause the notes up the fingerboard to be just slightly flatter than they currently are, which is probably good because if the action is already too high then I am guessing the higher notes are probably too sharp anyway. Try playing a single harmonic over the 12th fret, then play the same note fretting the string; do the notes match? Is the fretted note sharper?
Same goes for the nut, especially the first couple frets will be noticeably sharp when the action is too high at the nut.

Thanks a lot guys, much appreciated.

OldePhart said:

Yeah, that's pretty high. My full-size, five-string bass is about 2.5mm on the bass side at the 12th! Actually, it might be a little lower than that since I put the flatwounds on it.

John

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What is the "ideal" low action height at the 1st and 12th frets for a tenor uke? And is that from the fretboard or crown of the fret wire? Thanks.

uke2020 said:

What is the "ideal" low action height at the 1st and 12th frets for a tenor uke? And is that from the fretboard or crown of the fret wire? Thanks.

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I like to have the strings about 0.010" above the crown of the first fret. I use a set of automotive feeler gauges when filing the nut slots. The lower you get them to the crown of the fret, the more chances you'll have for buzzes. I consider the action at the nut to be satisfactory if I can easily barr all first strings on the first fret with my index finger. Hope this helps.

uke2020 said:

What is the "ideal" low action height at the 1st and 12th frets for a tenor uke? And is that from the fretboard or crown of the fret wire? Thanks.

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Ideal varies from person to person. I tend to like lower actions then a lot of people. For the bridge end, if it's low enough that it doesn't have much impact on intonation and if you're comfortable playing with it then it's "ideal" for you. The nut end needs to be low enough that the strings don't pull sharp at the first fret.

John