What aspect of a uke's construction controls how well the intonation is?

eclecticbanjo

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I have some cheap Luna ukuleles I bought for Xmas for my girls which have horrible intonation when compared the open notes with their 12th fret octaves. I then had a chance to play some more expensive ukes the other day and found that their intonations were spot on. So it got me wondering what the difference between them were? If both a cheap uke and an expensive uke have similar scale lengths and size, what is it that makes a ukulele have better intonation?
 
Compensation, proper saddle placement, fret height, action, strings. That's all I got right now.
 
Several things.

Measurement from nut to 12th fret determines the scale, 12th fret to bridge should be the same or your open strings will be off. The open string should match the 12th fret note.

On better ukes the saddle is slightly angled farther back from treble to bass side, to approximately compensate for the string thickness effect on pitch. There are ukes where the frets are also angled the same as the saddle.

On some ukes a compensated saddle is shaped for the length of each string, which is technically more accurate, especially with a high G. There are also compensated nuts. You can even have slightly zig-zag looking compensated frets, but that is very rare.

Spacing of frets has to be specific percentages of the scale or individual notes will be off. Fret height, too high will make notes sharp.

In actual practice, these measurements aren't perfect. Some would make others less perfect, so most measurements are a compromise. The trick is to divide the compromises so that each is only an imperceptable amount.
 
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I have some cheap Luna ukuleles I bought for Xmas for my girls which have horrible intonation when compared the open notes with their 12th fret octaves. I then had a chance to play some more expensive ukes the other day and found that their intonations were spot on. So it got me wondering what the difference between them were? If both a cheap uke and an expensive uke have similar scale lengths and size, what is it that makes a ukulele have better intonation?
In my experience, cheap ukes usually have reasonably accurate fret boards - as regards the fret spacings - but the string height (over the frets) is usually way too much. This means the player has to press down with too much force, stretching the strings out of tune. Also the placement of the nut, relative to the first fret, is often very approximate, the bridge position can be just plain wrong and the original strings may be woefully poor.

Someone with experience of setting up a uke can usually make very useful improvements. Some cheap ukes, though initially disappointing, can be transformed into really pleasing instruments. I have several cheapies which I really enjoy playing - they all needed fettling. Fortunately, as a hobby builder, I have the tools and the experience necessary.

ps. not all of my cheapies needed to be adjusted: I bought two very inexpensive Aiersi HPL pineapple sopranos, both of which were perfectly set up, right out of the box and they still have the original strings fitted. That is unusual, to say the least!
 
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Temperature and humidity matter. I've messed around with 2 $100 ukes and a Martin Uke. All 3 have shown me good intonation on different days and bad intonation and others. The one that stays in my car most of the time actually seems the best when I've tested it.

For beginners, unless it's awful, I don't think the intonation matters that much because mostly I play at the top of the neck and rarely play anything beyond the 5th fret. As skills and range get better it will matter more.
 
FWIW, compensated guitar frets. Weird. I think some people are way too obsessed with perfection. I don't lose sleep over a note being few cents off. "Perfect" ain't gonna happen. Maybe with a digital uke that has 68 buttons instead of strings.

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In my experience, cheap ukes usually have reasonably accurate fret boards - as regards the fret spacings - but the string height (over the frets) is usually way too much. This means the player has to press down with too much force, stretching the strings out of tune. Also the placement of the nut, relative to the first fret, is often very approximate, the bridge position can be just plain wrong and the original strings may be woefully poor.

Someone with experience of setting up a uke can usually make very useful improvements. Some cheap ukes, though initially disappointing, can be transformed into really pleasing instruments. I have several cheapies which I really enjoy playing - they all needed fettling. Fortunately, as a hobby builder, I have the tools and the experience necessary.

ps. not all of my cheapies needed to be adjusted: I bought two very inexpensive Aiersi HPL pineapple sopranos, both of which were perfectly set up, right out of the box and they still have the original strings fitted. That is unusual, to say the least!
Well said as to action, John.

Example to further explain for the benefit of the OP: The curve- shaped plastic bridge that came with Yowling Tom’s cheapie kit is a bit too tall. When coupled with the design flaw of a neck joint surface that was improperly angled to the extent that the bottom of a metal straightedge laid flat across the soundboard is 2mm lower at the nut than at the 12th fret, it’s impossible to sand off a sufficient portion of the saddle to lower action below 3.5mm.

I’ve literally sanded my bison bone saddle down to the point that it would be flush with the top of the saddle slot if I sanded any more, but 12th fret action remains at 3.5mm.

Thus, my next planned mod is to replace that original bridge with a far tidier Grellier-spec rectangular bridge. For the simple reason that the bottom of the saddle slot will then be nearer the soundboard, I expect that change to enable me to bring the action down to where it needs to be.
 
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One of the ones I played at the store that had amazing intonation was a Martin S1 that went up to 17 frets, had a compensated saddle, might’ve had a neck with adjustable action, but all together was just a vastly superior instrument. I’ve been playing clawhammer style on my girls ukuleles and am starting to see the chasm between theirs and a good uke.

Are other brands/models of particular excellent intonation like the Martin S1? I liked it but can’t imagine spending $400 on something that I don’t necessarily like how it looks.
 
The worst intonation can be gotten by placing the frets in the wrong places. I've heard that fan fretting can produce improved intonation.
 
Check out reviews at gotaukulele.com in different price ranges. The ones that get Baz’s recommendations always have solid intonation, and he reviews them in all price ranges (he’s in the UK, but many of the ones he reviews are available in the US).

What about the Martin’s looks were unappealing?
 
didn’t care for the pinstripe around the sound hole compared to the rest of the Uke, the finish on the mahogany felt kind of Ho hum, wanted inlay markings on the 3rd and 12th frets, things like that.

I did like the friction tuners, the 17 frets, the simplicity of design, the solid wood, and the sound was absolutely amazing, so ya know, may still pursue one one day.
 
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If it may help : I saved a very cheap Kmise with a very slight intonation problem on the E string, simply by stucking a very tiny bit of wood match under the string, the closest possible to the nut groove. The instrument now intonates perfectly.
Hope this helps,
regards.
 
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