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Thread: Intonation Question

  1. #1

    Default Intonation Question

    Whenever I hear about intonation issues from other people, it seems like the problem gets worse moving up the fretboard and is more/most pronounced at the 12th fret or so.

    But my own experience is that when there are intonation issues, it is worst nearest to the nut and gets better moving up the fretboard.

    Are there two different issues going on here? Why are intonation problems sometimes worse moving away from the nut and sometimes worse moving towards the nut?

    Would it be oversimplified to say one is a setup problem and the other is a build quality issue?

  2. #2
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    Bad intonation is like cancer. You cannot say what is the one thing that causes cancer and how do you remedy it. You can be born with cancer, you can be exposed to materials, you can give yourself cancer with cigarettes or cell phones. And treating the cancer will depend on how you acquired it.

    Same thing with intonation. Several things can cause it and accordingly it will manifest itself differently and will need different solutions.

  3. #3
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    Ripock is right. You really can't generalize. However, It is quite easy to determine if the nut, the frets, and the saddle are all fitted correctly in relation to each other. It is just a matter of measurement and simple arithmetic, and is a good place to start if you've got a uke with intonation problems.

    John Colter

  4. #4
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    There is an over-simplified answer, though it's not always right.

    If the problem is worse near the nut, then most probably the nut slots are not deep enough.

    If the problem is worse as you approach the 12th fret (and gets better again above the 12th if you have enough frets) then the saddle peak is in the wrong place, usually needing to go back a different amount for each string if the uke sharpens up the neck.

  5. #5

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    Quote Originally Posted by ProfChris View Post
    There is an over-simplified answer, though it's not always right.

    If the problem is worse near the nut, then most probably the nut slots are not deep enough.

    If the problem is worse as you approach the 12th fret (and gets better again above the 12th if you have enough frets) then the saddle peak is in the wrong place, usually needing to go back a different amount for each string if the uke sharpens up the neck.
    Thanks for that. When you say the saddle peak needs to go back, I don't understand. Do you mean the bridge and saddle are poorly positioned or that the saddle needs to be raised/lowered, or is it something else?

  6. #6
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    I know this much, the measurement from the nut to the 12th fret has to be the same as from the 12th fret to the saddle. Electric guitar have saddles that can adjust intonation by height and forward back position, most acoustic instruments like a ukulele have a fixed bridge/saddle which cannot be adjusted but could be repositioned by prying it off and re-glueing it. Some have floating bridges that can easily be repositioned. My sold body bass ukes have a removable bridge/saddle that can only be adjusted up and down, but I'm having my luthier make a bridge that has forward and back adjustment.


    This is Michael Kohan in Los Angeles, Beverly West near the Beverly Center
    9 tenor cutaway ukes, 5 acoustic bass ukes, 10 solid body bass ukes, 13 mini electric bass guitars (Total: 37)

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  7. #7
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    Actually, in practice, the distance between the nut and the 12th fret, and between the 12th fret and saddle is not the same. In most ukulele there is between 1/16” to 1/8” compensation added to the distance from the 12th fret to the saddle. This helps minimize the tendency for the notes to go sharp as you move up the neck. I am pointing this out to prevent any panic on the part of anyone who actually measures these distances and discovers the difference. For example, assume a soprano scale length of 13.75”. Distance from nut edge to 12th fret should be 6.875”. Distance from 12th fret to saddle with 1/16” compensation should be 13.935”.
    Brad
    Bradford Donaldson
    Kekaha, HI and Cannon Beach OR
    bradfordj48@outlook.com

  8. #8
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    Kohan Mike said, "I know this much, the measurement from the nut to the 12th fret has to be the same as from the 12th fret to the saddle"

    now THAT'S an over simplification, right there. If that is how your uke is set up, it could be the cause of the problem.

    John Colter

    ps. see post immediately above.

  9. #9
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    Yes! If nut-12th and 12th-saddle are identical distances the intonation will definitely be out. These guys know.

    I've played ukes built by John Colter and he gets good intonation on them. I've not had the pleasure of playing one of Brad Donaldsons's, but I've heard enough about them to be certain that his are good too.

    Intonation on a ukulele (and any other fretted instrument) is never perfect, it can't be because equal temperament is a compromise. Getting the intonation good enough can be achieved quite simply though.

    Assuming the nut slots are at the right height (which they aren't on most cheaper ukuleles), the main work is at the saddle. The theoretical 50/50 split of string length at the 12th doesn't work when playing, because by pressing down a string you stretch it a little and thus make it sharper. To compensate for this, the saddle peak needs to be set a little further back than the nut-12th distance. Ideally, by a different amount for each string.

    If I'm making a soprano I know from experience that the G and A strings need the saddle set back around 1.5mm, the C string around 2.5mm, and the E somewhere in between. So I start with the front of my saddle 1mm further back, and then file the saddle back at each string location until the fretted note at the 12th is exactly an octave above the open note. I end up roughly at the measurements I gave above. Then I make everything nice and smooth.

    Slanting a saddle does the same thing less precisely, but doesn't work well for a ukulele because the saddle needs to come forward again for a re-entrant G string (though it works for low G).

    You can do this with a commercial instrument if the top of the saddle is wide enough, but you might end up lowering it slightly in the process because you are moving the peak to a lower portion of the saddle (assuming it has a rounded top).

    Just to make matter worse, this only gives you the best result for strings of the same diameter and density. So if you change string brands, your compensation to achieve better intonation will not be quite the same. This doesn't really matter too much on a uke because the strings are stretchy, and fretting pressure probably makes a greater difference. On a steel string guitar for a player who wants intonation as perfect as possible, this can be noticeable.

  10. #10
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    Quote Originally Posted by Bill1 View Post
    A lot of people do not understand how the fretboard has been designed.

    The set of frequencies it is designed to produce are part of a mathematical and physics system called a Temperament. There are lots of Temperaments. They all have histories and issues.

    The industry standard used to design and set-up your ukulele is called Equal Temperament. it has an in built "error" of around 2 cents for the Perfect Fifth interval and other intervals. it is like an average thing. It sets up your uke to be in the middle of a ballpark, then you use technique to fine tune dynamically as you play. Most people do it sub-consciously after month or so of playing without ever being taught about it.

    An interval is a ratio between two audio frequencies, the root and the played frequency. played frequency/root frequency = interval expressed as a ratio.

    So intervals are expressed as ratios. Some examples are: octave interval = 2:1, Perfect Fifth interval = 3:2 (1.5), Perfect 4th interval = 4:3. There are 12 intervals in the scales we use today, one for each chromatic note in a scale. The "perfect" set of intervals come from a certain temperament which may be one of the oldest temperaments dating from Pythagorus. They are all about sets of ratios, 12 ratios one for each note, some quite tricky with fractions of numbers like 32. The problem with this Temperament is that it is great in one key, but very troublesome if you want to change key. The frequency sets assigned to notes only work well for one key, when you change key you need to tweak the frequencies, like trying to twiddle the tuner knob half through a tune that has changed key for the bridge.

    On an instrument like a violin which has no frets, you can tune by ear using physics. There is a thing called a beat, when you play two frequencies at the same time and they are the right frequencies you hear beats, tuning to a perfect fifth is done by twiddling the violin tuner knob until the beats are not there. The beats go away when there is a perfect 3:2 ratio of frequencies, this is a function of how sinusoidal waves interact. It works great on violins and has been used for centuries.

    So many uke players do not realise that this will not work on a ukulele that has been designed and set up to the current industry standard. The fifth interval programmed into the Equal Temperament is 1.49, not 1.5. The fifth note in Equal temperament does not have a perfect fifth interval to the root note. The beats thing wont work unless you have the exact ratio of 1.5. An interval or ratio of 1.49 makes an audio frequency about 2 cents different to what you get if you use 1.5. So we keep getting this continual chatter from those who can tune in perfect fifths by ear, but they do not understand ukulele tuning, they always say there is an intonation error.

    They try to tune the G string by ear using the beats and wonder why it ends up about 2 cents off from the note on the C string at fret 7, which should be the same note. Once they get the G string "wrong" it messes up the tuning most noticeably past fret 7. And they spend a lot of time twiddling. This "error" will happen in every uke that has been set up to the industry standard. Instead if you want to use tuning by ear for your ukulele with the best results you need to tune direct to the A note on each string or tune to the string in unison interval not to the Perfect Fifth interval. Unison is an interval or ratio of 1:1, IE the same note.

    On top of that there are real intonation problems caused by poor quality manufacture and poor playing technique.

    The first fret space is right next to the nut, it is where the string is hardest to push down because it is so close to the nut. it is a very common place to get an intonation error. There is no magic cure. A good set-up will help a lot.

    As you get further along the neck, you are getting into tighter fret spacings. Another problem is string height is often highest around fret 12, so there is a lot more potential for bending the string unintentionally.

    What you need to realise is that you have to work on technique more to get the intonation as you move along the fret board towards the sound hole. One of the benefits of a well made uke and well set-up uke is that you need to rely less on technique and it is easier to play with good intonation as you move along the fretboard. Some custom ukes are expensive because the maker has spent a lot of doing stuff you never see to make them so much easier to play up the fretboard. But often a good set-up will work as well.

    Anyway, I suggest that you do not take my word for it or read wishy washy explanations in other posts. Do some research into these headings: Temperament. Harmonic Musical Series. Rule of 18 (a model for fretboard design). Tables showing Equal Temperament frequencies. Tables showing the 12 ratios and names for each Temperament. Tuning a violin by ear.
    That is all so theoretical Bill1, we most know the errors between some pure harmonic scale by like a violin player and our instrument's notes. No need for such a long post, but I thank you for paragraphs, so I could read easy

    What we need to fix on our ukes is not to have too high nut action or wrong, first and foremost. And if the bridge bone is badly situated or in action that too. Some compensations can be done.

    After that our electrical tuner comes in working. I usually though think it is best to use mostly for open strings, if the nut action is fixed and not some improperly put frets to the depart from equal temperament. I don't want to make a compromise like make the fretted 12th string sound more in tune if the bridge bone is not in right place, too much.

    It is best to get the lower frets working as right as possible.

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