Inntonation: How do you know?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by emjee, Mar 17, 2005.


  1. emjee

    emjee Member

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    I am sorry for askin such a basic question, but I dont know anything about set-up, intonation, stuff like that. How are you supposed to know if the intonation is right? I was told about 10 years ago
    that you hit the 12th fret harmonic, and then hit the fretted 12th fret, and if they are the same then they are intonated. Then I have heard thats not right. Is a tuner required? I just know it involves making the saddle move forward or backward, to adjust the length of the two points where the string sits. Any input appreciated.

    Thanks,
    Matt
    San Rafael, Ca
     
  2. angelo

    angelo Member

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    I started out with the 12th harmonic thing too ....


    But a long time ago, I started listening to the people who know a lot more than me.

    Open string in tune
    12th fret fretted in tune


    I believe that has made a difference in my guitars being tuned correctly.
     
  3. emjee

    emjee Member

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    Hey thanks! Also, is there a way to get every note you play to have an equal amount of sustain? I'll hit the third sting ninth fret
    lasts for three, maybe four seconds, while the second string at the same fret lasts up to seven or eight seconds. And other
    notes vary in seconds from place to place around the fretboard.
    Has anyone ever owned a guitar that sustains the same duration everywhere around the fretboard?

    Thanks,

    Matt
    San Rafael, Ca
     
  4. John Phillips

    John Phillips Member

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    That will give exactly the same results - the 12th fret harmonic is always an octave above the open string, so from an intonation point of view it's the same note. It's actually easier to use the harmonic, because it's the same pitch as the fretted note.


    IMO there's a much better method.

    First, tune each pair of strings (1/2, 3/4, 5/6) perfectly using the 5th/7th fret harmonic method - yes, I know this isn't correct for even-tempered tuning, you're just setting each string as a reference for the other for now.

    Then, play a harmonic on one string and compare it to the same fretted note on the other. This is far more accurate because both notes are ringing at the same time, so you can hear precisely if they are in tune - and if not, even hear how much they are out by, from the 'beat' frequency between the two. You need the 12th fret harmonic on the higher string vs. the 17th fret note on the lower one to set the lower one, and the 19th fret harmonic on the lower string vs. the 14th fret note on the higher one to set the high one.

    You don't need 'golden ears' to do this - it's easily audible.

    This is quite normal - guitars are made of wood (usually), which isn't a consistent material and has all sorts of variances and resonances, even within the same piece. The design of the guitar (especialy the neck join) makes a difference too. It's rare to find one where all the notes sound and sustain exactly the same. Some are so bad that there are 'dead spots' where certain notes either don't sound right or die quickly.

    My PRS Standard is one of the most even guitars I know of, but that's just luck. My Custom is less so, although it doesn't have any dead spots - which are surprisingly common on some models, around the 12th fret on the G string on the 24-fret ones in particular.

    There's not a lot you can do about it, usually - although changing the setup and/or string gauge can sometimes help.
     
  5. The_Whale

    The_Whale Member

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    If you have a tuner, you don't need to use harmonics, and there is nothing special about the 12th fret.

    You need to remember that intonation is a compromise: It isn't really possible to get every fret perfectly in pitch.

    The trick is to make your guitar sound as good as you can for the style you play.

    Here is how I check/set the intonation on my guitars.

    First put on new strings and tune them (with a tuner), play the guitar for a while to make sure the strings are stretched properly.

    Tune the strings to pitch. Fret a B chord at the 7th fret; as you fret the six strings, check the pitch of each string. (are any sharp or flat?).

    If any of the strings are sharp or flat, adjust the intonation for that string.

    Tune open strings to pitch. Fret B chord at 7th fret; as you fret the chord, check the pitch of each string.

    If any of the strings are sharp or flat, adjust the intonation for that string.

    repeat until the open strings are in tune, and the six notes of the fretted B chord are in tune.

    I use the 7th fret, but any just about any fret between the third and the 15th is "doable".

    any questions?
     
  6. emjee

    emjee Member

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    Many thanks, all you guys, I appreciate the info. It gives me a choice
    of methods, and I can pick which works best for me. On a gibson type bridge, if you have to turn those inntonation screws, how do you get a screwdriver into such a tiny space (That is, between the tailpiece and the bridge)? How do you know which way
    to turn them? Also in what circumstances would I need to shorten or lengthen the distance between the nut and the saddle? Again you guys, thanks for the help. Also, I have the buzz feiten tuning system.

    Matt
     
  7. The_Whale

    The_Whale Member

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    You need to use a very small screwdriver, and you need to really slacken the string.




    Think about it: if the fretted note is sharp, you need to "flatten" it. You "flatten" the note by increasing the distance between the fret and the saddle (by moving the saddle away from the nut).

    If the fretted note is flat, you need to "sharpen" it. This is done by decreasing the distance between the fret and the saddle. (by moving the saddle towards the nut)

    You can figure out for yourself which way to turn the screws: loosen a string to slack, turn the intonation adjustment screw clockwise and take notice of which direction the saddle travels (does it more towards the nut, or does it move away from the nut?)

    You got it?


    I am not familiar with the particulars of that tuning system, but I don't think that makes any difference when setting the intonation.
     
  8. spaceboy

    spaceboy Member

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    what would it mean if your 12 fret harmonic was out of tune with the open string? which, i realise, is theoretically impossible yeh? but i'm sure i've seen it on my strat... old strings? inconsistent tuner?
     
  9. Brion

    Brion Supporting Member

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    Your pickups may be too close to the strings causing a magnetic interference.
     
  10. spaceboy

    spaceboy Member

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    hmm, after further investigation this calls for a new thread!
     
  11. angelo

    angelo Member

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    I understand the theory that 12th harmonic equals the open string.

    Nonetheless, as a tinkerer, I have always done my own set ups. And, to my ear, my setups have been much better across the entire neck when I started comparing the open to the 12th fret rather than the harmonic to the 12th fret.

    Just IMHO:)
     
  12. aquadog

    aquadog Member

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    I've found this to be true as well. I'm sure a tuners probably more accurate, but for some reason, I just get the feeling I'd screw things up worse if I tried to do it differently.
     
  13. emjee

    emjee Member

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    Thank you for the help and information. It was easy to understand the way you put it.
     
  14. Rob DiStefano

    Rob DiStefano Member

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    I'd would never intonate a string using harmonics.

    Guitars are deflected string instruments with precise interval "stops". Since the string is deflected to all stops, the fretted string will always play sharp. This is why I intonate an open string to it's fretted 12 fret stop. And this is why a change in action will affect intonation.
     

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