Intonation HELL! [Please Help]

Discussion in 'Hardware, Setup & Repair [BG]' started by kyral210, Feb 17, 2020.

  1. kyral210


    Sep 14, 2007
    I have a long scale 5 string with weird intonation.

    From the nut to the 12th fret is 44.5cm. I set my A string to be 44.5cm from the bridge, with all other strings up/ down from this based on string length. I tune up, use a strobe tuner, and can get perfect 12th string harmonics. All the saddles look right.

    But when I fret the 12th fret, I am sharp. Moving the saddles 1cm backwards solves this. My low B saddle is so far back I can hardly fit it into its slot.

    Is this right?

    Should I stay with the theoretically right placement that intones to harmonic, or drop back and intone to fret?
    Last edited: Feb 17, 2020
  2. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Drop back and intonate to fret. The reason is because your strings no longer form a straight line from nut to bridge the second you fret a note, and intonation setting is all about making up for it.
  3. JKos

    JKos Supporting Member

    Oct 26, 2010
    Torrance, CA
    Of course. The harmonic will always be in tune. That has nothing to do with adjusting the bridge.
    Setting intonation is all about the fretted note.

    - John
    DiscoRiceJ likes this.
  4. bholder

    bholder Affable Sociopath Supporting Member

    Sep 2, 2001
    Vestal, NY
    Received a gift from Sire* (see sig)
    Ah-yup, what they said.
  5. Yessir, intimate to the fretted note. Unless the string is bad the open note and the 12th fret harmonic should always be in tune with each other. Setting witness points, if you haven’t already, could help out the B string intonation. Well, all the strings, actually.


    Witness Points: The Pictorial
    Zooberwerx likes this.
  6. kyral210


    Sep 14, 2007
    So why is the intonation radically different to the theoretical scale length?
  7. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Yamaha, Ampeg, Line 6, EMG
    Theoretical scale length only matters when all conditions are perfect, and they never are. Strings are different sizes with different size wires. The strings get bent from perfection every time you fret a note. Your touch may be different than somebody else's, and what's perfect intonation for you could be a little off for someone else. So throw that theory crap right out the window, and move the saddles where they need to be so you play in tune with the harmonic when you play a note. That's the entire reason why they have adjustment screws.
  8. kyral210


    Sep 14, 2007
  9. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    Your harmonic 12th should match your 12th fretted. It's a fairly standard practice although not perfect. As @Matt Liebenau addressed in #5: did you set your witness points?

  10. kyral210


    Sep 14, 2007
    I’ve put the intonation back to fretted; so it’s now ‘perfect’
  11. ixlramp


    Jan 25, 2005
    I assume you mean 'I set my A string saddle to be 44.5cm from the 12th fret'?
    That is not how you intonate a bass guitar. To be intonated, all saddles will be behind the point that is 'scale length' from the nut. The highest string will be slightly behind, the thicker strings will be further behind.
    The theoretical saddle position at 'scale length' from the nut is only for a 'perfect string' with no stiffness and is not pressed down against the frets.
    Stiffness raises pitch. As you play higher frets the string becomes shorter and therefore stiffer, raising pitch, so the saddles must be moved back to compensate.
    Fretting a note stretches a string and therefore raises pitch. A string is pressed down by a larger distance on higher frets. So again the higher frets are increasingly sharpened.
  12. mech

    mech In Memoriam

    Jun 20, 2008
    Meridian, MS, USA
    When a string is fretted not only is the length changed but more importantly the tension is changed. It's being stretched and goes sharp. Half scale string length from 12th to saddle must be increased over the measured half scale length to compensate and set the intonation. The amount will depend mainly on the strings gauge and construction. Neck stiffness and amount of force used to press the string down are also in the equation. Witness points must always be properly set as already mentioned.
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    Primary TB Assistant

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