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Scale length and intonation

Discussion in 'Hardware, Setup & Repair [BG]' started by subdude67, May 17, 2019.


  1. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    I am putting together a parts bass.

    The neck is a 34 scale and I placed the bridge with the saddles in the middle position to 34 1/4 from the nut. All 4 strings are sharp by quite a margin. When I adjust the saddles accordingly the scale length is almost exactly 35 inches.

    It is not a problem, I got it all set properly but I am wondering how that is possible?
     
  2. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    Measuring from the nut to the 12th fret should give a solid answer.
    My 30" scale neck is 15" to the 12th fret.
    Is yours 17", or 17.5"?
     
    Last edited: May 17, 2019
  3. How or what did you measure? From the nut or 12th fret to the position of the saddles or to some other part of the bridge? FWIW when I position a bass bridge I usually measure from the nut to the G saddle set probably 80% forward (towards the neck) in its travel.
     
    mech likes this.
  4. SteveCS

    SteveCS

    Nov 19, 2014
    Hampshire, UK
    @Matt Liebenau beat me to it, but...

    1. Measure nut (inner edge) to middle of 12th fret.
    2. Set G saddle to about 80% forward position on the bridge.
    3. Place bridge with G saddle positioned the same distance from 12 as measured in 1 above.
     
  5. LetItGrowTone

    LetItGrowTone

    Apr 2, 2019
    If it's 35" with intonation set properly as he said, then he accidentally received/used a 35" scale neck. That's what I meant. Just measure from nut to 12th fret to check.
     
    Last edited: May 17, 2019
  6. Bruce Johnson

    Bruce Johnson Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    If the scale length of the neck is 34", measuring 17" from the nut to the 12th, then after setting the intonation the final distance from the nut to the fulcrum edge on the bridge saddle will measure about 34 1/8" on the G, out to about 34 3/8" on the E.
     
    mech and /\/\3phist0 like this.
  7. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    Thanks for all the replies:thumbsup:

    The neck is without a doubt from a 34 scale bass. I measured 17 iches from the 12th fret to the witness point of the saddles. In the end I hat to pull all 4 saddles back to the max in order to get in intonated properly making the scale length 34 3/4 inch. And I thought that is remarkable but maybe not, I never measured the scale on a bass:D
     
  8. An extra 3/4” to intonate seems like a lot but it could be. Forgot to mention, did you set witness points before you checked the intonation?
     
    Zooberwerx likes this.
  9. Have you checked the intonation at other frets such as the 3rd and 7th?
     
  10. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    yeah, but did you measure from the leading edge of the nut to the 12th fret?
     
    mech, SlingBlader and /\/\3phist0 like this.
  11. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    Yes I did, nut to 12th fret is 17 inches, 12th fret to saddle was also 17 inches. Intonated it is now 4mm shy of 18 inches from the 12th fret
     
  12. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    hmm.

    how straight is the neck and how high is the action? are the witness points at nut and saddle straightened out?

    high action and leftover curving at nut and saddle will both push intonation sharp.
     
  13. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    The neck is very straight and the action is as low as I could get it. And again, the bass plays good and the intonation is right so there is not really any problem, I was curious what caused the scale length to increase, that's all
     
  14. ixlramp

    ixlramp

    Jan 25, 2005
    UK
    I've written elsewhere about this but, to set intonation carefully, do not use the 'match 2nd harmonic to 12th fret' method, it's inaccurate and prone to error, and is actually a method only for when you don't have a tuner.

    Use a tuner to check the open note, fret 1 and every 2nd?/3rd?/4th? fret up to the highest played fret on the string (which is the highest fret for the higher strings, but E and B strings may be difficult to intonate up to the highest fret depending on their stiffness).
     
    Last edited: May 18, 2019
  15. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    This has been asked twice already...let me be the third:

    Did you set your witness points at the nut & bridge? If not familiar with the term or process, please let us know.

    Riis
     
  16. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    Apologies for missing the question, I don't know what a witness point is.
    But the bass pays fine and the intonation is good now.
     
    Last edited: May 19, 2019
    Zooberwerx likes this.
  17. Zooberwerx

    Zooberwerx Gold Supporting Member

    Dec 21, 2002
    Virginia Beach, VA
    Ding-ding-ding! This may very well explain the wonky measurements you described. Establishing witness points...which delineate the true vibrating path of any string...is essential. Here's the procedure in a nutshell:

    *Depress each string firmly on the leading (fingerboard) edge of the nut & bridge. Use your thumb and really bear down on it to create a clean break or bend. The larger gauge strings are particularly resistant.

    *Irrespective of what others have said, you can quickly check your intonation by comparing the 12th harmonic vs the 12th fretted. I'll bet $2 that your 12th fretted is now flat to some degree...advance your saddles forward until the two match. You are using a tuner, correct?

    Riis
     
    ctmullins likes this.
  18. subdude67

    subdude67

    Jan 18, 2010
    Kenya
    Thanks Riis,
    Thanks for the eplanation
    I use a tuner, correct.
    All 4 strings were actually sharp and after getting the intonation set I measured the length between the saddles and the nut and the scale length was on avarage 4mm short of a 35 ich scale and I thought that was remarkable, that's all. :)
     
  19. ixlramp

    ixlramp

    Jan 25, 2005
    UK
    How have you determined it is good? If you have only checked using the 2nd harmonic-12th fret method that can be inaccurate and is prone to error, whether you use a tuner to do that or not.

    The reason i described a more careful intonation method is due to your mysterious situation where you really need to check intonation as carefully as possible.
    Checking the open note and the octave fret isn't good enough, you need to check up to the highest played fret, and checking fret 1 is essential too, because the open note can be out of tune with fret 1.

    And yes, do set the witness points, i do this by pressing down on both sides of the nut and saddle, it's more effective.
     
  20. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    before:
    [​IMG]

    after:

    [​IMG]

    do this at nut and saddle, especially on the thicker strings, and you'll find the intonation offsets go back closer to normal.
     
    Zooberwerx likes this.

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