Results 1 to 11 of 11

Thread: Intonation Mystery

  1. #1

    Question Intonation Mystery

    Hello all - Im in a bit of a pickle. Background: i know my way around working on instruments, novicely. On my Eastman mandolin - tune to pitch, check harmonic nd 12th fret...they are the same, so that tells me the bridge is proper in place. BUT when I fret, for example, 5th or 7th fret (bot exclusively) they go sharp? Is this a fret problem? Or is the neck bowed r something? Thanks in advance.
    Last edited by EddieFrank; Nov-23-2021 at 2:11pm.

  2. #2
    Registered User sunburst's Avatar
    Join Date
    Nov 2003
    Location
    Kentucky
    Posts
    15,182

    Default Re: Intonation Mystery

    Only 5 and 7 are sharp? If it is two frets only, and all strings are sharp at those frets, that is inaccurate frets. If other frets are also sharp, it could be the string nut; either string notches too high or inaccurate placement. If only some strings are sharp it could be the strings or the string set.
    BTW, it is impossible to get all strings of a set in perfect tune at all frets (the closest I've ever accomplished was +/- 3 cents everywhere, and at that point improving one string/fret was going to make it worse at another fret.

    Going through a step by step set up should minimize intonation issues.
    1. check neck relief
    2. check frets, If they are not properly level they must be attended to before a set up can be accomplished.
    3. adjust string height at the nut if needed
    4. adjust action height at the bridge
    5. re-check neck relief under string tension and adjust as needed

    If the frets are in good shape and properly leveled, if the neck is properly straight (a tiny bit of relief is usually good), if the nut slots are correctly cut for string height, if the action is reasonable, and if the strings are relatively new and in good condition, we've eliminated all of those things as the cause, so any intonation problems are the result of some inaccuracy somewhere.

  3. The Following 2 Users Say Thank You to sunburst For This Useful Post:


  4. #3

    Default Re: Intonation Mystery

    Hey thanks for reply - No, it's not only 5& 7, I just used that for example. I will edit the post. Thanks for the tips.

  5. #4

    Default Re: Intonation Mystery

    I can say its probably not the strings themselves, as it is an ongoing thing I've been trying to figure, at least 3 sets worth( meaning probably 4 months)

  6. #5
    Registered User sunburst's Avatar
    Join Date
    Nov 2003
    Location
    Kentucky
    Posts
    15,182

    Default Re: Intonation Mystery

    If it's other frets also, I'd check the string height at the nut first.

  7. The Following 2 Users Say Thank You to sunburst For This Useful Post:


  8. #6
    Registered User Mike Conner's Avatar
    Join Date
    Mar 2011
    Location
    Murphy NC
    Posts
    235

    Default Re: Intonation Mystery

    If I understand your description correctly, the 12th fret harmonic and the 12th fret fretted pitch are a good match. Most mandolin bridges have a staggered compensation for the individual string pairs - the A strings saddle point is typically moved back towards the tailpiece. Sometimes, and I have seen this several times on imported guitars, the intonation can improve for frets 3 through 7 by moving the nut slightly towards the first fret, leaving all the other fret positions per the standard calculated distance from the first fret.

    On my guitar and GOM builds I incorporate this compensation in my fret position calculations and cut the slots accordingly. The compensation I use is 0.013" less from the nut to the first fret. When refretting guitars a new nut is usually needed also, and I have a razor saw with a 0.013" kerf blade, so it is easy to saw between the nut and end of the fretboard, file everything clean and smooth, and glue the new nut in the modified position.

    Follow Sunburst's guidance first, and if everything else seems correct, perhaps consider whether moving the nut slightly closer to the first fret could help.

    Before reworking the nut position, I would move the bridge slightly towards the tailpiece, letting the 12 fretted pitch be slightly flat, and see if this moves your other fretted pitches in the right direction. Easy test to perform before starting any surgery ;-)

    If you are anywhere near Murphy NC I would be happy to help...

  9. #7

    Default Re: Intonation Mystery

    Hey thanks for the info - I had thought about trying to position the bridge so that 12th fret is a hair flat - I nearly never play those notes.
    Oddly - Im in Asheville! I love the Murphy area.

  10. #8
    Registered User sunburst's Avatar
    Join Date
    Nov 2003
    Location
    Kentucky
    Posts
    15,182

    Default Re: Intonation Mystery

    Quote Originally Posted by EddieFrank View Post
    ...I had thought about trying to position the bridge so that 12th fret is a hair flat - I nearly never play those notes...
    Many people don't play those notes regularly, and I have suggested to them to place the bridge for better intonation on the frets where they do play regularly.

    BTW, I shorten the distance from the nut to the 1st fret on new builds but only occasionally do that to a completed instrument. If the nut slots are cut correctly (so that the string height is the same as the fret height or perhaps a couple of thousandths higher) the first 3 frets are usually no more than 3 or 4 cents sharp, and most people can live with that just fine. The effect on intonation of shortening the fingerboard is pretty much the same as lowering nut slots that are too high.

  11. The Following 2 Users Say Thank You to sunburst For This Useful Post:


  12. #9
    Registered User Mike Conner's Avatar
    Join Date
    Mar 2011
    Location
    Murphy NC
    Posts
    235

    Default Re: Intonation Mystery

    Quote Originally Posted by EddieFrank View Post
    Hey thanks for the info - I had thought about trying to position the bridge so that 12th fret is a hair flat - I nearly never play those notes.
    Oddly - Im in Asheville! I love the Murphy area.
    If in the end you are not satisfied with your results, or if you happen to plan to be in the Murphy area, message me and I'll try to help.

  13. #10
    Dave Sheets
    Join Date
    Feb 2015
    Location
    Buffalo NY Area
    Posts
    421

    Default Re: Intonation Mystery

    Strings too high off the fingerboard at the nut cause this effect, as mentioned earlier. That might not be your problem, but I've seen it on many, many instruments.

    Good luck with it, if it's the problem at the nut, it's an easy fix.

    Happy Thanksgiving!
    -Dave
    Flatiron A
    Way too many other instruments

  14. The following members say thank you to Dave Sheets for this post:


  15. #11
    Registered User briankwood's Avatar
    Join Date
    Feb 2010
    Location
    Northern California
    Posts
    17

    Default Re: Intonation Mystery

    I've found that shortening the distance from the nut to first fret a few thousandths helps this problem. It can be done by cutting the fingerboard. Try experimenting by sliding an E string under the strings against the existing nut. That will shorten the distance to the first fret by half the diameter of the string and give you an idea if that's enough or too much compensation.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •