Intonation help

Discussion in 'Hardware, Setup & Repair [BG]' started by DonChalfy, Mar 11, 2002.

  1. DonChalfy


    Mar 6, 2002
    Sarasota, FL
    I just put a new set of Tomastik Jazz Flats (6 string) on my Ken Smith bass. This is completely different from the MTD medium gauge I've been using. The problem is primarily with the "B" string. If I intonate it properly--matching pitch with the open string and octave at the 12th fret, the notes from the 1st thru 8 or 9th fret are noticably flat. If I bring adjust so that the pitch is in tune on the lower notes, the notes from the 12-24th frets are really sharp. The other strings don't seem to be a problem (so far) that way. Please let me know any helpful remedies. Not to sound like an idiot, but if I need to ad some relief (bow) to the neck and the front of the bass is facing me, which direction should I turn the truss rod (left or right)?
  2. Hi, Don -

    B strings are a bit tougher to intonate. If you have access to a tuner it makes it a lot easier - but I think the reason is that since a B string vibrates at 31Hz it's pretty hard for a tuner to track. Even if your intonation was a couple of cents off that's still < a 1Hz error - pretty tough on a tuner or a practiced ear.

    I have a Korg DTR-1 - a pretty high-speed tuner and still have problems getting it to track a B string consistently. I do have a suggestion, though - it seems to be a little easier for me and might be worth a try. Someone on another forum taught me this trick (thanks, Jazz Ad).

    Try tuning the B at the 12th fret and comparing the 12th fret harmonic to it. That way you can let the harmonic ring (and watch the tuner) while you adjust the saddle. I've been able to get B string intonation closer this way than any other way - maybe it'll work for you. Here's how you do it -

    With a tuner, tune the B string at the 12th fret. Once that's in tune, check the 12th fret harmonic against it. If the harmonic is sharp, lengthen the string (move the saddle away from the neck). If it's flat, shorten the string. I only adjust the saddle about half a turn at a time because changing string length will pull the string out of tune - so adjust the bridge saddle, retune the B at the 12th fret and repeat as necessary. You'll get it.

    Smiths are set up pretty well from the factory most of the time - maybe it'd be a good idea to measure relief and see if it needs to be adjusted. Although I've never used TI flats I understand string tension is pretty low - maybe raising bridge saddles or adjusting playing technique is a better solution than adjusting neck relief.

    That said, if you need to adjust the neck, loosening the trussrod adds relief - tightening it makes the neck straighter. If you face the adjustment nut you turn it counterclockwise to add relief. IMO it's not a good idea to adjust more than 1/4 turn without letting the bass sit overnight - wood doesn't change shape easily or quickly :)

    Good luck!

  3. thumb rules :

    1) T-rod : If the neck is too much bent, turn the thrussrod clockwise ( tighten ). if it is too strait, turn it counterclockwise ( loosen ).
    Turn the 'rod 1/4th ( 90 degrees ) at a time MAX.
    Tune up and leave the bass alone for a while ( hour or so ), and then re-check.

    2) intonation : tune your string, and strike it @ 12th fret. if it is above, tighten the intonation screw ( sadle -> back ), if it is below.. loosen the screw ( sadle -> front ). tune up and try again. and the same goes here : 1/4th turn at a time.

    about the B-string... is your action high ? high strings are harder to intone than strings low to the fretboard. refer to Pythagoras for it..
  4. jamminji


    Mar 22, 2002
    And I have the same question. Lots of great info given here, thanks, but your question still needs an answer. I have seen this also. You can get the bass in tune at the nut and at the 12 fret, but the 5th-7th frets etc are still outa tune... I have no idea how to adjust this but would love to find out!!! any help here guys?

  5. okay ya'll you action must be very low to get the b string right. i finally got it after about a month of tweaking my bass... its in the process of just sitting whilst the truss rod gets all nice and cozy..

    it takes a long time to get the B right. just keep tryin combos of action height and intonation...
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