Lowering action on an Acoustic Bass.

Discussion in 'Hardware, Setup & Repair [BG]' started by ADbassman, Nov 30, 2004.

  1. Now, I know how to setup an electric bass pretty good, but my acoustic bass doesn't have an adjustable bridge, and adjusting the truss rod doesn't seem to be working very well. The action on this thing is high, and I mean high. I'd like to figure out someway to lower it, any suggestions?
  2. DannyB


    Aug 17, 2004
    Although I do not play an acoustic bass, I do have an acoustic (that other thing...)

    Pretty much, your options are to file the nut, file the saddle (you can make the grooves deeper, pretty much like filing the nut, but make sure you leave enough angle to cut the note off).

    If this doesn't work to your liking, you're pretty much looking at taking the bridge off and sanding it down on the bottom (and there isn't much room to work with there).

    Other than that, you've got what you've got... So I've learned with an acoustic "that thing"
  3. bluemonk


    Dec 17, 2002
    What about if the bridge has a piezo pup under it? does that make sanding from the bottom impossible?
  4. It is an acoustic electric, but I'm not sure about the position of the pickup in it, maybe I can shove a mirrior up in there and have a look see.
  5. DannyB


    Aug 17, 2004
    I was assuming acoustic... acoustic electric might not be possible to sand the bridge if there is a piezo in bridge like bluemonk said... Take a look and figure out where and how it's all rigged up and use your imagination
  6. I assume you are talking about an acoustic bass guitar(?)
    When I had mine,and I needed to lower the action,I just loosened the strings,and turned the saddle around 180degrees...it worked very well,but maybe it was because of the wear on the saddle...but it may also work for you...
  7. My Carvin AC40 has an accoustic type bridge. Although, I like the action very much, I'd say the way to lower it would be to take the bridge saddle out and sand the bottom of it. You won't have much to work with and if your action is way too high, then the problem is not the bridge anyway, it would be the neck angle.

    For best results, take it to a luthier and have it checked out.
    Lownote38 likes this.
  8. mikezimmerman

    mikezimmerman Supporting Member

    Apr 29, 2001
    Omaha, Nebraska
    Pretty much what everybody else said--the bridge saddle is normally removable, and the way to lower the action is to file the saddle from the bottom to make it shorter. If you decide to do it yourself, be sure you keep the bottom flat--it has to press down evenly on the pickup underneath (if there is one), and if it doesn't the string-to-string balance will be uneven when amplified.

    However, one thing I've found is that for purely acoustic volume, a higher action is better--it drives the top with more force, and allows you to play harder without buzzing the strings. The luthier who built my ABG actually supplied me with 3 saddles of different heights, and after trying them all I've kept the bass set up with the highest one.

  9. Well, after a couple of days (yes, days) of adjusting the truss rod, it seems to have gotten to a decent level, feels a lot better and plays a lot fast now. I don't think I'll be sanding the bridge soon, but thank y'all for the suggestions.

  10. Glad to hear that everything as an acceptable level. I will agree with mikezimmerman in that an accoustic should have a slightly higher action than an electric (same is also true for guitars). It has to do with getting the instrument to "talk".

    I am not surprised that the truss rod adjustment took a couple of days to sort out. It often takes time for everything to settle out.

    Have fun.
  11. fvincent


    Sep 10, 2012
    It is a slow process. Tune to pitch. put a quarter between the string and the fret at the 12th fret. The string should just touch the quarter. If its to high, looseb the strings and sand the bottom of the bone saddle with 60 grit a little at a time. Put it back in and repeat. Sand until the string just touches the quarter. Done!
  12. mech

    mech Supporting Member

    Jun 20, 2008
    Meridian, MS, USA
    If the bass has a piezo element under the bridge saddle do not try to sand the bottom of the saddle. It must be as flat as possible to have even pressure on the piezo element and hand sanding will not leave it flat. Uneven pressure can cause the piezo element to break or have unequal output string to string. I've made a good deal of $$$$ fixing acoustic instruments with the action lowered by that method. The most reliable method to my knowledge is to slot the top of the saddle one string at a time with the other strings tuned to pitch to keep pressure on the piezo and the saddle from rocking in it's slot which can stress the piezo. If working with a compensated saddle, keep the witness points of the strings in mind when finishing the slots.

    Some instruments have shims under the piezo element/saddle that can be removed to lower the action. Doing this can mean removing the saddle/piezo several time to get things right. I prefer to disturb the system as little as possible and slot the top of the saddle. YMMV.

    It is a slow process. When you get to the point where you think you can take one or three more passes with the file to get it perfect...STOP.

    Good illustration of a compensated saddle with witness points highlighted from the interwebs.
  13. Pilgrim

    Pilgrim Supporting Member

    Buy a couple of matching saddle blanks from Stew-Mac. Remove the original bridge saddle and use it as a template for a replacement. Cut the replacement much shorter than the original - DO NOT alter the original. Save it untouched, so you have a path back to stock if you screw up the replacement.

    Insert the newly shaped saddle and play with it for fit.

    I agree that care must be taken when sanding the bottom of your NEW saddle (don't mess with the old one), but here's one way to do it right:

    When sanding the saddle down to height, glue sandpaper on a piece of marble or plate glass; sit a 2x4 on the flat surface and slide the saddle up and down along the 2x4 using it to keep the saddle at 90 degrees to the sandpaper. This makes it easy to shorter the saddle and keep a 90-degree, absolutely flat bottom edge.
    Last edited: Apr 4, 2015
    JonathanAlvarez likes this.
  14. JonathanAlvarez


    Aug 31, 2016
    I did as you said and it works like a charm. Way easier to play now.
    Thanks for the idea.