Tuning instability : possible structure problem?

Discussion in 'Setup & Repair [DB]' started by luisraulmunoz, May 14, 2019.

  1. Hello I have experienced tuning instability with my bass particularly when changing places (my house vs symphony Hall etc.)

    Part of this is of course difference in humidity and temperature from air conditioning in the symphony Hall vs my house. Now my bass is about 90 years old so that might be a factor, it would take about 1 hr adjustment period when going to the hall.
    Then even after that I would have to re adjust tuning during rehearsal.

    So my question is what are the main factors at play.
    My tuning gears sre crappy, not smooth and we're poorly installed.
    But also a luthier once did some work on the nevk and might have thinned it out too much do I don't know if this might be at the root of the long periods required when changing venues for tuning to stabilize.

    I include photos of the nevk for reference; does it look too thin proportionally? I would love to hear opinions. Because if that's the case I need to get a new neck...

    Attached Files:

  2. A bass of that age should be relatively stable, so the wood probably isn’t moving as much as a newer bass might tend to.

    The neck thickness and set look reasonable.

    I assume the strings are steel.

    If most of your tuning is in an upward direction and not equivalent across the strings, I’d look at the machines.
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  3. Steven Ayres

    Steven Ayres Supporting Member

    Mar 11, 2007
    Northern Arizona
    This alone is enough to cause the sort of change you describe, particularly the humidity (noting that you're in Puerto Rico). Is this a problem you weren't having under the same conditions up to some point in the recent past?

    Regardless of the cause, this cycling probably isn't good for your instrument, it's hard on joints and soundpost. If you can't keep it climate-controlled at home, you might look into the possibility of keeping it at the hall between performances.
    luisraulmunoz and Tom Lane like this.
  4. Ok thanks. I just assumed an older bass would be more susceptible to the humidity/temperature change.

    The strings are steel. The machines are very irregular and I always feel not properly installed (they came with the bass) I believe a period of adjustment is to be expected because the air is colder and a bit less humid (not very dry) in the hall.
    The problem is that even after a while I need to keep on tuning the instrument. And sometimes tuning one string will make the other change a bit as well. So after your comment I'm thinking the (relative) chaos might be due more to the tuning gears working against each other.

    But still even in my house the instrument will go up (and the bridge will raise to some degree) when for example it rains heavily. Puerto Rico h(tropical) humidity is more extreme than I experienced in the States (Indiana) or in Europe (Geneva Switzerland).

    Whenever I would bring this or any other bass back home the instrument would change and the bridge would go so much higher the first day back.

    Still the instability the past weeks has become worse so if you don't see a problem with the neck thickness I have to think it's mostly the gears. Not sure what other factors would contribute.
  5. The thing is I had not been using this bass at the symphony Hall for quite a while. I'd just keep it at home. It's normal for some change to happen since my home does not have central air conditioning, what worries me is that even after that adjustment period the tuning kept on being somewhat unstable. Had to keep adjusting one string and then another etc. Must be when I tighten one string another loosens or something so must be gears are unstable.
  6. unbrokenchain

    unbrokenchain Supporting Member

    Jun 8, 2011
    Black Mountain, NC
    What is your tailgut material? I've had minor relative tuning issues with the nylon cord type, not so much with steel cable. The neck doesn't look bowed in the photos, has the scoop in the fingerboard increased at all (strings higher off the board near the heel but closer to the board in thumb position)? Also wondering if the instrument doesn't need a longer soundpost for its more humid environment, not sure if too short a post could cause this issue though.

    Nice bass btw!
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  7. wathaet


    May 27, 2007
    This sounds normal to me. Many halls are cold when you tune and get warm when the lights are on and the whole orchestra is there causing strings to go flat. Always tune with warm strings.
    This issue is even worse in concerts at some halls. A drier hall will do the same.
    How much varies from string to string, but synthetic strings like Evah are almost immune as they don’t expand with heat and their elasticity makes them react less to top movement.
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  8. If the neck was unstable in a way that affected the tuning, you should be feeling a clear difference in action/string height also.
    Last edited: May 15, 2019
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  9. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    Are you always re-tuning tuning up, or in both directions? If the former, the tailgut could be the culprit. Also, show us a photo of the pegs. I presume you know how to install strings, but we might as well rule that out first.
    luisraulmunoz likes this.
  10. wathaet


    May 27, 2007
    It would be useful to know if it sinks a few HZ which is normal or noticably more which is not normal.
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  11. bengreen


    Jan 26, 2016
    San Diego
    May have no link to yours, but had a similar problem once. Took bass to Lisa Gass and she found lower half of fingerboard had come unglued from the neck. I couldn't see it or feel it until she pried them apart to show me.. Reglued lower half and problem went away. Strength of neck relies on "plywood" the two pieces form when glued together.

    Most of what you describe seems normal behavior...tightening the low strings pulling the high strings flat, all flattening during initial play/warm-up, pitch change with location change...except on my basses all more or less stabilize after about 10 to 20 min max. An hour seems long.
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  12. wathaet


    May 27, 2007
    With say 20% lower humidity I can have pitch drop for four hours easy.
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  13. Steve Swan

    Steve Swan

    Oct 12, 2004
    Burlingame, California
    Retailer: Shen, Sun, older European
    At first glance, it does look like the maple in the neck has been thinned some. The fingerboard is the backbone of the neck and looks healthy enough in thickness. Do you have some measured thicknesses to offer us ?
    luisraulmunoz likes this.
  14. Thanks, the tailgut is synthetic rope but not nylon, can't remember where I bought it exactly...but its been there for several years. Hadn't thought about the soundpost it's probably on the short side as I don't like them too tight. That might be an important factor. Would you say a shorter soundpost could cause more sensitivity to temperature/humidity?
  15. True, in my experience it's normal to a point, it's just been more problematic than I can remember it being before.
  16. unbrokenchain

    unbrokenchain Supporting Member

    Jun 8, 2011
    Black Mountain, NC
    My (limited) understanding is that the whole instrument swells with humidity, which slightly increases the distance between top and back plates. If the post was cut in a much different environment, there might be more top movement in the humid environment than ideal. Again I'm absolutely not a luthier but it's one hypothesis.

    Might also check the fingerboard glue joint as Ben Green suggested, and you'd probably be having other big issues if the bass bar was loose, but might as well look in there with a flashlight and mirror and rule it out?
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  17. Eric Hochberg

    Eric Hochberg Supporting Member

    Jul 7, 2004
    I'd get braided steel to replace the rope, which could be losing strength and stretching after years. If that doesn't help, then maybe time for new tuners if the rest of the possibilities are ruled out.
  18. robobass


    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    +1. I Had a fancy and expensive rope tailgut installed once. Everything was fine for like a month, but then the bass started losing pitch every day. I couldn't figure out why until the day it broke.
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  19. rknea


    Jan 16, 2007
    Queretaro, Mexico
    I have this issue on my '39 Kay as well...even just keeping it in my house. Always having to tune it up. I took it out to a gig last week and tuned it twice when we got there and again between the 2 sets we did.
    luisraulmunoz likes this.
  20. Tailgut is a cheap experiment. If you’re handy you can replace it with a braided steel cable and a hammer-close fastener for under $3 at a big-box home improvement store.

    I briefly tried a synthetic tailgut. Cute concept, but in practice it stretched excessively and sounded dull compared to steel cable.