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How does humidity affect string height/tension?

Discussion in 'Setup & Repair [DB]' started by Chris Fitzgerald, Mar 31, 2001.

  1. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    Played a trio gig tonight in the usual club after having also played one there last night. Last night, the weather was dry and clear, and playing the bass felt like the easiest thing in the world - action felt comfortable, the sound was strong and clear, everything was great. Tonight when I played, my bass felt like it was strung with steel bridge cables, and the sound was muddy hell....I'm wondering how much the weather could have had to do with that, and how much was just me? It has been raining all day, and I had a gig like this last year on a rainy night, and the same thing happened. So what's really going on with the bass when it gets humid? Do the strings actually get higher or lower? The strings on my bass felt like they had about twice as much tension as usual tonight. Do barometric pressure changes also affect the bass, and if so, how? Does high humidity always make the sound muddy, or is it more complicated than that?

    Any and all replies welcome.
  2. Chris, I used to have the exact same problem, before I got both a humidifier and a de-humidifier for the room I keep my DB in. The best explanation for the string height phenomena is that the wood is, after all, a porous material and when the weather is dry, it shrinks slightly, which sometimes straightens out the neck and lowers the action automatically, then when it is humid, this adds moisture to the wood, which makes it more resilient possibly causing swells in the body, and possibly causing the neck to bow slightly, thus raising the action.I have a theory on the muddy sound thing, but I want to check on it first.
    BTW in addition to the Humidifiers, a hygrometer is also a good idea, so you can measure the level of humidity in the air. I got mine for $15 at radio shack.
  3. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY

    Thanks for the info. I already keep the room I practice/store my bass in at 50% humidity year round (or attempt to with the humidifier/dehumidifier). This is a must for me because I also have a 64 year old grand piano in the same room, and when I don't do that, I have to pay a fortune in piano tunings.....what happened last night happened in the span of about 7 hours - I had a lesson from 2-3, and rather than drag my bass back into the house and then back out again for my 10:00 P.M. gig, I left it in my car (parked in a heated garage). I don't keep a hygrometer in the garage, but it never seems very humid in there unless there's a flash flood going outside.

    Anyway, last night the change seemed to take place (or at least to get much worse) during the gig. Is it possible for the changes to happen that fast? (I'm guessing that it is, since it sure felt like it...) If so, would it be stupid to try to lower the action on breaks when this happens? I always get a little queasy when doing that, since it's so hard to find that "sweet spot", and when I do, I'm hesitant to change anything. On the other hand, my fingers were killing me...
  4. Don Higdon

    Don Higdon In Memoriam

    Dec 11, 1999
    Princeton Junction, NJ
    I would rather suggest that it's the top that's moving with changes in humidity/season. Barrie Kolstein writes of having winter and summer sound posts for the same bass. The top, with it's thinness and arching, seems more vulnerable. My Mirecourt changes as much as 1/4''.
    Like reedo, I have 2 humidifiers and 1 dehumidifier for the bass room.
    I always thought one of my basses sounded better in the winter. The real reason was that it was closest to the furnace room. Then one day the top just spontaneously split from being too dry.
  5. I can't say whether that's a good thing or a bad thing, Chris, But I will say that's what I do. I have my adjusters marked so I know how far they've been adjusted, and my fingers are a lot happier. And yes, it is possible to change that fast. Here is another horror story. I was playing a recital in a small auditorium. I played the dress rehearsal, and everything was fine, so I left the bass in the hall, because I was coming back that night to play. I didn't know that they had the friggin' furnace turned up full blast, though, and when I got there that night, The fingerboard had separated from the neck! It was definitely a Bad scene, but I learned a lesson.
    BTW,I did some research on the Humidity vs. crappy sound thing, and there is an incredible amount of
    acoustic research that has been done. Some people have devoted whole theses to the subject.
    I can't possibly relate everything I found in a nutshell, but it has to do with air pressure and dampened frequency. To sum up, soggy weather=soggy sound , Dry weather= Dry, "pingy" sound, (like you didn't already know that, huh?);)
  6. Bassturbator

    Bassturbator Guest

    Jan 26, 2001
    Show-Low, AZ
    Sometimes you have to be carefull with thoes humidifiers and dehumidifiers, unless you are going to keep the bass in the room permanently. Taking the bass out of a relatively dry room out side where it is humid (or vice versa) is exposing the bass to a rapid changes of atmosphere. And rapid changes in humidity can cause serious problems like the top splitting or fingerboard separating. It is best to help the instrument acclimate to the surroundings. This can be accomplished by wrapping the bass in a material that slowly lets moister pass through it(like silk). If when you are not using it the bass is always covered with this material the atmospheric changes will happen slowly and the bass will accclimate. Then you can get rid of the humidifiers, dehumidifiers, dampits ect...
  7. Don Higdon

    Don Higdon In Memoriam

    Dec 11, 1999
    Princeton Junction, NJ
    You just don't stop, do you?
  8. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY


    Actually, at this point in my life, I find the subject fascinating - a fact that would be certain to amuse my old undergrad Acoustics professor, since I obviously wasn't very interested then...If you can post any links to some scientific sources on this phenomenon, I'd love to read them. Of course, I have noticed that soggy weather = soggy sound, but I still suspect it's more complicated than that, since (in my experience at least) it doesn't seem to always act that way every time it rains.

    When you say you "mark your adjusters", what does that mean? Just a dab of paint on the wheel to let you know how far you've changed it? And I know this has been mentioned somewhere before, but is it about a whole tone that you should detune the bass before adjusting?
  9. Jeff Bonny

    Jeff Bonny Supporting Member

    Nov 20, 2000
    Vancouver, BC
    How much are you guys paying for a humidifier/dehumidifier system. The comment about the piano caught my attention as I'm thinking of installing a small '20's Chickering grand in my living room. Seems to me the good in case cello setups are several hundred bucks? Curious as to what you're using and +/-'s.
  10. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY

    Our downstairs furnace has a built in humidifier, so that's not a problem...I keep a dehumidifier in my music room, and I think I paid something like $150-175 for it. You can get a system that attaches to a grand piano for about $300-400, but if you also store a DB in the same room, you're probably better off just dealing with the whole room at once.
  11. Jeez, I didn't think those piano sysrems were so expensive, But yeah, I got the medium size room dehumidifier for about $169(?) I don't exactly remember, but the convenient thing is, with the larger one, you don't have to empty it out every day in the summer.
    And yes, all I am talking about is marking the adjusters with a black dot, magic marker works fine for me.And a whole step to adjust is not necessary, but recommended for easier turning and less pressure.
    I'll post some acoustic sites tomorrow, I just got back from the Sat. night gig and I'm beat..zzzzzz
  12. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    Yeah, the piano systems are expensive because they're automatic. They have hygrometers built in, so that they humidify or dehumidify automatically as needed. All you have to do is fill the tank when the little red light starts flashing.

    By the way, my dehumidifier has a problem - when the weather isn't hot outside, the condensation coil freezes up, and then it doesn't work until you let it melt. Anybody else seen this happen?
  13. A dehumidifier works just like an air conditioner.
    There fore, if the ambient temperature is low enough, the condensation will freeze on the coils.

    In a previous life I was an avid woodworker. In fact I turned an avocation into a vocation and started a furniture and cabinetry business. Now you know where my handle came from. In the process I became quite familiar with the characteristics of the different varieties of wood. To this day, I still marvel at how an instrument made of differing species of wood, glued together in a way that any woodworker will tell you should not be done, and do not have a greater incidence of splitting and cracking.

    Mark Parsons
  14. Okay, you asked for 'em and here they are:

    For Basic sound characteristics this one is not bad-

    For a look at the effects of humidity on wood-

    If you're bored, and want to calculate how humidity affects sound speed-

    For all your other acoustical questions, this site has a link for it-

    It's hard, though, to get an exact answer hidden in all the scientific mumbo-jumbo. They do very well at explaining How it works but the why and
    wherefores are a bit harder to decipher.
  15. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    Thanks for the links.

    Wow, that's some pretty diverse and (in some cases) deep reading. I just skimmed three of the four...I'll probably print those this week and take a closer look. I wonder how fast these effects effects on wood can take place?

    Aside from actually adjusting the string height, has anyone found a particular kind of EQ tweaking to be beneficial in a humid environment to help cut through, or is that a hopeless battle?
  16. That is a never-ending Battle, and one I have never been completely satisfied that I have overcome. It's not just the different venues, it's also the climatic conditions of each that make it a
    constant struggle. There are times when I feel I am spitting out razor blades, the sound is so trebly standing by the amp, but then 15 feet out in front of the bandstand, it still sounds like mud.
  17. Don, I think that in fact your bass just "burst with pride" when it realised just who was playing it...



    - Wil
  18. Don Higdon

    Don Higdon In Memoriam

    Dec 11, 1999
    Princeton Junction, NJ
    ....hmmm.......waiting for the other shoe to drop.... Thanks........I keep looking over my shoulder........
  19. I am in Alaska where it does not get super humid. the winters are bone dry and the summers have some moister but not much. I was wondering if I should consider getting a different soundpost cut for the up coming weather change? what difference in humidity would require this change?
  20. Sam Dingle

    Sam Dingle Supporting Member

    Aug 16, 2011
    New Orleans
    I have a situation with my bass. I strung it up with Evah Weich strings two days ago and they sounded/felt great. Today they were fine, I left them in a cold room for an hour and when I came back the tension was crazy high and the notes sounded dead. Is this due to the cold room or are the strings breaking in?

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