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Isolating body vibrations from the pickup: A Physics Question?

Discussion in 'Pickups & Electronics [BG]' started by stubbsonic, Apr 8, 2009.


  1. stubbsonic

    stubbsonic

    Apr 3, 2009
    Is there any reason why I shouldn't fasten the pickup to the body of the bass with screws? I was just thinking there might be some tiny amount of vibrations from the body of the bass that might somehow conduct (mechanically) into the pickup-- affecting the relative position of the vibrating string and the pickup.

    I'm not talking about microphonics (like from an unpotted pickup). I just mean that the pickup is not entirely stationary while it's reading the string. And is the tiny movement of the pickup substantial enough to affect tone (especially of the body's vibration has a weird phase-relationship with the string)?
     
  2. 4StringTheorist

    4StringTheorist Supporting Member

    I'll chime in and say that yes, there is an effect in theory due to the issues that you note (The pickup will have an altered motion relative to the string, which is what the pickup reads via Lenz's Law)

    However, I'd bet a shiny new quarter that any differences are inaudible in a double-blind test.

    However: I know from reading a recent Guitar World that Eddie Van Halen swears by direct bolting the pickups, and that his preferred method of checking out the tone of one of his EVH Wolfgang prototype guitars was to play one note and let it sustain into feedback.

    I can imagine (though have no data to support) that the pickup mounting will make a difference in a feedback situation... especially with those itty bitty little strings that guitars have.

    Take care!
     
  3. stubbsonic

    stubbsonic

    Apr 3, 2009
    Yea, the alternative is to try to find some material to put the the pickup cavity or some way of screwing into something that would isolate vibrations. Seems like a big pain the the a.

    I could also picture cutting a big hole all the way through the body under the strings-- cutting a piece of compressed fiberglass to fit in that opening-- mounting the pickups in that-- where's my jig saw?

    Thanks.
     
  4. Hoover

    Hoover Banned

    Nov 2, 2007
    New York City
    You mean like the springs, foam, or double-stick tape that folks have been using for decades?
     
  5. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Seems like someone is addressing a problem that doesn't really exist.
     
  6. HogieWan

    HogieWan

    Feb 4, 2008
    Lafayette, LA
    yes, there will be a relative difference, but the strings swing a LOT more than the body/pickup, so the effect is minimal
     
  7. stubbsonic

    stubbsonic

    Apr 3, 2009
    People do use springs, foam, etc. But ultimately, it's the screws into the body that are the conductors of vibration into the pickup. It's all theoretical, and miniscule as others have noted. I was just curious if this was something anyone had done any comparisons with. Don't worry, I'm not serious about hacking up my bass-- at least not for this.
     
  8. I've done it. Got tired of collapsing foam etc. and made wood shims to hold the pups at the correct height, with the screws fully tightened. No difference in sound. It was kind of a pain to do, wouldn't bother doing it again. Now I use short lengths of model airplane fuel tubing on the screws, to act as springs. Works great.
     
  9. stubbsonic

    stubbsonic

    Apr 3, 2009
    I'm installing some new pickups and will probably be fussing with the height for a little while, so I think for now it will be springs or foam. I'm not sure which gives the most useful range of "squish," probably springs, though I think the foam might be easier.
     
  10. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    I wouldn't worry about the pickup's feeble vibrations sucking any tone away.

    I routinely test pickups by attaching them in the most precarious manner. Besides pickup up handling noise, I've never noticed any detrimental effects tone wise.

    I think as long as the pickup is not wobbly, you have nothing to worry about. I've also screwed pickups right to the body with no sponge, just a wooded shim, and they didn't sound any different.

    Also if the pickup is vibrating along with the body, that could be part of the tone of the bass. But pickups mostly sense the up and down movement of the strings, and I doubt they are moving up and down opposite the string's motion. They might be jiggling microscopically, but as I said I wouldn't worry about it.
     
  11. stubbsonic

    stubbsonic

    Apr 3, 2009
    Cool. Thanks, everybody. I'm new on this forum and am really enjoying reading stuff here.
     
  12. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    eddie van halen's solution was for guitars at insanely high distortion and volume, where the whole pickup would just start vibrating by itself and produce a low/mid howling through the amps. bolting the pickup rigidly to the wood stopped it's "microphonic" resonance. i don't think even entwistle had that problem with bass pickups.
     
  13. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Put that in context. Many guitar pickups mount on springs to the pickguard. Whole different thing than screws going into body wood with some ultradense compressed foam or rubber compound against their back, as is found in a majority of basses.
     
  14. SGD Lutherie

    SGD Lutherie Banned Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    +1. The standard humbucking mounting scheme is archaic and wasn't even good 50 years ago! The pickups often wobble and can't be adjusted to match the string angle.
     
  15. mongo2

    mongo2

    Feb 17, 2008
    Da Shaw
    Where the strings intersect the pickups mag field the field is a contiguous region not discrete areas on most bass pickups (check it with EMG magnetic viewing film against the bottom of the strings to be sure). So any movement in of the pickup caused by vibrations in the body won't be relevant. Even if the field is discrete areas such as on a Fender SCPB style pickup the area is still large enough for it not to be an issue.

    A different but related issue: With an SCPB pickup and it's narrow polepieces the string excursion is more of an issue and is what I believe to be responsible for that pickup's compressed tone usually heard when the strings are not aligned properly over the poles. I solve that with a notch in the saddles or using a pickup with wider poles such as a SD Quarter Pounder.
     
  16. Pickups can be "free floating", not touching anything but foam or padding. They can be "semi floating", with foam on the bottom, held down by screws, or they could be "solid mount". I'm sure there is a sound/tone difference, but I doubt that we could hear it.
     

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