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Why Not More Contact Points on Bridge Question

Discussion in 'Setup & Repair [DB]' started by Bin Son of Bin, Mar 27, 2013.


  1. Ok, this is a question regarding the bridge and the physics of it I suppose. I am not a Luthier so I am surmising a few things here and please correct me if I'm wrong.

    As I understand it, the string vibrates and the vibration travels down the wood of the bridge to, in part, impart the sound into the body of the bass.

    This transfer of energy is made by the two contact feet of the bridge, one foot neart the sound post and the other over/near the bass bar which transfers more of that bass side energy along the body.

    Now, my question is this: Why have spaces between the feet? Would not having a bridge that has full contact with the body provide more of the energy along more of the surface of the body?

    So imagine the gap of the bridge between the feet gone and instead it's solid wood. I'm sure there's a reason why the bridge is the shape it is but I was just wondering about this idea.

    Or......

    What if you had 2 or 3 or 5 bridges, the extras not so much there to take the brunt of that presure from the strings but to transfer more energy or different frequencies or some such...

    ps: I'm tired and at work and have been at work for 11 hours. Please be kind.

    Jason
     
  2. RSBBass

    RSBBass

    Jun 11, 2011
    NYC
    I think that if you had a solid base you might dampen as much as you added if not more. I have seen three footed mandolin bridges but not on bass or other "violin family" instruments.
     
  3. Well, your argument would be perfect, but adding more wood dampens vibrations. Plus more contact points would do the same.
     
  4. Hi Jason.

    Interesting questions.
    The "solid" wooden bridge and a three and IIRC 4 point aluminium spiderlike bridges have been either experimented or even sold as replacements.

    For more than 3 point contact to the top though, the ancient carpenters saying that: "a 3 leg stool never rocks" holds more than true.
    More than 3 legs won't work well since additional feet will always transfer less than the three in full contact.

    The thing with an arch-top bridge isn't as much as to transfer the vibration, but to transfer it in a controllable and predictable fashion. The bridge also shouldn't restrict the top from vibrating, and while a one legged bridge would be ideal for that, it's obviously not that practical approach ;).

    AFAIK there's been X-braced experimental "DB"s, but the results were not as good as predicted. Partly that can be because we are tuned to how certain things in music sounds, the first sine-wave synths for example were totally ignored in piano playing circles because of the non-musical, sterile tone.

    The DB and DB construction we have at the moment has only evolved for a few hundred years at this point though, so there may well be further evolution just around the corner ;).

    Regards
    Sam
     
  5. dbassnut

    dbassnut

    Apr 1, 2008
    Malaysia
    I think one of the reasons is also that even though you're transferring energy from the strings through the bridge to the top of the bass, the bass feet are also dampening the vibrations on the bass plate. Is this correct?
     
  6. robobass

    robobass

    Aug 1, 2005
    Cologne, Germany
    Private Inventor - Bass Capos
    I remember a bridge which was conventional except that it had no heart and a ribbon pickup ran across the entire width where the heart would normally be. I saw a few of these in NY in the early '90s but never tried one. Intuitively it seemed like a bad idea. It might be psychological, but anything that restricts normal vibration - wing pickups or the clamps on a BP-1 - makes the bridge feel "dead" to me. It may not actually affect the sound so much, but the effect on bowing response alone (and I also sense it when plucking) makes me avoid tampering with the normal vibrating parameters. The conventional design has evolved over centuries, after all, and if it weren't the best it probably would not have become so universal.
     
  7. Heifetzbass

    Heifetzbass Commercial User

    Feb 6, 2004
    Upstate, SC
    Owner, Gencarelli Bass Works and Fine String Instruments, LLC.
    Well, if one driver sounds good on a speaker cone- won't six drivers sound better?:p

    The bass bridge is centered on the "drive" area of the top and the engine of the bass is the bass bar while the soundpost is the coupler that helps the top and back "wave" in phase. There is much research by George Stoppani to explain these ideas more. More bridge feet would put the top out of phase and you would lose energy rather than gain it. If the bass bar is tuned properly, the soundpost is well fit, and the bridge fit positively with the proper mass/weight you will have a very efficient engine.

    However, by all means experiment! Just be careful not to damage the top!

    Best,
    Brian
     

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