Modal Analysis of Solid-Body Guitars

Discussion in 'Basses [BG]' started by westland, Nov 6, 2005.

  1. westland


    Oct 8, 2004
    Hong Kong
    Modal Analysis

    I've been curious about vibrational modes of solid bass bodies, but have found most of the analysis covers Chladni patterns for acoustic instruments like the violin or acoustic guitar. Anyway, I found this site that has some nice graphics, and probably is reflective of the vibrational modes seen in electric bass (maybe reduce the frequency peaks by about 40% to reflect the larger scale of a bass).

    This suggests where you might find (and resolve) problems with dead spots, sustain, and tonal richness.

  2. Groundloop


    Jun 21, 2005
    I'll have to check all that out again in the morning after I get some coffee in me. As a theoretical study it seems very interesting, but I think most of the theory would go out the window when applied in a real world situation with the instrument held in playing position, one hand on the neck, a forearm perched on the upper bout and the back of the bass gently rocking back and forth across a convex surface. :D

    This did remind me of an article I saw years ago about an acoustic guitar builder that would put the guitar tops on a table that he could set to vibrating at various frequencies with a small electric motor. He sprinkled sand or something on the top to see the patterns that the grains would form into, and he used this as a guide to custom shape and carve each top, staying within the "it's still has to look like a guitar".

    Anyway, interesting looking stuff. I wonder how much actual research goes into solid body instrument design, instead of "They're doing this and selling a ton!"-think.
  3. westland


    Oct 8, 2004
    Hong Kong
    The sand on the top of an acoustic is a way of 'drawing' the Chladni patters. But acoustic guitars depend on the top plate for their unique sound. Electrics depent on the p'ups and the instrument itself -- maybe 60% neck, 40% rest. And true ... hand on the neck has got to change the situation ... but how? and how much?

    Anyway, I found the study fascinating.
  4. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
  5. i like the wee .gifs illustrating the torsional vibration :)
  6. BurningSkies

    BurningSkies CRAZY BALDHEAD

    Feb 20, 2005
    Seweracuse, NY
    I used that for a project I was working on...I've actually posted it here once, when debating pickups/tone/wood with another TBer. Good stuff. Glitter nodes and such.
  7. westland


    Oct 8, 2004
    Hong Kong

    You can see how important the neck is. And why the solution to dead spots is to multiply and stiffen with the likes of graphite composites (e.g., in Modulus basses)
  8. bucephylus

    bucephylus Supporting Member Commercial User

    Aug 18, 2002
    General Manager TecPadz LLC
    True, but a more subtle question is the extent to which different wood grain patterns in different necks either create a pleasing response or a "dead spot." No doubt increasing stiffness resolves the issue from a resonance standpoint. However, what is needed is a model which can sort out the sweet wood necks from the clunkers.

    Good finds. Thanks for posting.

    Another site I've been studying is not directly related, but has a lot of reference material: