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Soundpost for hybrid- Spruce or hardwood?

Discussion in 'Luthier's Corner [DB]' started by etorgerson, Jul 10, 2018.

  1. I have a Christopher DB302 that I am trying to optimize. After reading Traeger, I’m wondering whether a hardwood or better spruce soundpost would improve the instrument- he posits that hardwood matches the plywood’s impedance and better transers the vibrations.. I just found a setter that does not use a point, so can even try carbon fiber. (I have ww tools and know how to use them - just not as a paid professional.) I plan on trying several next week, but always value your experiences.
    1. Has anyone experimented with hybrids?
    2. With plywood, what soundpost materials have worked for you?
    3, It still has the factory Christopher SPst, any thoughts on the quality?
    4. Anyone played with carbon? Braided or composite? Tubular or solid? What do you do about fitting the ends if using tubular?
    Max George likes this.
  2. Max George

    Max George

    Dec 27, 2015
    Looking forward to hearing the answers on this
  3. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    You obviously need a hybrid soundpost. Broomstick tipped with finest winter harvested Carpathian spruce should be a good choice :)
    carl h., james condino and etorgerson like this.
  4. Greg Clinkingbeard

    Greg Clinkingbeard

    Apr 4, 2005
    Kansas City area
    KC Strings
    I have used maple on plywood basses and the results have been good, although it’s nothing I feel strongly about. Although Traeger’s methods have merit, I find some disagreement.
    I tend to favor a sound post of the largest diameter which will fit through the hole. The ends are slightly rounded with the edges more so.
    After using a 7/8” maple dowel in my Kay, I settled on a piece of old fir from a paint roller stick.
    The most important factor is position and fit.
    etorgerson likes this.
  5. turf3


    Sep 26, 2011
    I've read a bit of Traeger's stuff and what made a lot of sense to me in his discussions of soundposts was the idea of minimizing (within reason) the contact patch at the ends of the post, to permit easier very slight sideways displacements of the front and back plates with respect to each other. The whole discussion about the different materials seemed a bit more of a reach to me, as wood is pretty darn stiff in compression along the grain and I would question whether there's really that much difference among the kinds of materials one might use there (I mean, yeah, balsa vs. ironwood is one thing, but maple vs. spruce is probably a lot less.

    However!!!! Take all I've written above with a block of salt, because I have never even set a soundpost, never mind experimenting with different ones. I'm just commenting from a basic perspective on the properties of materials.
  6. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    none of that makes any sense to me, as i visualize the soundpost as the one point of no vibration, with everything radiating from that nodal point. a pickup exactly at the soundpost position picks up very little sound. move it a few cm away and the change is significant. move it to the E foot of the bridge and the amplitude increases usefully.

    i don’t believe the soundpost transmits vibrations to the back.

    the position of the nodal point and particularly in relation to the bridge is critical in shaping how the top vibrates.
    Heifetzbass, etorgerson and s0707 like this.
  7. Steve Swan

    Steve Swan

    Oct 12, 2004
    Burlingame, California
    Retailer: Shen, Sun, older European
    Sliding around the small diameter contact point of a Traeger-ized soundpost against a spruce top will leave little compression slug trails on that spruce surface. Modifying the inside of the mating surface of the inside of the top by moving the soundpost against it this way will make future fitting against this now irregular surface impossible without fitting a new soundpost patch. How does this bizarre process of using a bullet-nosed soundpost actually "improve" the sound and function of a spruce top bass?
  8. Steve, I had asked that in a previous post where I mentioned that the back plate has this huge transverse ‘furring strip’ type brace that the soundpost sits on. Using a mirror, I saw a thin patch on the top where the soundpost sits. It seems like a bit of bulletproofing that would probably minimize the effects of anything I do, sort of like putting a booklet between a wall and your ear thinking that you’ll still hear the next room just as well. but you won’t get cooties.
  9. The top patch is indeed a structural reinforcement.

    Putting a center brace in a roundback bass is a Chinese thing, mostly. It seems to increase projection, in part by making the back stiffer. This makes me wonder how much energy travels through the post to the back. Very early Kays also had the brace.
    etorgerson likes this.
  10. Greg Clinkingbeard

    Greg Clinkingbeard

    Apr 4, 2005
    Kansas City area
    KC Strings
    I have occasionally domed (for lack of a better word) the ends of a soundpost for the reasons turf3 mentioned. The center of the ends never more than maybe .1mm higher than the edges. We’re talking just enough to see light when holding a straightedge on it. Generally, I leave them flat.

    No, I don’t think the post transmits much sound to the back, it’s a pivot point for the top. It’s position in relationship to the bassbar and treble side foot affect the tone more than what it’s made of. Tinker away if you have the time and energy. IMO, you might squeeze another 5% out of particular bass, but a bass is generally as good as it is when set up well, using conventional methods.
    etorgerson likes this.
  11. 5%+5%+...= better than it was.
  12. LouisF

    LouisF Supporting Member

    Apr 21, 2003
    Los Angeles, CA
  13. Thanks, I was trying to figure out options for capping the ends of a cf tube. I’m considering a composite plug in order to let the tube transmit without the extra boundaries that the Gemini brass and the really expensive adjustable design have.
  14. turf3


    Sep 26, 2011
    How about a three piece sound post, the "post" part with rounded spherical ends, each end capped off with a foot which has a spherical socket and the other side flat? This way it allows side to side movement of the front and back with respect to each other, but at the same time you can scoot it around to position it without tearing up the inside surfaces. Furthermore, it wouldn't be necessary to bevel the ends as has to be done with a standard one, to accommodate the fact that the two inside plate surfaces aren't parallel to each other.

    Has anyone tried something like this and reported the results?
  15. I saw an add for a REALLY expensive carbon soundpost that was adjustable and seemed to have ends like you describe.
  16. s0707


    Jun 17, 2015
  17. turf3


    Sep 26, 2011
    I was really just thinking of three pieces of wood to make up a sound post assembly with pivoting ends. Any competent luthier would be able to make something like this. The details of installing it might be a little hairy.
  18. powerbass

    powerbass Supporting Member

    Nov 2, 2006
    western MA
    I made a carbon fiber soundest w/wood ends as you describe for my hybrid Thompson RM200. Frankly it was an interesting project that didn't do much in the end.

    Attached Files:

    robobass likes this.
  19. Ortsom2

    Ortsom2 Banned

    Mar 17, 2018
    Sorry, no advice on what to use, other than that spruce works for me. I have tried other (hard)woods, but I haven't found a good reason to move away from the conventional spruce.
    I think compressibility & weight are the most important factors (which will translate into impedance), which may give small differences in sound colour & instrument response. Try testng on your instrument by attaching a small weight to your spruce soundpost, and you'll roughly simulate a heavier maple soundpost, set at exactly the same location.

    Just some comments on misleading statements I see here:

    "i visualize the soundpost as the one point of no vibration, with everything radiating from that nodal point."
    Of course everyone is free to visualise whatever he likes, but in reality of course the soundpost vibrates, as does everything in the instrument when it's being played. Obviously not everything vibrates with the same amplitude, and indeed the amplitude the top's excursion at the location of the soundpost is much smaller than at various other places - it's much stiffer there due to the link with the back.
    And the vibrations from the strings radiate into the instrument mainly from their contact point with the bridge, not from the soundpost. Unless you play the instrument by plucking the soundpost.

    "i don’t believe the soundpost transmits vibrations to the back."
    Again, everyone is free to believe whatever he wants, but of course transmitting vibrations to the back is exactly what the soundpost does in reality (in addition to supporting the top to carry the bridge). Put a (pressure) piezo PU inside the soundpost, and you'll get a very strong (but dreadful) signal. The amplitude of the vibration in excursion is not very big there, but the amplitude of the vibration in force is, so that the amount of power (=force x velocity) transferred is substantial. Via the SP the back is actuated with more or less the same amount of energy as the top, IMO. This is why some luthiers also tune the back.

    I believe the soundpost is the strongest of the mechanisms linking the vibrating top & back, and being a stiff link, it acts as a nodal point for various vibration modes in both top & back.

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