A happy accident needs attention

Discussion in 'Luthier's Corner' started by Hambone, Nov 17, 2005.

  1. As you all know, I'm getting towards the end of the Fairlane project. This is a newer design and there have been a lot of little details that have come up and been resolved along the way.

    This particular version is chambered for weight like I've done in the past and has a great acoustic tone but last night, I got a shock when I was playing around on it after restringing it with the new saddles. I bent over to pick something off the floor and I inadvertantly hit a couple of strings. With my head behind the bass body, it was LOUD - too loud for normal. So I put my ear against that back of the body and played normally. OMG!!! It sounded like the inside of the body was a cathedral and the walls were speakers! There was an incredible amount of volume within the body chambers. In one way, this is precisely what I was trying to achieve with this bridge design - get more coupling between the strings and the body without the insulation of a metal bridge. But I didn't ever expect it to be so loud and incredible sounding being done on one of my chambered designs.

    So now what to do with this newfound characteristic? I probably won't be doing anything with this particular instrument since it's been pretty much spoken for and it's late now as it is. But I'd like to hear opinions (especially from the knowledgable :eyebrow: ) as to what I could do to exploit this in a future instrument. I never intended to make tone chambers or anything like that and I'm not going to pursue tuning the interior of the body. I'd just like to get a feel for how to get some of that great tone out of the body and into an amp - perhaps without using any other pickup? I'm just not up on the latest tech for this type of rig.

    So lemme have it!
  2. Geoff St. Germaine

    Geoff St. Germaine Commercial User

    Aug 31, 2001
    Halifax, Canada
    Owner - St. Germaine Guitars
    Does it do the same thing when you hold it by the neck and play the strings? I've experienced coupling of my basses to a number of things, notably when I've rested them against my hard case. I would say that it is 2 to 3 times more volume just from having the tuners touching the case.
  3. Geoff, it does it looking sideways - that was the surprise!
  4. sounds to me like you need to find a way to put a piezo in the bridge region of this design...

    i don't know how you'd do it with this thing...but perhaps you can experiment with placing the piezos in the bridge blocks that you've made....

    the difficulty would be finding an elegant way of then getting this wired to the electronics cavity...

    another option may be imbedding the pickups under a laminate in the saddle channels...

    you know what 4 separate piezo pickups mean, don't you?
    THAT'S RIGHT....MIDI READY! :hyper: :hyper:
  5. budman

    budman Commercial User

    Oct 7, 2004
    Fredericksburg, TX
    Owner/Builder of LeCompte Electric Bass
    Maybe you could install a small microphone into the chamber(s). It would be isolated so it shouldn't pick up any outside noise. I don't now if anyone makes a small pedal type microphone preamp, but if they do you could rip the guts out and install them in the bass like regular preamp so you would have some sort of control at the bass...maybe.
  6. You know that is one of those things that I've always wondered, why do basses sound so damned good when you have your ear to the body or neck. I mean it's a great piano like almost distorted tone that would be great to hear in the real world. Wouldn't you think if your ear can hear it you'd be able to duplicate it? So far the closest sound to that I've ever heard was my uncle's custom made LED pickup system. Perhaps piezo, but I've never heard one that good even RMC, perhaps lightwave, I always wanted to check one out but no 6'ers.
    I do like the microphone idea, perhaps mounting an old kick mic, oops did I say that out loud? Nevermind, I'm off to experiment with an old AT mic. :)
    Good luck in any case.

  7. how about one of the small microphone systems like Martin uses in their acoustic/electric guitars????

    I'm just worried that the mic tone would sound a bit "boxy"...but, you never know until you try, right?
  8. I wonder if, in these conditions, you could push one of the acoustic guitar mics to good results - always looking for the cheap way out of course ;) I suppose there exists an acoustic bass mic designed for use in the body but I bet they are rare. I'll have to research.

    Piezo's are intriguing because the saddles could be adapted by a monkey...and I'd like to see that.

    Did I hear a question about elegant wiring? :smug: In my dreams, I've toyed with the idea of laying adhesive backed copper foil on the inner surfaces of the chambers. Taking it a step further, I could shield it by using layers of foil and pressure sensitive vinyl to make a flat ribbon that could be adhered along the lining surface. It could terminate at a screw block or something to start dividing up the wiring.
  9. Well great minds think alike huh (see above).

    I could do it as an experiment and not destroy a body by leaving the body unfinished but completing the build. Then I would bore a hole in the end of the bass into the largest chamber. The hole would only be the large enough to pass the mic to get an idea of possibilities. If it's a go, then the mic system is installed onto another premade plug - a larger one designed to be inserted into the hole that has now been enlarge to accept it. Then finish it off. If the mic is crap, then plug the smaller hole and finish as planned and I won't be able to see it, well hardly
  10. budman

    budman Commercial User

    Oct 7, 2004
    Fredericksburg, TX
    Owner/Builder of LeCompte Electric Bass
    I've seen several bluegrass double bass players with these funky looking brackets mounted on the front of their basses hold what appears to be a plain old Shure SM-57 pointed at the bridge. Seems as though that's the prefered method for bluegrass vs. the piezo route that jazz players take. Of course mounting an SM-57 into a chambered solid body, that's a different story.

    Maybe line the chambers with piezo film? :hyper:
  11. Frank Martin

    Frank Martin Bitten by the luthiery bug...

    Oct 8, 2001
    Budapest, Hungary, EU
    Piezo-electric crystals respond to pressure, not vibration.

    DB/cello microphones?
  12. budman

    budman Commercial User

    Oct 7, 2004
    Fredericksburg, TX
    Owner/Builder of LeCompte Electric Bass
    Doesn't vibration exert pressure? Why, I believe it does! I've seen lots of car parts that snapped in half from constant vibration...and a vibrating bass string doesn't cause a constant pressure anyway. You can stick piezo contacts on or under the bridge of a double bass, why not in a chamber? Doesn't Micheal Manring use some wierd piezo system on his Hyperbass?
  13. I think they do respond to vibration. The only thing I have to support that is the bi-directional applications piezo's are used in - shoot a voltage to it to make it vibrate and you've got a tweeter. Likewise, vibrate it at the right frequency and it generates enough voltage to make an arc spark like used in a lighter.

    Unless I've been misinformed all these years. :(
  14. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    piezo's need some amount of pressure to create voltage, if you just stuck a piezo in open air, it wouldn't respond like a mcrophone. And if you just attach it to the wall of one of the chambers you would get some output but it would be very weak and very trebly. That's just from my experience though. One thing you could try, which I have played around with a little bit, is taking two thin flat pieces of wood and sandwiching the piezo between them and screwing this whole assembly to the wall of the chamber. I've found that increasing the pressure on the piezo like this will increase the output and increase the bass response, I've only toyed with it though, and always resorted to the usual under bridge mounting.

    I think the most promising solution is a DB mic like others have suggested, check out this little unit out from K & K.

    http://www.urbbob.com/bassmic.html (bob is a TB'er by the way)

    The real challenge is going to be mounting the mic in a way that it isn't coupled to the bass body in any way. You need some sort of shock proof mounting that will keep the vibrations of the body and the noise from moving the bass around and what not from being transferred directly to the mic, other wise you will get loud noises, uneven frequency response, and other unpleasant results. From my work with piezo's I can tell you that even the way in which the cable touches the body can have an affect on the sound of such a sensitive transducer as a mic or a piezo. Coming up with interesting solutions to these types of problems seems to be one of your specialties though.

  15. Damn! I forgot about Bob Gollihur and his stuff. That might be the ticket.

    The rest of your post is most enlightening, thanx. You've given me a lot to think about. The idea of mounting the mic where it's totally decoupled from the body is going to be a challenge for sure.

    Would there be any use in pursuing the idea of going the opposite way with idea of coupling the mic to the body? By that I mean making the physical connection between them so complete and solid that the lower volume noise is soaked up by the mass of the instrument and the remaining sound is clearer. A variety of increasing the signal to noise ratio, I suppose.
  16. paintandsk8

    paintandsk8 Pushin' my soul through the wire...

    May 12, 2003
    West Lafayette, IN
    Mounting the mic directly coupled to the body will certain create a much different frequency response, attack, etc. Whether that will be for better or worse is beyond me. It is something your going to have to play around with. Like you mentioned before, your best bet is going to be to make up a body that you can try many different things with, whichever methods you try, they are going to take a good deal of tweaking. On my last EUB I actually spent over ten hours trying different methods and tweaking the way I mounted the piezo's before I got a sound that I was happy with. This is something that has not been attempted often, so there isn't alot of info about techniques, so you are just going to have to try anything and everything to you find something that gives you the sound you are looking for. You might talk to Bob too, he probably has a better idea of how a mic is going to react to different environments and different mounting techniques than I do. I've found him to be very helpful with any of my questions.
  17. Suburban


    Jan 15, 2001
    lower mid Sweden
    CAn't find teh brands right now, but just a few weeks ago I saw an ad from a US guitarmaker, pointing out the use of a special kind of mic. In the early '80s, they were simply called "contact pickups". They work by a miniscule mass, that is set in a coil, thus inducing a signal when the surface it's attached to vibrates.

    This post is absolutely to the point and knowledgeable, with one exception: I can't make myself remember the "modern" name of that kind of pup! :crying:
  18. Would that be a "transducer" pickup? I seem to remember one brand that looked like a big nicad battery with an orange wire attached to it. I think it had a 1/8" mini phone plug on it because of it's size.
  19. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    What about those mics that are meant for attaching to walls/drum shields/etc? It's basically a flat rectangle that you can attach to your surface of choice? That might work out well.
  20. teej

    teej Venmo @teej1986 Gold Supporting Member

    Aug 19, 2004
    Sheffield, AL 35660
    F-hole? Let some of that noise out!