1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  

Carbon Fiber Soundposts- the techno nerd's report from Oberlin

Discussion in 'Setup & Repair [DB]' started by james condino, Jun 23, 2012.

  1. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc
    In the past three + decades, I've attended a LOT of luthier related "nerdfests".... as a participant in the crowd, as a student, and as someone on the payroll giving workshops throughout the week. Given how obscure our profession is, having 20+ bass builders in the same room is equivalent to having about 4000 guitar builders present. There were some fantastic people from many different countries and continents present and the exchange of information was wonderful; by the second day I felt as though I had already made it worth my time and money. Over the next few weeks, I'll be giving a few reports on some of the "happeninz" that you probably won't hear about.... As a TB disclaimer, I've got NO financial interest in this and am offering it solely in terms of increasing global bass nerdiness for anyone interested.

    During the middle of one the workshops, I happened to be goofing off in the back of the classroom with James Hamm and his buddy JB. JB happened to be JB Allred, of Allred carbon fiber / Dragon plate/ and such. Jim and JB are pretty tight, so I was the outsider kind of eavesdropping checking out the latest high tech carbon goods JB had brought along. I was familiar with Jim, having attended a couple of his workshops last year at the Guild of American Luthiers conventions and knew they were into some interesting stuff. Having wasted a lot of years in engineering school,I instantly invited myself into the conversation, as JB was showing off his new carbon neck "stiffening systems" and pulled out a handful of carbon tubes suggesting they might make interesting soundposts.

    That was all I needed. I've been wanting to try carbon fiber soundposts for several years. Without asking, I grabbed one from JB, walked over to my workbench and proceeded to chop it up and install it in my bass. As a side note, although I was primarily looking out for myself, it also made good sense. My bass was the only one present with a trapdoor that made soundpost adjustments a very easy and efficient task. In about 10 minutes, I had sized up his tube, added spruce end caps, and installed it. Don't get too nerdy worked up about the position or placement- I've been moving it around almost daily and the current position is the one that worked the best for the room I was in for rehearsal this afternoon. You can see the trapdoor on the left of the photos that allows quick and easy adjustments. You can also see the "fuzzy" bass bar, results from allowing a luthier to have instant access to the insides of their own bass and be constantly whittling away and mucking about with the insides...

    Seth Kimmel and I then spent about 45 minutes adjusting and trying different locations until we found the one that seemed to work the best. JB came up and asked us what our initial impression was. Seth and I both agreed- "Well, there seems to be nothing lost overall and an audible amount gained in the high end and the low end seemed to be smoothed out a bit..." With that we made him a promise- we'll stay up until dawn giving it the best effort we can with the help of the rest of the late night crowd and give it and honest workout.

    True to our promise, we enlisted the help of several others and proceeded to stay up until just before 5am that night/ moring and put it through the test!

    I've had it in for about a week and a half now, played several gigs with it, and my general impression is similar- nothing lost, but a little bit gained throughout the spectrum. The general character of the bass was the same, but certain areas of tone seemed to "pop" a bit more and cut through in the mix. On this bass, depending upon the location of the soundpost, the C/D notes on the G string get a HUGE increase in volume, along with more moderate success throughout the range. I have not noticed any new wolftones and the results seem similar for both arco and pitz. So far I have not weighed it on a scale to see how the density compares to spruce, but on that particular bass, I've tried about five different types of spruce and cedar soundposts. I don't have any plans to remove it and would encourage anyone curious or interested in the idea to give it a try. I don't have the specs for the wall thickness- as soon as I cut it down and glued the caps on, everything was sealed up. Give JB a call and they'll be able to give you the details.

    As a whole, this type of thing was happening all day long for the entire week in several different rooms at the Oberlin workshops. If I had a little more time, I would have liked to have done a modal analysis of this one compared to the spruce soundpost. The reality was that I didn't need to- my ears told me to keep this one in for a while.....:):):) Your results and mileage may vary from these.....

    Thanks again to everyone who helped put the Oberlin workshops together! Stay tuned for the next reports on the "Magic Probe" digital thickness guage....



  2. Jazzdogg

    Jazzdogg Less barking, more wagging!

    Jul 29, 2006
    San Diego, CA
    Great report, as usual! Thanks!

    I'm interested in installing a trap door in the C-bout of my Goetz plywood bass. Reviewing your previous posts has been immensely helpful. :)
  3. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc

    I'd approach that with a bit of caution. Adding a trapdoor to a new bass build may be considered innovative; doing the same to an older existing bass might get you a reputation as a "bass butcher " or worse that might not be what you are looking for...

    Checkout Matthew's thread about adding a door to a New Standard bass. My next new build will be similar to his oval door- nice, simple, and very functional with the magnets.

  4. jonas


    Dec 9, 2003
    Frankfurt am Main/Germany
    Kontrabass-Atelier, Lando Music (Germany), "Das Kontrabass-Buch"
    Interesting project. I wonder how to install a carbon rod without a door.
  5. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc
    The same way you install any other soundpost; 'folks have been doing it just fine for hundreds of years.....
  6. jonas


    Dec 9, 2003
    Frankfurt am Main/Germany
    Kontrabass-Atelier, Lando Music (Germany), "Das Kontrabass-Buch"
    but does the soundpost setter hold a *tube* firmly? I guess that it will sliding off very easily … but that's just a guess, haven't tried it. Looking forward to read more about it!
  7. james condino

    james condino Spruce dork Supporting Member Commercial User

    Sep 30, 2007
    asheville, nc
    Hey Jonas, 'my apologies.

    That makes a lot more sense. I don't use a traditional soundpost setter when I go in through the f holes on the top plate. I use a couple of custom made ones that are like giant versions of the little violin scissors type- a sort of big, flat, multi-angled plier effect that allows me to get a very firm grip around the post, set it exactly where I want it, and also have the ability to rotate the post and make sure it fits snug in all directions very easily and quick, with no "stabbing" required to get it in position or aligned. They are so much a part of my daily work that I sometimes forget about the other methods.That is another reason why it made sense to use my bass. I believe the current issue of American Lutherie has some detailed photos of these tools- if not then they will be in the upcoming issue; I always seem to be the last guy to get the final copy in print.....:meh:

    I think you could install one of these without too much hassle- maybe a few minutes more creativity. The spruce caps keep from damaging the insides of the bass and allow some room for adjusting the length. Some of my customers amaze me with their low tech ingenuity for resetting a fallen soundpost when they are out at a remote location gig and need to get it back in place.

  8. Heifetzbass

    Heifetzbass Commercial User

    Feb 6, 2004
    Upstate, SC
    Owner, Gencarelli Bass Works and Fine String Instruments, LLC.
    James truly made quick work of that post! It was cool to listen as they worked it over.

    I am still working on my Laborie experiment with the units from New Harmony Music. It has Carbon fiber fittings and a cf rod. I am working on doing some testing comparing the cf to the wooden dowels of various species. I will have a friend in town that can help me with recording and analyzing.

    BTW- James, did you get my email last week?

  9. 360guy


    Apr 28, 2006
    Lansing, MI USA
    James, I was delighted to have worked next to you at Oberlin. I am humbled by your talent. Your insight and innovative approaches are a great source of inspiration for me.

    And I was thinking of working with some carbon fiber in the bridge area but then I read this posting another site:

    "As an aviation safety officer, I was taught to be VERY CAREFUL around crashes with airplanes that had carbon fiber parts, as the strands of fiber stuff could get into you, and you can't get them out. Crash scenes are first sprayed with something to encapsulate the stuff, then you can be around the site safely.

    I would think machining the stuff might free up the fibers nearly the same? But of course I've seen knife handles made out of carbon graphite, so I don't really know, but it's worth looking into further if you're not sure either!"

    I have no desire to be a fly in the ointment. I only want to see us all avoid health problems in the future.

    Btw...I'm working on the DVD. Probably get your copy when the snow starts flying ( sometime before your American Luthier summer issue) but the memories will be vintage by then, huh?
  10. Matthew Tucker

    Matthew Tucker Commercial User

    Aug 21, 2002
    Sydney, Australia
    Owner: Bresque Basses, Sydney Basses and Cellos
    call me old school but I think I'll stick with the cheap as chips wooden version until someone writes "Wow! Knocked out by the difference! Every single time!" :D
  11. I've fitted a 16mm solid CF sound post to my bass which although slightly heavier than the old spruce post is significantly stiffer. I'd agree that there's an improvement in terms of 'tautness' of tone. No, it's not a huge night and day difference (are there really any of those left to discover?), but it's there if you're happy to put the effort into shaping the ends (it's a LOT more work than spruce!). No, you can't use a normal SP setting tool as you can't drive the blade into the rod, so I use thick (~4mm) braided nylon cord 'tied' in a lark's head knot (see http://stonebrashcreative.com/MacrameTutorial.html) around and near the belly-end of the post, with the ends of the cord each poking out of its own f-hole; pull the cord tight and the shape of the knot holds the post in an upright position (I usually tie the loose ends together on the belly with the string pulled taut to hold it in position). Pulling on either end of the cord allows sideways positioning of the post and sliding it up and down the f-holes allows vertical positioning. I use a carving fork and gentle taps with my long handled viewing mirror for precise positioning. I also wrap some masking tape around the post and mark the 3 & 9 o'clock positions in relation to the orientation of the end chamfers, which acts like the mark that the soundpost setting tool leaves in a wooden post to set the rotational alignment of the chamfers to the belly. Works like a charm and the lark's head knot is easily loosened for the cord to be removed from the post.
  12. George700DL


    Jan 9, 2009
    lark's head... good option. i use a slipknot on my sp, and leave the string inside the bass. it's never a problem to grab it when i need to. this is a spruce soundpost, by the way, but i never felt the need to stab it with a standard tool, when there are easier options.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.