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Bass Tuning

Discussion in 'Basses [DB]' started by Martin Sheridan, Jan 20, 2003.


  1. Martin Sheridan

    Martin Sheridan

    Jan 4, 2001
    Fort Madison, Iowa
    Bass Maker
    Bob Branstetter brought up the interesting topic in another thread of what I'll call bass tuning. I'd like to see some discussion of this relating to tap tones for the top, back, resonant frequencies, and other related topics.
     
  2. Damon Rondeau

    Damon Rondeau Journeyman Clam Artist Supporting Member

    Nov 19, 2002
    Winnipeg, baby
    Hey, as a learning bystander, I'll second that call.

    I'd even buy the beer if I could.
     
  3. Okay.... to kick it off just a little:
    - Carleen M. Hutchins and Fred Saunders did a whack of experiments going back to over 40 years ago, and she's worked on them a lot since as a practical experimenter. One of their biggest 'discoveries' was that in general, a belly main resonance ought to be about 1/2 tone lower than that of the mated back. There are a few modes to worry about, but if these main 'eigenmodes' are so related, chances are a lot better the instrument will sound well.
    - Bellies in general are very close to one thickness throughout, varying mainly from one instrument to the next for reasons of individual plank stiffness. Some extra thickness is sometimes used in the area of the soundpost, and a little less is often left in the 'lungs, or the outer upper and lower areas, with more being left in the middle or 'spine', sometimes... Backs, on the other hand, tend usually to be thickest in the middle, with various patterns of thinning outwards, sometime in a peanut shape, sometimes in circles, and often a combination of both.
    - 'Tuning' is accomplished by carving away wood from highly vibrating areas to speed up occilation, or weakening other areas to increase flexibility while leaving more mass in the more vibratory regions. Lots of room here for individual figuring out, experiments, and leaps of understanding. But the Journal of the Catgut Acoustical Society is a great place to start. Avoid the heavily mathematical bits, unless so inclined.
    - Gluing together with the ribs sort of tosses any particular pitches out the window, making it apparent that these activities are more to do with establishing balance than supporting directly any particular resonance in a planned way.
    - Air volume and f-hole surface area are both also critical in producing desirable effects in 'brightness' or 'darkness' of tone, volume potential, 'projection'... Lots of variables to think about here, too.
    And yes, some of us 'tune' fingerboards. I have not yet joined those ranks, but Bob's article is fascinating, and I'm trying to wrap my brain around all the nuances. Never know, I could incorporate something. But as for electronic measuring devices in luthiery, nah. I don't wanna go there. It'd have to be blowing across an f-hole and tapping a fingerboard and neck, to make me happy. Haven't tried those seriously yet. Probably wouldn't work well that way either, but maybe.
     
  4. She and hundreds of interested members of the Catgut Acoustical Society.

    One of their biggest 'discoveries' was that in general, a belly main resonance ought to be about 1/2 tone lower than that of the mated back. There are a few modes to worry about, but if these main 'eigenmodes' are so related, chances are a lot better the instrument will sound well.

    I believe what she/CAS said (in early tests) was that good sounding violins usually were about 1/2 tone different. Later research on all instruments showed it was the relationships of the major modes that was most important, not the pitch difference.

    - Bellies in general are very close to one thickness throughout, varying mainly from one instrument to the next for reasons of individual plank stiffness. Some extra thickness is sometimes used in the area of the soundpost, and a little less is often left in the 'lungs, or the outer upper and lower areas, with more being left in the middle or 'spine', sometimes... Backs, on the other hand, tend usually to be thickest in the middle, with various patterns of thinning outwards, sometime in a peanut shape, sometimes in circles, and often a combination of both.

    I don't think you can generalize about the tops being made uniform thinkness. I was taught that both the top and back are more or less tapered from a thick center area to thinner edges as in a bell. I've seen excellent instruments made both ways. I do however, think it is more difficult (but certainly not impossible) to accomplish mode tuning with a uniformly thick top.

    - 'Tuning' is accomplished by carving away wood from highly vibrating areas to speed up occilation, or weakening other areas to increase flexibility while leaving more mass in the more vibratory regions. Lots of room here for individual figuring out, experiments, and leaps of understanding. But the Journal of the Catgut Acoustical Society is a great place to start. Avoid the heavily mathematical bits, unless so inclined..

    Agreed, but I think of tuning plates in terms of mode matching the plates. I also highly recommend the Catgut Acoustical Society as a great place to gain further knowledge. A lot of it tends to be theoretical, but there's been a lot of very practical research done (and still being done) that gives us more clues to making that great instrument we all strive for. It certainly is not the only place to learn, but there have been a lot of very smart people working on this for the past 50 years or so that have been eager to share their knowledge.

    Finally, to respond to Martin's original questions. I don't look for any particural taps tones when I make a top or back. I know many good makers (mostly violin makers) that will insist on a particular tap tone on the plates, but it's probably a lot easier to hear the tap tones on a violin than it is on a bass and I've never found it particularly helpful for me. I don't think you have much control over what the resonance frequencies are going to end up when are making a bass. The main body resonance (A0) is what ever it happens to be for that particular internal body volume and f hole size. You can't really change either by the time you get to the point where you can measure it. No one has ever shown that one body resonance frequency was any better than another. The best you can do is to adjust those other resonances, such as the neck assembly resonance, to match that of the body resonance.
     
  5. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    I'm with Mr. B on this. I think tuning to a specific note is a waste of time/effort. When I do my graduating or regraduating, I listen for a certain "Thunk" with both depth and sustain. From experience, I know when it's right. The back should certainly have a different sound than the top--it's much more dense. And I'll vary the sound of the tapped tables depending on what kind of sound I'm after from that particular bass. I'd like to see discussed whether other makers tap their top plates with or without the f-holes cut. I do it with the holes cut and again with the bass bar on.
     
  6. Although I don't use tap tones the way you do Arnold, I do check my eigenmodes before both the f holes and the bass bar are fitted and again after. The before check is mainly to give me a reference point to shoot for when trimming the bar. Same idea, just a different way of getting there.
     
  7. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    Originally posted by Bob Branstetter :
    Although I don't use tap tones the way you do Arnold, I do check my eigenmodes before both the f holes and the bass bar are fitted and again after.

    What the heck is an EIGENMODE?!?!?!?!?!?!?!?
     
  8. Eigenmode are the node pattens of vibration that occur on plates when a plate is vibrated a particular frequency. The eigenmodes or simply modes are labeled 1,2,3,4,5 etc. The number one mode is the first to occur (at the lowest frequecy). The number two the second and so on. Each nodal pattens of each mode are very different. The existance of eigenmodes in violin plates was first discovered in 1830 by Felix Savart, a physician and physicist . Members of the Catgut Acoustical Society developed a method to use mode patterns while making stringed instruments.
    Here's a website that does a better job of explaining how eigenmodes as related to violin making.

    http://vitagrad.sch2.net/physics/page1.html
     
  9. Damon Rondeau

    Damon Rondeau Journeyman Clam Artist Supporting Member

    Nov 19, 2002
    Winnipeg, baby
    ... and the concept of an "eigenvalue" comes to us from mathematics. If any of you have been unlucky enough to mess with matrix manipulation, you'll remember them as latent roots.

    Think of them as something essential that's left over after boiling down a bunch of data and relationships.

    So, here I'll define a German word for Mr. Schnitzer (hoo boy, I'm taking risks today): "eigen" can have the sense of "inherent in". By the way, Arnold, how many of them out there know how appropriate your name is to your profession? ("Schnitzer" means "carver" in German.)

    I post this not to show how smart I am (I think it shows how unlucky I've been in the past), but to show that all this acoustical research is grounded in very respectable physics and mathematics.
     
  10. Well, I guess that explains why he makes such good instruments. ;)
     
  11. Jeff Bollbach

    Jeff Bollbach Jeff Bollbach Luthier, Inc.

    Dec 12, 2001
    freeport, ny
    Yet this statement appears suspiciously intelligent.....I question your motives Damon.
     
  12. Damon Rondeau

    Damon Rondeau Journeyman Clam Artist Supporting Member

    Nov 19, 2002
    Winnipeg, baby
    Is it intelligent to spend 10 years of your life doing something you're good at but you despise? You tell me...

    I'm feeling smarter everyday with music as my main focus in life again.
     
  13. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

    Sep 26, 2001
    Portland, ME
    Euphonic Audio "Player"
    Every parent who has worked to put the food on the table has wrestled with this question. I suspect for most the answer is, "No, but it doesn't matter. I do the work."

    There are points in every month when I am happy to be a lawyer. There are points in every week when I detest it. If I'm on a bad gig, it can be more work than being a lawyer.
     
  14. Damon Rondeau

    Damon Rondeau Journeyman Clam Artist Supporting Member

    Nov 19, 2002
    Winnipeg, baby
    I understand exactly what you're saying, Samuel. I'm puttin' food on the table for my two little ones and I'm proud of it.

    I hate to get heavy here, but you gotta look after that happiness thing. From somewhere out of the blue it seemed to me, two years ago I found myself clinically depressed. I was completely shut down emotionally and angry at the entire world. I finally knew I had a problem when practically everyone was p*ssed at me and I couldn't get out of bed at all.

    This from a guy who you would never have suspected was susceptible to such things, but here I am, confessin' on a public board. It happens real, real slow and you won't realize it's going on.

    If it doesn't kill you it will make you stronger. I'm better now and getting better every day. It's an attitude thing, but I had to change my thinking to change my attitude. Biggest change? I put myself into the equation now. Works better that way.

    Figure out what turns your crank, and then do whatever it takes to crank it, taking care of business at the same time.

    Public confessional is over now.

    And don't let this little confessional put a stop to this thread!
     
  15. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    it's multi-reply thread time...

    Samuel- what kind of law?

    Arnold- does your German heritage inhibit your sense of humor?

    Tap tuning- I learnt (love that non-word) to flex more than tap. Flexing different parts of the top helps pinpoint where the wood wants to end up, graduationally speaking. I'm all for different ways of making basses. But, the end result is what matters. Ever checked out Ed Campbell's instruments?
     
  16. Is this a trend in violin making? There are some violin makers 'round here that insist that tap tuning is near useless and rely on plate stiffness, contour, and graduation.
     
  17. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
     
  18. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY

    Actually, it only appears that way. While it's true that THICKLARD looks down his nose at most folks he meets, it's mostly just because he's very tall. And while I've spied neither fish nor chip on any of my trips to his shop, I have noticed the way he sticks out his right pinky finger while drinking coffee or holding a soundpost, so you may not be too far off regarding his diet.
     
  19. Jeff Bollbach

    Jeff Bollbach Jeff Bollbach Luthier, Inc.

    Dec 12, 2001
    freeport, ny
    Not a trend at all. This topic has been debated for centuries. With good and bad fiddles coming from both camps. Each maker has to blend his/her own percent of science and alchemy. Some lean more towards science and some alchemy. Personally, I don't rely on tap pitches, I just plane away untill running my hand over the contours of the plate gives me luthier wood. Then I know its ready for gluing.
     
  20. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    well, THANK YOU for acknowledging my Welsh ancestry. it's the subtle difference that always interests the overextended.
    well, "Martini" Sheridan started this thing; where are ya, bud? assembling email lists on KC Strings dime? what's your opinion of tap tuning?