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About to make another C-extension; any new ideas/great links?

Discussion in 'Basses [DB]' started by GerardSamija, Jan 13, 2003.

  1. I'm new around here, but did a thorough search of the archives and couldn't come up with more than passing references to C-extensions for doublebasses. I posted a little in a thread about bridge adjusters, but for a slightly better chance at an answer here's my situation in total.

    I made my first C-extension about 6 years ago, for a VSO player. It was a 4-capo type, as he wanted access to a lot of natural harmonics for new music stuff, and the odd older composition requires low pedals. The player had asked for a really solid 'lock' at each semi-tone, so I tried bullet catches. They seem to help a little, the ball bearings being pushed firmly into little detents in the stainless armatures. But I found that the springs 'sang' in sympathy with certain pitches, so an injection of silicon grease was needed. Since then, he's been happy. The long slots in the ebony for tuning the adjusters have never been needed. I'd suggested that these were not really necessary, but I suppose my explanation of the 'rule of the 18th' (actually 1/17.835) inspired insufficient confidence. Add in tapped holes with nylon set screws to make little adjustments to the pressure applied by the leather pads' leading edges, a foot to support the wheel end, in case of knocking into doorways - unpleasantly complicated, not to my tastes. Sorry for the fuzzy pictures; just used a little digital add-on to my Pocket PC to copy a couple of snapshots in incandescent light, for use here.


    Over the next few extensions things simplified. I tried to see just how maintenance-free and accurate I could make them. Nothing earth shaking, but people seemed happy. Getting a big, slack C string not to buzz is the hardest part, with really consistent and solid feeling capos being second. Here's one of those, made last year for another Vancouver player. She's small, hence the dropped nut for a fairly short scale without moving the bridge out of balance on the belly:


    All along though I've felt there must be a better way. Every C-extension is different anyway, so why should they not improve in design, not just execution? Thoughts of hydraulics kept coming to me from players, but I'm not that high tech in the skills department. And levers, springs, cams, they all make me nervous. And I've worked on enough mechanical, piccolo-type extensions to know what a nest of hornets they can be for maintenance. What about using drill rod, little bar stock bent to act as precise capos? A bit of small tubing should make it work, no? And now I see that someone is doing this, but only for the upper capos, not the E. The confines of that region at the nut make the old swinging capo a better choice, apparently. This from the Merchant site:


    I have this guy coming on Wednesday, again. He listened to me think out loud for an hour yesterday, and seems to trust my work from having seen enough in repairs and in his cohorts' C-extensions in the symphony, but he also wants more. He's asking me to experiment on his old Italian, to make a proper C-extension. He's used one from another local luthier for about 10 years, but it's wobbly and the only capo on it is not capable of holding a string for long without buzzing. There's not a lot there to work with, no way to add capos, so it's time for a new one. I am seeking ideas, drawing a blank. Can anyone help me with this? Suggestions, cool stuff you've seen somewhere on the web or even have on your own basses? Pictures of anything out of the mainstream would be helpful perhaps in triggering something in the little grey cells. I've seen Barry's sliding version, and it's not what is needed here. Instead I want to make a 4-capo thing he can blindly reach for and have it respond with little fuzz and effort, both applying and releasing capos. What can you tell me? Thanks in advance for anything at all.
  2. LM Bass

    LM Bass

    Jul 19, 2002
    Vancouver, BC
    Hey Gerard!

    Nice to see you here! I hope you are doing well! Thought I might see my extension there -but I figured out that your question is about the 4 capo thing.
    I saw a Martin bass at Hammond-Ashley last Saturday that looked interesting. They used a very thin metal capo, only about 1/8" diameter or less, with a small nut for the E and D stops. It seemed to work okay on the E (which had a little shelf too), but the D one wasn't functinioning yet. I think this was their shop's design, not T Martin's.

    I'd be happy to send some work your way if you are into it. Let me know via the usual e-mail.

    Talk to you soon,
  3. I have the name and phone number of the person who makes the capos for Bill Merchant. Contact me if you are interested.
  4. Martin Sheridan

    Martin Sheridan

    Jan 4, 2001
    Fort Madison, Iowa
    Bass Maker
    Check out the C extensions we make a KC Strings.
    The are easy to adapt to any bass and do not require drilling or cutting into the scroll.
  5. WOW, Martin, that's some serious brasswork you've got there! I'll study it some, talk to the player, and see what he thinks. I'm a bit leary on the fitting to any configuration of scroll and fingerboard thickness, while allowing for future fingerboard replacements and such... but your design probably takes such things into account. Thank you very much for the images. Good to have for comparison.
    Anyone else?
  6. I've seen the KC Strings C extension, and it is indeed a beautiful piece of work. Unfortunately, what makes it beautiful is it's biggest downfall. It is very heavy and that has to make a major change in the resonance frequency of the neck (B0). Also, I understand that they are prone to rattle (brass against brass) when playing pizz.
  7. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    Martin- did you design that KC Strings Extension?
  8. Martin Sheridan

    Martin Sheridan

    Jan 4, 2001
    Fort Madison, Iowa
    Bass Maker
    The KC C extension was designed by Yakov Izrailev who is a Russian emigre and engineer, and who works with us here in the shop. He also designed the 36:1 brass bass gears we use. Misha Krutz who is one of the owners of the shop and a bassist with the KC Symphony gave his ideas, and I had a little imput into the tuning gears.
    The C extension is not brass on brass, both styles have ebony with lizard skin that comes down on the string. The top part of the extension, or fingerboard extension, is ebony. They are heavier than all wood, but all of the players who've had them put on say they've added to the sound. We recently put one on for Bob Anderson, first chair of the New Orleans symphony,and as a result 3 other players came in within a few weeks wanting them on their basses. They all had the same positive comments. I used them before I stated working here, they're easy to put on compared to making one by yourself from scratch and do not buzz; all things I liked about them then and now. Tracy Rosenkrans and her husband who are professionals in Tucson have them, and Jay Foote a student at the University of Iowa, just to name three more.
  9. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    Is that Bob Anderson or Dave Anderson? Just curious. What size bass was it?
  10. Martin Sheridan

    Martin Sheridan

    Jan 4, 2001
    Fort Madison, Iowa
    Bass Maker
    Dave Anderson, and a big mama Prescott.
    Bob Anderson was or is with the North Carolina Symphony.
  11. Martin,
    I find it interesting that adding a two pound brass extension the the neck of a bass has made the basses sound better. My experience has shown that it only takes a few ounces of weight added to the neck to move the resonance frequency of the neck. Assuming that the neck had previously been properly matched closely to the resonance frequency of the body, adding weight can only change the neck resonance (B0) further from the body resonance frequency (A0). The extension I have on my personal instrument has a total weigh of under 8 ounces. Until I re-tuned the neck/fingerboad of my bass after installing this 8 oz extension, my instrument did not play at all like it previously had. I have seen this same condition repeated when heavier tuning machines have been added and of course when a new heavy fingerboard is installed. I've seen a few cases where adding a small amount of weight has improved the sound, But that was a few ounces not pounds.

    The rattling that I was refering to was not about where the string is held, but rather in the sliding capo mechanism (which I believe is brass to brass). I doubt if arco would set up this type of rattling. I was specically referring to pizz.

    The KC String C extension definately offers the player and excellent option for adding an extension to an instrument without the neccessity of drilling a hole through the top of the scroll or otherwise visibly damaging a fine instrument. If this is the paramount concern, then the KC Strings extention is the perfect choice. However, it does not add to the structural rigidity in the same way as when a custom made wood extension is fitted. Just as carrying excess weight on your body results in less speed, excess weight on a bass reduces sound. That is one reason I'm not to crazy about solid ebony extensions either!
  12. I received an email this evening from my good friend Anton Krutz, who is the master luthier and one of the owners of KC Strings. Anton informed me that I was incorrect when I stated that their fingered C extension has brass parts that may rattle. He further informed me that there are not ANY brass parts touching each other in the extension. That being the case, I apologise to the folks at KC Strings. Like the luthiers on this forum, Anton and I occationally disagree. He does not agree with me when it comes to the matter of weight killing sound. So on this matter, we agree that we disagree. KC Strings is one of the premier shops in the country and my previous comments about their extension were not meant to cast any doubts as to the quality of either their shop or the products they sell.
  13. Chris Fitzgerald

    Chris Fitzgerald Student of Life Staff Member Administrator

    Oct 19, 2000
    Louisville, KY
    Was it a 4/4? If so, that's the same guy who used to teach here at the U. Great player, great dude, great hang, and a sense of humor to die for.
  14. Martin Sheridan

    Martin Sheridan

    Jan 4, 2001
    Fort Madison, Iowa
    Bass Maker
    The Prescott was more of a 7/8, but very heavy.

    I understand Bob's concern about weight. I would not put a ten pound c-clamp on a bass and expect an improvement, but I'm reporting what I have heard myself, and the players comments about the extension giving their basses more volume.
  15. How about a 5 pound c-clamp or a 3 pound c-clamp? I'm not buying it. As I explained to Anton, almost any change to the weight of the neck assemble changes the resonance frequency of the neck. I don't care if it is Anton's C extension or mine. Any change in the weight of the neck will change the neck resonance frequency to some degree. The more weight, the more change. Significantly reducing the weight of the neck will also change the B0. The only way I could see ANY extension helping the sound is if the instrument was terribly A0/B0 mismatched before hand and the added weight of the extension just happened to make the resonance frequency of the neck (B0) come closer to matching the resonance frequency of the body (A0).

    Now for the other side of the story -
    There is no reason for the A0 and B0 to remain mismatched. I have sent Anton a copy of my 1997 MVA journal paper on matching A0/B0 in basses and have offered assistance in trying the method on one (or more) of your new basses. As I told Anton, if adding the extension has helped the sound by adding weight, then correcting any A0/B0 match can only make it better.
  16. Sam Sherry

    Sam Sherry Inadvertent Microtonalist Supporting Member

    Sep 26, 2001
    Portland, ME
    Euphonic Audio "Player"
    Do you hear a difference between plate machines and singles?
  17. Given no other considerations - No.
  18. nicklloyd

    nicklloyd Supporting Member/Luthier

    Jan 27, 2002
    Cincinnati, Ohio
    Back to extension ideas-
    I heard about a Montreal luthier that carved the extension as part of the scroll/pegbox. I forget this guy's name...? I know you asked for extensions on preexisting scrolls, Girard, but this sounds too cool. and difficult.
  19. I'm pretty sure that Bob Ross in Denver has done something like that too. I don't think Bob has a web page now, but I know we have a member of this forum that has a Bob Ross bass. Maybe he would care to respond.
  20. You mean sort of like this?
    I drew this about 2 years ago. Meant to get the bass done, mostly, then with the roughed-out built-in extension I'd figure out the details. It's one of the grey areas that has got in the way of my continuing with the project. I don't like building failures, nor even partial successes. Since my patience for doing any one thing repeatedly is about zero, I like to get it right the first time, insofar as that is reasonable. Of course, I know, one improves rapidly with actually making the experiments and then seeing what needs improving. But I am also dealing with a frugality issue, both in terms of a desire not to waste wood, and just being broke for about the past 41 years. Mistakes in bassmaking cost a few thousand dollars in materials and a huge bunch of time. I can't afford either, with rent and other bills to pay.
    So whining taken care of, what do you all think of this for a new bass? Since I drew it I have changed a few ideas, thinking it'd be better to have a more organic flow, though perhaps not quite so curvy and soft as that Kelischek in cherrywood. The bass outline itself is somewhat agressively pointy. The C's are very long, with corners arcing inwards to a degree impossible to maintain should they come closer to the bowing plane. The upper bouts are rather small, the lower huge, relatively, and the upper ribs twist back to allow for a 3" shorter upper back than belly. Rib height is thickest at the lower corners, with a 1 1/2" drop as it nears the neck, and a 1/2" drop towards the endpin, using a constantly curved gluing plane around the back edge. Belly lies flat. Arch is low, as the inner back curve more than makes up for lack of a steeply pitched arch.
    All in all, an odd little 3/4 bass, with a projected scale of 41 1/2". The girl who used to want it, before a pop career and my delays put her off, is very small. I developed it according to her low shoulder height, but in the intervening time I've had many comments from bigger bassists who are keenly interested in a smaller bass for many reasons. I think the volume internally should approach that of a Kay, perhaps 5% less. And with careful plate tuning I see no reason it should howl when needed. The spruce is a glorious piece, something quite extraordinarily perfect and responsive.
    An extended C will probably be 'pushing it' for a smaller bass like this, but we'll see. I mean to pay a lot of special attention to designing a bridge to maximize output, with a bar set a little outboard for greater belly movement at lower frequencies (with matching post position of course). I want also to make certain that I have a decent and long lasting capo design before attacking the scroll wood with a saw. Hard to stomach the idea of gluing bits on to make up for lack of foresight.
    Any comments on such a design are very welcome! Of course, my current problem is rather different. No opportunities for teflon inserts to the scroll on this old Italian, not grafting in maple to stiffen the wobbly old thing. I have to make the scroll stiffer, without sacrificing a shaving of maple anywhere. Anyone I caught sawing bits out of old scrolls I'd probably slap, risking the arrest. There are few worse crimes in luthiery these days that that, though I suppose some contenders in the krazy glue department.

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