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Thread: Improper intonation and Ebony bridge 'blank'?

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    Default Improper intonation and Ebony bridge 'blank'?

    Hi - I've been tinkering with a Kentucky 675 that I picked up recently, and I noticed that the intonation is off on the D string pairs, while the rest are fine. I got the idea of making a custom bridge top (ie. the top part of the bridge) with specific string compensation in order to correct this. I am hoping the community can provide some feedback on a couple questions here:
    • Does this sound like a sensible solution (ie. have i overlooked any obvious yet simpler remedy to resolve the intonation issue)?
    • Where can I buy ebony blanks from which I can fashion the top part of the bridge?
    • Is it possible to buy non-compensated, adjustable mandolin bridge?


    Thanks in advance.

  2. #2
    Registered User sunburst's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Is the D noting sharp or flat?
    If it's sharp, the fix is easy. Using a needle file, file away material from the front edge of the bridge where the A strings rest until they fret in tune.
    If the D strings are flat, the fix is about the same, but you must place the bridge so that the D is in tune and file the rest of the bridge until the others are in tune also.
    (Actually, you can probably set the bridge so that the E and D are in tune and only have to file the G and A.)

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    Café habitué Paul Hostetter's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    1) the boilerplate layout of intonation setbacks is just that: pretty good for most mandolins. I believe it's focused on J-74s on a 13.9" scale, which is probably what you have. I often teak those points of contact, but usually for folks who have a firm and permanent idea of what strings they're going to use, including the basic action and so forth.

    2) No one sells ebony blanks. You eiether have to make your own from scratch or, as I would recommend, glue little bits of wood to an existeing saddle which will enable you to reposition that D string where you think it needs to be. Just do that first: clean up the surface, glue on a bit of ebony, and recut the saddle for that one course. If you prep the surfaces, it'll sound fine and will not pop.

    3) Again, no, you either make your own from scratch or you make your own from scratch. Which is possibly worth doing once you've established a better layout for intonation than what a standard bridge affords you, by simply amending an existing commercial bridge. Remember, you can always change it back.

    For what it's worth, age and condition and gauge of string are more variable than you might wish. You may find yourself working feverishly to correct a bridge for one set of strings only to find it completely wrong the next time you change strings.
    .
    ph

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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Quote Originally Posted by sunburst View Post
    Is the D noting sharp or flat?
    If it's sharp, the fix is easy. Using a needle file, file away material from the front edge of the bridge where the A strings rest until they fret in tune.
    The D is sharp. Do you mean file some of the material away on the front of the bridge where the D strings are, in order to bring the point of contact further back?

    Quote Originally Posted by Paul Hostetter View Post
    1) the boilerplate layout of intonation setbacks is just that: pretty good for most mandolins. I believe it's focused on J-74s on a 13.9" scale, which is probably what you have. I often teak those points of contact, but usually for folks who have a firm and permanent idea of what strings they're going to use, including the basic action and so forth.
    I am indeed using J74s and have been on most of the other mandolins I play. I am still going back and forth on the action to see what the difference it makes in the tone, but mostly I've settled on 4/64" on the G and 3/64" on the high E. It actually did not occur to me that I can glue some extra ebony wood to the bridge where the D strings are, and then reshape the top. Since I have some ebony scraps lying around from a guitar fingerboard, I will do just that as a start to see how far I can get.

    Incidentally, after I posted my initial message, I went online and started looking for a good source of ebony as there isn't a readily available source locally for me. StewMac sells a ebony blank for guitar bridge that seems like a good candidate if I decide to make one from scratch. Grizzly.com also sells a similar, albeit slightly thicker (2.5" instead of 2") blank that will work as well.

  5. #5
    Registered User sunburst's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Quote Originally Posted by barrangatan View Post
    The D is sharp. Do you mean file some of the material away on the front of the bridge where the D strings are, in order to bring the point of contact further back?
    Yes.

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    Default Re: Improper intonation and Ebony bridge 'blank'?

    "For what it's worth, age and condition and gauge of string are more variable than you might wish. You may find yourself working feverishly to correct a bridge for one set of strings only to find it completely wrong the next time you change strings."

    What a happy thought............ its sad, but true!!
    No such thing as a dead mandolin!

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    Registered User Ivan Kelsall's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    I'm not trying to knock your enthusiasm here re.making your own bridge saddle,but why not simply buy a top quality bridge from Cumberland Acoustics & fit that. If you wanted a non-compensated bridge,Steve would most likely make you one to your exact requirements. I had a similar problem with a Mandolin i once owned,i fitted a CA bridge & it solved the intonation problem perfectly,
    Ivan
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    Registered User sunburst's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Steve has sent me unfinished bridge tops before, to cut to my own specs, but now he cuts them to my specs for me (Thanks Steve!).
    I still adjust intonation on each bridge though. They are never exactly in tune right off the machine, and 'perfect' intonation is too much to expect from a compensated bridge because of the differences in string sets, string age and condition, action height, etc.. The procedure of filing the front edge of the bridge, that I outlined above, is a process I go through during nearly every mandolin set up I do.

  9. #9

    Default Re: Improper intonation and Ebony bridge 'blank'?

    So I take it a common experience might be to dial in a new instrument (to me) fairly close with one particular set of strings and action setting, play it in for a while and adjust string gauge and/or action slightly to taste, and then perhaps tweak the top of the bridge in the manner John suggests if one or two courses fail to intonate properly after those changes. Is that how it often works out?

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    Café habitué Paul Hostetter's Avatar
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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Yep.
    .
    ph

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    Default Re: Improper intonation and Ebony bridge 'blank'?

    Quote Originally Posted by Ivan Kelsall View Post
    I'm not trying to knock your enthusiasm here re.making your own bridge saddle,but why not simply buy a top quality bridge from Cumberland Acoustics & fit that.
    Ivan - no knocking at all. In fact, if this little experiment (ie. reworking the current bridge by gluing a little bit of extra wood) fails to pan out, I will most likely email Steve and ask him to send me one of his CA bridges with only rudimentary compensation done on the top, so I can 'dial it in' after it is fitted on my mandolin. Thanks for the suggestion.

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    Default Re: Improper intonation and Ebony bridge 'blank'?

    All thanks to you Paul and John for the insights and recommendations. I'll post back later on how the experiment pans out.

    Paul - love the fret wire article you have on your site.

    John - I'm reading your article on turning a radius fretboard into a flat one. Good stuff.

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    Default Re: Improper intonation and Ebony bridge 'blank'?

    I spent some time last night and superglued some ebony scraps to the bridge, and then reworked the compensation, and it definitely improve the intonation by a lot. Here's a picture of what the new bridge looks like. You'll notice that the D strings aren't the only ones I've adjusted. Since I was already at it, I also made some minor changes to the G strings and A strings. And even though I tried to measure the amount of adjustment I needed to make on each pair before, I invariably ended up filing just a tad too aggressively, and the edges are very rough from the rework. But appearance aside, I am quite happy with the result, and am glad to have a far more correctly intonated instrument to play with.

    Thanks again to all for your kind assistance and advice.

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