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Thread: Mandocello buzz: neck relief and string action

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    Certified! Bernie Daniel's Avatar
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    Default Mandocello buzz: neck relief and string action

    I know that we have had strings on this topic before but I wanted to focus in bit on some specifics.

    I spend a lot of my time trying to make pleasing sounds on a mandocello -- mostly I play on one that was converted from a jumbo body arch top guitar.

    1) The issue: I have been experiencing an annoying amount of buzzing with this instrument. The buzzing occurs most often on sustained chords becoming noticeable as the sound volume begins to “die off”. For example, a chord formation like 0553 (= C major) or one string over 5530 (= F major) the chord sounds great as I strike it but as the sound dies down a profound buzzing occurs and dominates.

    I can stop this buzz instantly by slightly releasing finger pressure on the strings – but if I instantly hammer back on the buzzing sound returns. All this leads me to believe that this sound is coming from the strings vibrating against the next frets (below the fretted ones). It seems the buzz is most prevalent on the G and D strings, less so on C and not at all on A. I was wondering if possibly this mandocello might need more neck relief?

    2) Measurements: This mandocello already has a relatively high string action with the 12th fret measurements of 0.110” on C and 0.080” on A. I estimate this by the usual method of measuring the distance from the bottom of the string to the top of the fret crown.

    I also looked at string clearance under the nut i.e., the distance from the bottom of the string to the fret board at the nut: I measured 0.060” on C; and 0.047” on A side. (BTW this a fretboard has a 9" radius and a 25" scale)

    So I then took a look at the neck relief. I measured this by putting a capo on the 1st fret and pressing the string down on 14th (at neck join) -- and working a feeler gauge between the string and the 7th fret to assess the relief. I found 0.008” on C and 0.006” on A.

    That seems pretty tight and I'm not sure if that would be considered enough relief or not for strings as heavy as a mandocello?

    I wonder if I should try to dial in more relief with the truss? I put a new Stew-Mac two-way hot rod in when I made the conversion so I should be able to make some adjustments relatively easily.

    I suggest neck relief is the solution as the string action is already high?

    Thoughts?
    Bernie
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    Registered User Tom Wright's Avatar
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    Default Re: Mandocello buzz: neck relief and string action

    I would think the opposite. What is the clearance beyond the 5th fret note at fret 6?

    Relief is employed to make action easier in upper frets, but I don't like it. To me it makes the tone a little thin; I prefer the opposite, since it is easy to fret in high positions against the lower pressure. I find the low frets the challenge, so I like a convex bow, so I can keep action very low in the first frets, but still get good clearance from the rest of the fingerboard for full tone. In practice, I set my truss rod necks for almost dead straight, but biased toward convex.

    With convex bow the clearance increases away from the fretted note. Upper sketch would be normal "relief", lower is convex bow.

    Click image for larger version. 

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    Last edited by Tom Wright; Apr-27-2012 at 11:37pm.
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    Default Re: Mandocello buzz: neck relief and string action

    Thanks for the comment and ideas.

    Actually you've introduced an additional complication to the issue that I had not directly thought about. But my thinking was I need to make correction in the lower numbered frets (toward the nut).

    I should have mentioned that the buzzing is most pronounced on the lower numbered frets and not as bad at higher numbered frets (toward bridge). I started to try to pin down exactly where the transition point from buzz to no-buzz is but forgot to write it down.

    But just to be clear you prefer lower convex (= unconventional?) bow?

    Yes I believe I was thinking of going toward the upper (concave) neck bow.

    To specifically answer your question:
    If I capo the 3rd fret I have 0.005" string clearance at the 4th on C; and 0.004" on A.
    If I capo at the 5th fret then I have again about 0.005" clearance at 6th on C; and 0.004" on A.
    If I capo at the 7th fret then I have 0.006" clearance at the 8th on C; and 0.004" on A.
    If I capo at the 10th fret its the same 0.006" on C and 0.004" on A.

    I guess I really have no idea what "normal" is for this. Are these clearances enough to prevent the vibration strings from touching the fret when struck?

    Also let me mention that I would say my fret board looks pretty straight now just sighting down it but I lay a straight edge on it tomorrow.
    Bernie
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    Default Re: Mandocello buzz: neck relief and string action

    Here is a note on set up for a guitar implying that I could induce some additional clearance on the mid-numbered frets (1st to 9th) by introducing more neck relief. See the first chart in this article. However, I assume there would be a trade-off for that?
    http://www.bryankimsey.com/setup/neck_relief_1.htm
    Bernie
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    Default Re: Mandocello buzz: neck relief and string action

    Your clearances seem low, compared to next-fret numbers from the article.

    The article concludes that less relief is mostly better, except that it may involve buzzing behind the fretted note. Only in the lowest frets is there any advantage, and it is slight.

    "Given the SAME 12th fret action, less neck relief will give equal or greater next fret clearance, equal or greater mid-way action, lower mid-neck action, and lower behind the fret action. The latter could cause some back-buzzes, which might require raising or lowering the nut height. This is the only penalty that I can see for using less neck relief. "

    Back-buzzing can't be very audible, though, except for very quiet playing, since it is not connected to the bridge and sound board. Maybe there is extra wear on the low frets, which would tend to involve poor next-fret clearance for that area.
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    Default Re: Mandocello buzz: neck relief and string action

    Thanks for the thoughts. Yes, both the relief and the "next fret actions" were low on my mandocello compared to his guitar. Those were made on an electric guitar also I realized this morning. Not sure how that would impact the assessment.

    I found something else out this morning --interesting and maybe depressing.

    If I capo the 3rd; 5th; and 7th frets and then strike the strings even with considerable force there is essentially no buzzing (maybe a tiny hint) as the sound decays. This might mean that I am the problem in not pushing down hard enough?

    I don't think that hand strength is the issue --back in my Army days my hand strength was more than a standard deviation above normal for a male. But it could be that my fingers, being large, are too fleshy?

    Not exactly sure what to do about that. I would think that I play enough (hours/day) that I should have more callous than I do? But maybe additional hardening on my finger tips is the solution here?
    Bernie
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    Registered User Tom Wright's Avatar
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    Default Re: Mandocello buzz: neck relief and string action

    Personally, I would imagine that cleanly fretting a mandocello is a challenge. The issue is accuracy, as always. You may be well located for one string of the pair but too light in pressure for its neighbor. Or you could be too far back from the fret. A capo is strong enough in pressure that we usually put it halfway between frets--keeps it out of the way. But fingers need to be nearly on top of the fret, in my experience.

    Your next-fret clearance is half of the writer's, whose action height is similar at the 12th fret. Not sure how to explain that, except maybe measurement technique is different. The writer used his Tele because the adjustments were easy to change. The main point was how numbers changed in response to different relief. Nice analysis in that article, and thanks for linking to it.
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    Default Re: Mandocello buzz: neck relief and string action

    I have only occasionally played around with a 12-string guitar -- years ago. But I do not recall issues like I am experiencing here with the mandocello. Of course the heavier gauge strings on that instrument are octave no unison.

    Yes you mentioned applying pressure near the fret. I agree but on a chord like 0553 you have to get two fingers next to each other on same fret on the G & D courses -- and that is an issue for my fingers. I'll need to work on it...

    Thanks for the information. From all this I am starting to conclude that the buzzing is probably coming from one of the strings in the course actually vibrating on the fret I am using -- i.e., not the next fret down!
    Bernie
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    Default Re: Mandocello buzz: neck relief and string action

    Quote Originally Posted by Bernie Daniel View Post
    If I capo the 3rd; 5th; and 7th frets and then strike the strings even with considerable force there is essentially no buzzing (maybe a tiny hint) as the sound decays. This might mean that I am the problem in not pushing down hard enough?
    Sadly, yes it probably does.... but.... your action at the nut sounds high to me, possibly even action at the bridge, and yes if they're too high you can get into a region where it's effectively impossible to fret cleanly anyway

    Try this: push each string down just forward of the second fret - the string will now make a straight line from second fret to the nut - there should be just the very slightest gap between string and fret at the first fret. Just barely enough so when you tap on the string there you can feel it move. If you can see the gap it's too much

    With regards to neck relief - there's a lot of person preference here, but I'd like a bit more than 8thou on a guitar sized instrument - probably no more than 15thou though, so small adjustments are definitely in order.

    The what sort of bridge do you have? If it's adjustable, take it down as far as you can so the strings still play cleanly at each fret - either use a capo to check - or use your forefinger and place it real carefully right behind the fret on each string. Don't mash it down too hard though - military strength should not be required - just good placement!

    HTH, John.

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    Default Re: Mandocello buzz: neck relief and string action

    Quote Originally Posted by Tavy View Post
    Sadly, yes it probably does.... but.... your action at the nut sounds high to me, possibly even action at the bridge, and yes if they're too high you can get into a region where it's effectively impossible to fret cleanly anyway

    Try this: push each string down just forward of the second fret - the string will now make a straight line from second fret to the nut - there should be just the very slightest gap between string and fret at the first fret. Just barely enough so when you tap on the string there you can feel it move. If you can see the gap it's too much

    With regards to neck relief - there's a lot of person preference here, but I'd like a bit more than 8thou on a guitar sized instrument - probably no more than 15thou though, so small adjustments are definitely in order.

    The what sort of bridge do you have? If it's adjustable, take it down as far as you can so the strings still play cleanly at each fret - either use a capo to check - or use your forefinger and place it real carefully right behind the fret on each string. Don't mash it down too hard though - military strength should not be required - just good placement!

    HTH, John.
    Hey John thanks for your ideas! That test you mention for evaluating the nut height is a new one to me and it sounds like a good one as well. My thinnest feel gauge is 0.004" which is about half that of a piece of ordinary printer paper.

    As you can see from all the measurements I've been round and round on this. But I am starting to think like you just mentioned come back down on the action and then start to crank in a bit more relief. Heretofore I'd been going the other direction on action at least.

    But now that I think that I have pretty much isolated the buzz as coming from one member of the course on the fret actually being used (pressed) - -i.e., not from the next fret down (bridge side) it seems the obvious solution is to make the fretting require less force -- make it easier to get proper contact of both strings on the fret? So one obvious approach to that is to lower the action?

    Right now I have ~0.110" on the C and ~0.08" on A. Maybe drop down to 0.10" and 0.070" respectively?

    Also I am going to remeasure the relief using a straight edge and feeler gauges rather than using the string -- I think I can get a more accurate assessment that way? My instinctive feeling, and that's all it is, was the same as yours 0.008" seem like very slight relief for such a large instrument.

    This mandocello is relatively new -- having been converted from an arch top guitar by adding a mandocello fret board so it is not surprising that it would not be perfectly set up right out of the box. I thought I would take a look at how much relief is on a typical guitar as a guideline. Another problem with mandocellos -- we don't have a big data base to fall back on!

    I agree it should not be this difficult fret a mandocello so something must be out of whack on the set up?

    Thanks for the thoughts. I notice other mandocello players have not chimed in meaning perhaps that they are not having this problem.
    Last edited by Bernie Daniel; Apr-29-2012 at 12:29pm.
    Bernie
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  11. #11
    Registered User Tavy's Avatar
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    Default Re: Mandocello buzz: neck relief and string action

    Bernie, I don't have a 'cello for reference, but as it's basically a guitar, the normal "target action" recommended at fret 12 is ~80thou. I don't have (or use) numbers for relief, just dial in enough to get clean notes, normally just enough so I can see there's a gap: whatever that may be (10thou?). If anything those big high tension strings should swing less than say a lightweight guitar set, so a guitar-like setup should be in the ballpark. Hopefully

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