Compound Radius Necks and Saddle Adjustment Question

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by TheGuildedAge, Jul 20, 2017.

  1. TheGuildedAge

    TheGuildedAge Supporting Member

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    Long story short, I have finally concluded after 20+ years playing I prefer a flatter fretboard. 12 inch seems to be my ideal. I am looking to dump two guitars and replace them with something I like better, neck wise.

    I am looking at a few guitars I cannot try first that have compound radius necks. How does that work when setting up a bridge?

    I know you are supposed to follow the radius of the guitar, but how does one do that on a compound neck?

    If you had, say, a 10-14" compound neck, wouldn't the saddles have to be set for the 10, so they would need to be a little higher than if the neck were just straight 14?
     
  2. David Collins

    David Collins Member

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    Same way you'd set up any guitar - by measuring and incrementally adjusting the action of each string individually.

    The only time a radius gauge is of any use in setup is for shaping one piece saddles (acoustic/archtop) which are not individually adjustable, wherein the convention is to set the saddle as far above the 12th fret as the nut is below it (though I don't always follow this rule precisely). If your nut were at 10", and 12th at 14", then your saddle would end up around 18".

    On an electric with individual saddle height adjustments though, there is no need to measure or think about radius numbers at all. Measure and adjust each string individually, and it will end up exactly where it needs to be.
     
    walterw likes this.
  3. TheGuildedAge

    TheGuildedAge Supporting Member

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    I'm glad to hear this. I just had a tech set up a guitar for me. It's a 10 inch radius. But I found myself lowering the middle strings to simulate the feel of a 12, but was afraid it was "wrong" to go by feel. My six saddle bridges don't really follow the radius, they are set up by feel.
     
  4. David Collins

    David Collins Member

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    I'm not necessarily advocating setting up by feel, but rather pointing out that with good practices of measuring individual string heights in saddle adjustments, that measuring radius is irrelevant.

    If your board were perfectly at 12" radius throughout, and you adjusted your saddles to .060" at the 12th high e, evenly and incrementally increasing this to .090" at the low e, then your saddles would end up at a perfect 12" radius, without ever having to measure or think about the radius directly.

    Furthermore, if there were any minor deviations in the board radius (as there almost always is), or you had a compound radius, then this method automatically factors those variations in and results in a radius at the saddle ideally matched to the board. I find the radius gauge method often brings a false confidence in this match by separating the actual adjustment from the true board by several degrees of approximation through specs or somewhat detached measurements.

    What you describe though, leads to uneven action above the board across the strings. Either your middle strings will be lower than ideal and more prone to buzz, or your outer strings higher above the frets than necessary.

    Wanting a flatter radius toward the bridge is an entirely legitimate goal based on personal preferences of feel, but setting up a steep radius neck with a flatter radius at the saddles is a compromise which I would call less than ideal.

    I think you're taking the right path though, in that to reconcile these goals the best course is to find a neck with a radius better matched to how you prefer your setup feel. When you have this, you should be able to setup your guitars with the feel you prefer in string radius, without the compromises you currently face of uneven action above the frets.
     
  5. TheGuildedAge

    TheGuildedAge Supporting Member

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    This is very helpful. If I am reading correctly, I feel better about my assertion that I am probably better off with 12 inch radius necks rather than tweaking my other guitars to be something they really never can be.
     
  6. trap

    trap Supporting Member

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    Suhr sets the string height at the last fret. 1/16" on all strings. Top of last fret to bottom of string. Tyler uses the 17th fret. I set my Tyler up with the suhr specs.
     
  7. swiveltung

    swiveltung Member

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    I find radius very relevent for my preferences. If you dont measure agains SOME radius, then you may have a string or two that sits low or high relative to the arc of the group. For me that ends up in clumsy picking when I pick up that guitar vs another. For a compound xx-14 I will set at 14 or 16 radius near the bridge.
     
  8. David Collins

    David Collins Member

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    My point is though, if you follow the method of individual string measurements, you can achieve a radius perfectly consistent with the board. In fact, if you have a good eye for tight measurements, this method can often match a radius better than with radius gauges.

    I simply find the use of radius gauges to be unnecessary and even impeding in setup work. When measuring above the frets, the only radius gauge you need is the frets themselves, which are naturally inherently true, and not rounded to the nearest radius gauge you may have.
     
  9. David Collins

    David Collins Member

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    All this said, for many setups (largely dependent on playing style), I do not actually aim to match the board radius perfectly, but rather find better results with progressive increase in string height from treble to bass rather than even increments of increase.

    It's a subtle adjustment, and still creates a smooth arc across, but I actually prefer the lower strings to extend slightly above the exact radius of the board.
     
    Laurent Brondel likes this.
  10. swiveltung

    swiveltung Member

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    Yes, that's what I do too. ie: the "radius" I use is cocked up a bit on the bass side.
     

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