Open low B intonation problems led to ridiculous compensation

Discussion in 'Pickups, Electronics & General Tech' started by Crocus, Nov 10, 2017.

  1. Crocus

    Crocus SS.org Regular

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    Greetings.

    I've got a Schecter and a set of GHS 7-String Boomers (10-60), and there are intonation problems on 7th string I fail to comprehend. The neck and frets are ok, the action is ok on both 1st and 12th frets (a tiny bit higher on 7th but nothing that could explain that), and I've made the most of Tune-o-matic. I ended with decent intonation on high E to low E. But open fret is 7 to 10 cents lower than 1st and higher frets on low B.

    So I've made some calculations and quickly prototyped a compensation nut to see if it helps. Now the intonation seems decent on low B (+-3 cents, but I don't expect it to sound or intonate good after 12th) and nice (+-1 to 2 cents) on the rest. High E to low E were compensated for 1-2mm, but for low B it's 6mm!

    nutjob.JPG

    I wonder what's going on there. I've never witnessed or even heard of a problem like that for a single string. Can this be specific to current set of strings, and if it can, then how? What's the theory behind this beautiful phenomenon? Please, enlighten me.
     
    Last edited: Nov 10, 2017
  2. diagrammatiks

    diagrammatiks SS.org Regular

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    are you already out of range at the bridge? t
     
  3. Crocus

    Crocus SS.org Regular

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    No, within the range. I've fine-tuned saddles to the point they could help (match open, 12th fret and 12th harmonic). That's where I started to compensate.
     
  4. Winspear

    Winspear Tom Winspear

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    Sounds like your nut must be cut too high.
    Fret the 2nd fret and the string should pretty much contact the 1st fretwire. Can you take a pic?
     
  5. Crocus

    Crocus SS.org Regular

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    That's reasonable conclusion, but it isn't. The action on the 1st fret is around 0.6-0.7mm for low B and 0.5-0.6mm for the others. Seems like nothing that could explain those 7 to 10 cents flat on open low B.

    nutjob.JPG


    When 2nd fret is fretted, there's a paper thin gap between 1st fretwire and a string, just as intended.

    nutjob-2.JPG

    Hope the photos are good enough to illustrate this.
     
  6. Lorcan Ward

    Lorcan Ward 7slinger Contributor

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    Some guitars just don't intonate well across the board. What model is it? My Schecter 7 was awful in a few places, mostly the bottom string so I installed an Earvana compensated nut which fixed everything.
     
  7. Crocus

    Crocus SS.org Regular

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    That's Schecter C-7 SGR. I didn't expect much from it without seeing a tech, but it performs quite ok. The intonation of other strings is fine, that's why this confuses me. Earvana was the first thing I looked at, but the calculations convinced me that such a small thing cannot compensate low B problem.
    I'm about to go heavier string gauges and still hope that this is GHS Boomers' fault (although I've seen no feedback on their intonation problems). But I'd like to get an idea on what's going on before destroying the nut.
     
  8. tedtan

    tedtan SS.org Regular

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    Different string brands can intonate differently, so you can experiment with various brands. You may have to try different gauges for the low B, too - anything from .056 to .066 to find what intonates best.
     
  9. larsmul

    larsmul SS.org Regular

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    It is weird that you had to shorten the scale on low strings , usually it is the contrary .
     
  10. laxu

    laxu SS.org Regular

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    You can sometimes have crap strings that do not intonate correctly. Stopped using DR strings because I kept running into that issue. If the strings contact the nut slot first at the fretboard side edge so the nut is fine, then maybe the bridge is installed slightly off?

    I would probably contact Schecter about it.
     
  11. marcwormjim

    marcwormjim SS.org Regular

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    Earlier, I emailed D’Addario about a bad D string in a NYXL set that intonated a semitone flat at the 12th fret. Just replaced it with a spare GHS nickel rocker and it’s right-on.

    Just posting that here to remind folks to always rule out the string when encountering these problems.
     
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  12. Crocus

    Crocus SS.org Regular

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    The bridge is fine as well, so the axe can be ruled out from the equation, I guess. Moreover, I quickly placed a 6th into 7th position (not vice versa to not hurt the nut), and a 6th tuned ok there. So I guess it's the problem is this 7th string, thanks for confirming this. Just not sure how this is possible and what is the physics behind this. The 7th is quite stiff (GHS proclaims heavy core as a feature), but all .060+ strings are.
     
  13. ElRay

    ElRay Mostly Harmless

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    Compensation at the bridge and nut address different things. In a nutshell, bridge compensation addresses inelasticity of the string and non-zero thickness, nut compensation address the added tension when fretting on the first few frets.
     
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  14. Crocus

    Crocus SS.org Regular

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    I have a suspicion that in my case nut compensation addresses inelascticity around nut region as well because of higher stiffness of my 7th. That's one of the explanations I came up with (another one was black magic).
     
  15. elkoki

    elkoki SS.org Regular

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    it's probably that the string gauge is too thick for the nut.? I'm not an expert at this, but when i've tried thicker gauges on my Schecter 7, the intonation obviously needs to be reset, when I went to reset it, I had to tighten all the saddles way too much and the low B just wouldn't intonate for shit. After I switched back to the gauge that it was set up with, everything went back to normal.
     

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