Dead spots on bolt-on guitars, G-String, 14th fret. Reason?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by RockStarNick, Feb 25, 2009.

  1. RockStarNick

    RockStarNick Supporting Member

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    I'm trying to do some research on dead spots on guitars.

    I've searched here, and found that lots of people complain about a dead spot on their strats/teles around the 12-13-14th fret on the G string.

    This sounds like more than just a coincendence. Is there a reason why a dead spot can occur here quite frequently?

    The way the wood vibrates on top of the big bots underneath? Poorly seated frets? Poorly slotted nut causing sympathetic vibes?

    Or is it just bum wood?

    Or IS it just a coincedence?
     
  2. RvChevron

    RvChevron Member

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    http://www.acoustics.org/press/137th/fleischer.html

    From a few high end builder's view, the neck needs to be more rigid. Some of them put carbon grahite rods in their neck and claim this let the neck wood resonante more freely and eliminate dead spot.
     
  3. Tone_Terrific

    Tone_Terrific Supporting Member

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    ^^I have posted references to this article before and pointed out the loss peak that occurs at the g string 14-ish fret, 450-ish hz. Note that the diagram is showing loss peaks.
    I think various factors, including the one that I like to play in that position, makes it more conspicuous.
     
  4. RockStarNick

    RockStarNick Supporting Member

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    Yeah, TT, your threads are the ones that I found.

    Very interesting article above there.
     
  5. uOpt

    uOpt Member

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    A fret level is a good first step.

    Something in the guitar might have a resonance frequency there and suck this tone. The trussrod would be an example.

    Does the problem go away if you tune the string 2 halftones down? If yes, it's something resonating. If not it's probably frets.
     
  6. bluesjunior

    bluesjunior Member

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    I have one dead spot on my strat the "A" at the 7th fret on the D string. I first noticed it after I re-set up my guitar from Eb tuning to Standard tuning about a year or so ago. I mentioned it in a previous thread here on the subject and the consensus seemed to be that some guitars are just that way and as it was the only note on the entire fretboard with any sort of problem I just decided to live with it. Until last month when while changing strings I decided that I preferred the sound of my strat in Eb tuning, re-set the action and checked the intonation. I tried the dead spot and whoopee there it was that 7th fret note G# on the D string was sustaining all day long but my joy was short lived as all that had happened was that it had moved up one fret and now the A at the 8th fret was the dead spot. I guess I am just going to live with it but man guitars are weird.:huh
     
  7. uOpt

    uOpt Member

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    No, you have something loose in that guitar that has exactly this resonance frequency.

    I'd take everything apart and look for loose stuff.

    Shake the neck to see whether the truss rod rattles.

    Vintage tuners and their bushings can be responsible.

    Obviously everything bridge related.

    The pickup mount.
     
  8. Lex Luthier

    Lex Luthier Member

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    Sometimes it is just the design of the guitar that makes it prone for dead spots, take for instance early production PRS guitars which are notorious for dead spots for some reason.
     
  9. Rosewood

    Rosewood Member

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    Yep, first guitar I built had a dead spot on the B string and nothing would stop it, except maybe installing carbon fiber rods under the fingerboard.
     
  10. bluesjunior

    bluesjunior Member

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    I went over that guitar with a toothcomb today and there is absolutely nothing loose on it.
     
  11. Terry McInturff

    Terry McInturff 40th Anniversary of guitar building! Gold Supporting Member

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    Clamp a c-clamp to the headstock and watch that problem dissapear.
    It's neck resonance issues. I could practically write a book about it.

    No cure for a neck that suffers from that (unless the fathead thing works) and no..internal carbon fiber rods have very little effect.
     
  12. Lance

    Lance Member

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    Do you think one of those clamp on capos would have enough tension to take care of this?
     
  13. uOpt

    uOpt Member

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    There's some sustainer product, I think by Ernie ball, which is a weight with a rubber-protected clamp that you can buy for $20.
     
  14. fumbler

    fumbler Member

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    ++1 on resonance issues.

    The OP said "bolt-on" necks. All strat necks have the same length and therefore will have similar resonant frequencies (the thickness doesn't matter much for the resonance). That's why dead spots often occur at the same spot.

    You can change where it is by changing the mass of the headstock (with a clamp or with heavier/lighter tuners; or a cast-iron logo:NUTS) but you can't remove it.

    I think extra-stiff necks (with graphite rods or even an all-graphite neck) still have a resonant peak but the frequency is high enough that it's no longer a problem for the range of a guitar.
     
  15. RockStarNick

    RockStarNick Supporting Member

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    I've recently built 2 of my own guitars, using parts, and slightly noticed it on one of them.

    I never noticed it on my 1996 Am Strat, but that's because that thing has a freakishly rock hard neck. Never had to adjust it ONCE in about 14 years. Through hot and cold and everything.

    Just built anther new one, and don't REALLY notice it, but its gotta set in to realy see.
     
  16. Keyser Soze

    Keyser Soze Member

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    It's not the tension of the clamp that is changing the behavior of the neck. It is the added mass altering the vibrational characteristics of the neck. Sure the clamp may eliminate the offending dead spot, but it may also create one somewhere else on the board.

    There are similar devices placed on the muzzle end of precision rifles intended to tune their behavior. These are a bit more reliable since rifle barrels, being made of relatively uniform material in well defined shape, are much more predictable (and repeatable) in their behavior.

    Guitar necks, being a rather complex mix of wood(s) and metals in odd assymetric shapes, are going to prove alot harder to 'tune' using added mass. Not impossible, just damn unpredictable.
     
  17. mpr

    mpr Member

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    Sadly, I also have some of those. Not on a Fender, nor Fender shape, but it is bolt-on and 25.5" scale length. And there it is, G string, around 12th fret. There may be more, I'll have to map it out in detail.
     
  18. Rod

    Rod Tone is Paramount Supporting Member

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    Terry, Is it because of the resonance of the wood used for a particular neck coupled with a different resonance of a metal truss rod?
     
  19. Wesley Owens

    Wesley Owens Member

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    Just thinking out loud here, but I wonder if a lack of harmony between the resonance of the neck and the body in a bolt-on would be a large contributing factor to this problem. It seems a bolt on guitar would resonate best overall if the neck and body were tuned to work together, much like tuning the top and bottom plates of an acoustic instrument. And in turn, that resonance being in tune relative to how the guitar is tuned, ussually relative to A-440. To those having this problem, tap the neck and body of the guitar and see if they work together or if they are fighting each other. Keep in mind that they don't necessarily need to tap to the same note to be in tune. They could tap to two notes in relative harmony with each other and be considered "in tune". If they are in tune with each other, then I wonder if the overall resonance of the guitar being out of tune as related to A-440 plays into the problem. I don't have any personal experience with this issue, but I am curious if that might be a factor.
     
  20. John Coloccia

    John Coloccia Cold Supporting Member

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    Ja ja. One demo I've started dong for people is I place a tuning fork on the bridge, and then I place it on the neck near the nut....and the acoustic coupling is VERY similar on many guitars. The neck in that area can be very active on some guitars. Sound engineers know this. Savvy sound engineers setup a mic on the neck to get a really natural sounding acoustic guitar.
     

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