Open G is flat compared to harmonic (DB forum thread)

Discussion in 'Strings [DB]' started by Michael Case, Dec 11, 2012.


  1. Michael Case

    Michael Case

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    So, when I tune my G to the D string harmonic, the open note is flat. Is this a string issue? Or a set up issue. I use Spirocore Weichs that I've had on my bass for about six months. They weren't new when I got them, but they look lightly used.

    Thanks
     
  2. LB75

    LB75

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    Sounds like an intonation problem.
     
  3. Got2SadowskyNYC

    Got2SadowskyNYC

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    Yep. intonation is slightly off.

    If it's lower you need to shift the saddle towards the nut slightly, retune all the strings and recheck.

    Higher, move the other direction.
     
  4. two fingers

    two fingers Loud Mouth Know It All Blowhard

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    Yep. Intonation. Just look up a couple of youtube videos on setting intonation so you can wrap your head around what the guy above me said. He's right.
     
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  6. Got2SadowskyNYC

    Got2SadowskyNYC

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    Tip: You need an accurate tuner, like a Peterson, Korg Pitch Black, Planetwaves trustrobe. Something with a 0.1 cent rating.

    A Boss tu2 or 3 or other common tuner is not accurate enough. The more accurate the tuner the better the tuning.

    Some tuners, like Peterson, have "sweetened" setting for specific insruments. Do NOT use these. Use the normal setting.
     
  7. donn

    donn

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    Just for the benefit of clueless onlookers like me who are following along from home, could someone explain this?

    What I suppose he's talking about is, getting the G string 3rd partial (D) to match the D string 4th partial (D.) If the G string 1st partial is not then reasonably close to G, then ... evidently the string is not in tune with its own harmonics? which would mean time for new strings.
     
  8. Got2SadowskyNYC

    Got2SadowskyNYC

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    Although old string can cause tuning issues, the fact that the problem is on 1 string and not the others leads me to believe it's an intonation problem.

    Part of setting up is tuning the harmonic at the 12 fret with a tuner and then freting it. They should both be in tune. If it's off on one string that string will not play in tune with the others even if it's open in tune. This "out of tuneness" gets progressively worse as you play up the neck.

    Let say you play a chord using an open string and fretted strings above the 12th fret. The chord won't be in tune with itself. This is what "pleking" and the Buzz Fieten nut correct.
     
  9. Andrew McGregor

    Andrew McGregor

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    This being a double bass forum question... yes, it is related to intonation of the instrument. However, you can't do anything about it on a DB, this just happens. It's perfectly normal, and you need to know about it and choose your adjustment... either just tune a bit sharper or know it's flat and adjust. But be consistent about what you do, or your intonation will suffer.

    As for physically how this is possible, the bridge (or saddle on a BG) vibrates, so the effective node at the end of the string is somewhere a bit past it. How far depends on several things, but the end result is the harmonics are a bit sharp.
     
  10. Got2SadowskyNYC

    Got2SadowskyNYC

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    OH CRAP. I didn't realize this was double bass question. It's obvious by what I was saying. I was using the "new post" button.

    Sorry fellas. I'll pay more attention next time.
     
  11. donn

    donn

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    Thanks - would have never guessed, and in the event I ever noticed it myself, I would have been mighty confounded!
     
  12. iiipopes

    iiipopes Supporting Member

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    Actually - try this instead - it should be slightly flat.

    Open D, if tuned to equal temperament in relation to A=440, is @ 73.42 Hz, and the 4th harmonic D will be @293.66 Hz.

    Open G, if tuned to equal temperament in relation to A=440, is @ 98 Hz, and the 3rd harmonic D will be @294 Hz. "Natural" perfect 5ths are slightly sharp compared to the equally tempered 7th semitone.

    SO...if a player tunes his 3rd harmonic upper string to the 4th harmonic lower string, it is effectively lowering that 3rd harmonic, so the fundamental on the upper string will be flat, and the string has to be tweaked up slightly, just like an organ or piano tuner has to lay the bearings and set the temperament accordingly also.

    Yes, tuning this way, the 3rd harmonic G string to the 4th harmonic D string, the open G will be slightly flat. The OP has great ears.
     
  13. eerbrev

    eerbrev

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    this is why I use a tuner for my strings, and not the harmonics. when I do use harmonics, though, I use them in this manner:

    Open G - octave Harmonic on the D
    Open D - octave Harmonic on the A
    Open A - Octave harmonic on the E

    using the 5ths instead of the 4ths or octaves I find I can get the strings in tune with each other in a manner more pleasing to my ear. It's an interesting experiment

    eerbrev
     
  14. donn

    donn

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    ... if he's bugged enough about the one tenth of a percent difference between these two harmonics to complain to talkbass - yes.
     
  15. iiipopes

    iiipopes Supporting Member

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    Yeah, it used to bug me also when I played electric guitar in garage bands. Several of my instruments, including my #1 custom fanned fret electric bass, even have the Delft-style nut shims to make sure intonation is secure. I always used to love the guys who would carefully tune up their E and A chords, and then complain why the C and D chords were not in tune!
     
  16. Tommy el Gato

    Tommy el Gato

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    I've actually had similar problems. Some of them I've fixed, but one in particular I haven't.

    Basically, my open A used to sound 5 or 6 cents flat compared the the A and E harmonics that you use to tune the E and D string. But the octave A harmonic (12th fret for the BGers) was closer to 11 or 12 cents flat. Actually the latter harmonic was a wolf tone and that screwed up overtone was affecting the way the rest of the instrument resonated. Putting on a wolf tone eliminator made a number of registers resonate more clearly on my bass. However, the A440 harmonic on my D string sounds about 5 cents sharp when the rest of the harmonics on this string are in tune (including the open string). I still haven't fixed it, but I'm able to compensate for it pretty easily just by tuning with a tuner and checking all of my harmonics.

    Oh, and all of this has happened consistently with a number of different string makes/models.
     
  17. DoubleMIDI

    DoubleMIDI

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    I'm afraid too many things are mixed up and influences the whole thing.

    The partials (called harmonics) of the strings are never exact overtones in a mathematical sense due tue string stiffness which make them higher (the more distant from the base frequency the more). This is also the reason for the need of stretched tuning in pianos.

    Our hearing nowadays is more trained to equal temperament than just intonation. And the direction to correct the tuning of our instruments to what we hear is sometimes wrong because of mixing things up.

    The deviation of the pure fifth from the equal temperament is about 1.5 cent (the pure fifth is higher). Even three of these intervals have a total deviation of less than 5 cent. The same for the fourth, but the deviation goes into the other direction (the pure fourth is lower).

    When strings are getting older they stretch over time. The windings might not stretch equally with the string core resulting in a non-uniform mass distribution which influences the frequencies of the partials, probably in different directions (resulting in a recognizable inharmonicity of the string).

    So it is hard to say which influences are larger than others. Use your ears using different tuning methods and maybe a tuner and your ears to control the result and correct if needed.
     
  18. iiipopes

    iiipopes Supporting Member

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    Yes, that is the next step. Because a string has mass and diameter, and is over a bridge, the string does not vibrate "purely," but can vibrate differently from edge touching the bridge to the edge farthest away from the bridge, almost like a hinge. This is especially pronounced on piano strings, and is why piano tuners "stretch" the octaves: the octave harmonic is actually a hair sharp compared to the fundamental.

    http://www.afn.org/~afn49304/youngnew.htm

    Since this makes the harmonic used for tuning even more sharp than simply the math of the tuning, it follows that this exacerbates the tuning issues of the open string, rendering the open fundamental string as being even more flat using the harmonics to tune.
     

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