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Why are all the strings slightly different lengths?

Discussion in 'Luthier's Corner' started by hanx, Apr 13, 2009.


  1. I'm musically naive to the extreem, but i have decided it's something i want to explore a little, starting by learning bass. But I have one question really bugging me which none of my more musically inclined friends can answer for me.

    Why are all the strings different lengths? On most bridges the strings seem to be a few millimeters to about an inch different to each other in length. But from what i think i understand if they are all played on the same frets, they should need to all be the same total length or it wouldn't be in tune? how does this work?
     
  2. Pilgrim

    Pilgrim Supporting Member

    Because different basses have different distances from bridge to tuner. Take a look at a Gibson bass headstock and at a Fender headstock and you'll see that they are so different that strings have to be long enough to account for variability.

    There are also strings for 30", 32" and 34" scale basses, plus some for longer scale basses.
     
  3. vbasscustom

    vbasscustom

    Sep 8, 2008
    i beleive what he is refering to is intonation, the saddles all have to be dat different positions to make each note sound exactly right, too close theyre flat, or sharp i cant really remember, and too far away theyre flat, or sharp. just look up intonation it should explain it better.
     
  4. I don't think this is what the OP is asking at all. I think he wants to know why the length of string between the nut and the bridge is different across strings.

    I don't have a great explanation for it other than each string needs to be at its own length to be in tune at each fret. The length varies a little from string to string.

    Even when I change strings to the same brand/model, I have to slightly adjust the saddles to get the intonation dialed in.
     
  5. Dogbertday

    Dogbertday Commercial User

    Jul 10, 2007
    SE Wisconsin
    Blaine Music LLC
    It's because the different string gauges react differently to being the same height.... when you push an E string down 10mm it will change pitch more dramatically than a G string would... need proof? just tune your E string up a whole step to F# (count how many times you turn the tuner) the tune the G string from G to A (count again) I promise they will be different... The intonation at the saddle adjusts for this
     
  6. Kevinmoore73, yeah i think that's what i mean.

    Dogbertday, i can kind of see why the saddles would be different heights, but they also seem to be different in the dimension which is parrallel to the neck, i.e. different distances from the raised bit at the head (nut?).

    which would mean that at the first fret of the second octave some would be "cut" right in half, but some would be 52% or 48% of their open length? that doesn't seem right?
     
  7. It's right if the saddles are adjusted such that the notes at that second octave are in tune.
     
  8. Here's a test for the original poster, adjust your bridge saddles so that they are all in line with each other, then plug into a tuner, and tune your open notes up to pitch. Then, check the tuning of the 12th fret of each string (which should be exactly the same note). Not only will they be a little off, but each string will be off by a different amount. I won't get into the physics of it, but this is just a visual example.
     
  9. i'll buy that it works, i just kind of want to know why?

    i'm very interented in the physics, i got bored at work one day and worked out that for frequecy and for string length the ration between neighbouring notes is the twelth root of two, now i want to know why it isn't exactly the twelth root of two.
     
  10. I don't know why it works, just that it does. I'm sure if you Googled "intonation" you'd find all kinds of information.
     
  11. Gone

    Gone

    Mar 21, 2006
    Cape Town
    Jayda custom basses, builder
    Here's my understanding.

    Precursor: The pitch of the sound produced by a string is a simple equation based on the mass per unit length (gauge), the length of the string and the tension of the string.

    Examples:
    - fretting the string is changing it's length
    - tuning the string with the tuners is changing it's tension
    - to have reasonable tension across the strings we have strings of different gauge.

    The action of the B, E, A is slightly higher than the action of the C, G, D. This means that when you press the string down unto the fret you are adding more tension to the string for the low notes than the higher, which will make them sound sharper. Dogbertday also mentioned that the lower strings behave differently to the higher strings (due to the gauge difference). To compensate for the higher tension on the lower strings (and therefore higher pitch) one needs to increase the length of the strings.
     
  12. Yeah, i can see why the strings need to be different lengths, but the combinations of the total lengths all being different but the fret spacing all being the same confuses me a bit.

    Different string heights would effect how much fretting them changed the length, but not by enough to explain the differences in string lengths i see.

    All i can think is it's not quite possible to get every note on every string exactly right? so the fret positions are kind of the compromise positions for the range of string lengths? and the notes acheived are the best aproximation feasable?
     
  13. Hi.

    Yep, intonation is the thing You're wondering about and the answers given covers it pretty well.

    You're correct about not being in tune, no (stringed/reed) instrument can be absolutely in tune. A pure sine wave oscillator synth can be "absolutely" in tune (within the crystal frequency), but the complex chords sound really sterile and weird (and NOT in tune).

    There was a good thread about it a while back, and I think I even posted on that thread, but I can't find it :(. Hopefully someone can, and posts a link.

    The thread had some links to the physics side of different tuning methods: why some notes need to be a bit flat or sharp to get a pleasing result, why some tunings are preferred to some styles of music, etc.

    Regards
    Sam
     
  14. yeah that would be cool T-bird if you can dig it up.

    This was where i tangented to on my attempt to paractice today, i was really tired so not up for anything new like actually playing it, but maths and measuring suits me fine. The first few frets agree quite well but the last few (given the difference in length between strings is a greater proportion of the fretted length on lower frets) are further out.

    graph.

    i think someone was saying in the debate about 21 frets VS 24 frets that the bottom frets didn't sound so good anyway, and it was better to use the next string over higher up the fret board. Could this be the reason?
     
  15. Son of Magni

    Son of Magni

    May 10, 2005
    NH
    Builder: ThorBass
    Many people believe the need for the intonation adjustment is that fretting the string increases the tension. While it undoubtedly does change the tension, this is not the primary reason for the intonation adjustment on fretted stringed instruments.

    The cause is a characteristic of the strings called inharmonicity. This is the same characteristic that is compensated for on a piano by a tuning procedure called octave stretching.

    There are two properties of the string that effect the pitch; tension and stiffness. And as the ratio of length to thickness becomes smaller, the effect of the stiffness becomes greater.

    Take a piece of an old E string say 6 inches long and hold one end tight and pluck the other end. It will wobble back and forth at a low frequency. Now cut it in half and try it. It will vibrate much faster. This is because of it's stiffness.

    The same thing happens when you fret a note. You're making the string shorter so the stiffness has more effect and the note gets a little sharper than the tension alone would dictate.

    So we have an adjustment called the intonation adjustment which allows us to compensate by lengthening the unstopped part of the string, and generally the thicker the string is the stiffer it is, so the thicker strings get more of an adjustment.

    :bassist:

    For more reading on this subject look at the wikipedia articles on "Inharmonicity" and "Stretched tuning".
     
  16. yeah, i guess my garph doesn't quite hold up since i only allowed for length changed by fretting in my back-of-the-onvelope deduced formula for "ideal" fret spacing.

    I guess in some sort of "perfect" instrument (the sort of "perfect" simplified system reminicent of those high-school physics exams where nothing has friction) you would only change the string length by fretting. BUT in the muddy complex real world you change all sorts of other things, such as tension etc.

    Does the difference in total string length compensate for the variable oyther than length which are alterred by fretting?
     

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