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Thread: close to topic- fret spacing

  1. #1
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    Default close to topic- fret spacing

    At long last I've gotten back to one old project, the alumitar- aluminum electic guitar. I found the figures I had calculated for fret spacing and wanted to check them for accuracy. Then I started reading about stretch compensation which counteracts the increase in tension of a string when you bend it to touch a fret. I was surprised at the relatively large difference in fret spacing when the compensation factor was put into the equation. For example, at the tenth fret, there's about a .070 difference in the position where the fret should be. That sure seems like a lot when you consider that the fret positions are calculated to four decimal places- not that I know of anyone who can saw a fret slot that closely. My questions, how close is good enough, say for a trained ear, and are there any frets which should be very finely positioned because an error there would be most noticable? I can imagine that at a harmonic, that fret position would be more critical.

    I've decided to go with the compensated figures since from one simple test using a keyboard and beat tones, the positions given seem to be right on the money. What I have read about equal temperment, etc, suggests that many of the notes could be altered slightly in their frequency (by positioning the frets differently than the standard formula suggests) to achieve a more pleasing sound. After all, hearing a guitar being played is supposed to be pleasant- not getting into the relative merits of differing types of music-.

    I'm aware of pretty much all the parameters regarding intonation and adjustments, including the effects of different brands of strings, the height of the strings, the curve of the fretboard under the strings, etc, but the rather broad range of possible fret positions seems like an anomaly to me. If a guitar is properly in tune, what kinds of changes in fret position might make it sound even better that it normally might? Does anybody ever add a compensation factor for average finger pressure?- that alone seems to me to be a much larger factor than small deviations in fret position.

    Comments, anyone?

  2. #2
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    My questions, how close is good enough, say for a trained ear, and are there any frets which should be very finely positioned because an error there would be most noticable? I can imagine that at a harmonic, that fret position would be more critical.
    I haven't tested my frequency resolution in a long time but I do have perfect relative pitch. What that means is that if you give me a note I can then give back any other note accurately relative to the tone supplied. When I tested that back in high school I was good to about 1/4 cycle per second at 440 hz (American Standard A). Since the next semitone, B flat, is the 12th root of two higher at 466.16372 hz that corresponds to a sensitivity of about 1 percent.

    I don't know how my tone discrimination compares with others but it doesn't take much off key for me to notice. This is particularly apparent in the beat frequencies. In fact, I don't really like the equally tempered scale as it is not a perfect tuning.
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  3. #3
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    darryl, you might consider sending a private message to Frank Ford on this as I believe it would be right up his alley. Incidently, I'm may need to pick your brain as I'm pondering a lap steel project for the winter and since I'm a total newbie, I'm going to need some serious guidance.
    John B

  4. #4
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    Never heard of it done at the frets. At the bridge, yes.

    The tuning of a guitar and even a piano are a comprimise. The human ear actually likes a tiny bit of what seems to be out of tune.

    Is this going to be an "all" aluminum guitar? Seems like it would feel cold. And prone to bad vibrations.
    Last edited by topct; 08-26-2007 at 07:39 AM.
    Gene

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    The human ear actually likes a tiny bit of what seems to be out of tune.
    Speak for yourself. I like perfect tuning. It does mean playing in only one key though unless you retune, a somewhat awkward proposition for a piano.
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  6. #6
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    Actually, there are a lot of aluminum guitars around. I suppose they are used to play light metal music...
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  7. #7
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    Quote Originally Posted by topct
    The tuning of a guitar and even a piano are a comprimise. The human ear actually likes a tiny bit of what seems to be out of tune.
    In the visual art world it's called "evidence of hand". If it exist there, no reason it shouldn't exist in music. It's one of the reasons I maintain we live in a analog universe and not digital.

    As for the OPers question, I'm betting it ain't that critical. If it is, explain to me how they made guitars hundreds of years ago.
    Last edited by Your Old Dog; 08-26-2007 at 08:33 AM.

  8. #8

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    Quote Originally Posted by topct
    The tuning of a guitar and even a piano are a comprimise. The human ear actually likes a tiny bit of what seems to be out of tune.
    Temper is actually a little more complex than that. It stems from the oddity that if you set perfect intervals going up the scale, then perfect intervals coming down, you wind up with a slightly different note from where you started. Tempering is an attempt to deal with this remainder. If the error is distributed among all the intervening notes it's equal tempering. However, this seems to just make any key sound bad. The more common strategy is even tempering which distributes the error unevenly, assigning more of the error to keys that are used less frequently. That's why transposing a piece of music to a different key can make it sound different. If all things were equal, transposing a piece would make it just the same except at a higher or lower pitch. Because of the uneven distribution in even tempering the color of a piece can change in a different key. In modern times we've become accustomed enough to even temper that we hardly notice, but in the Baroque era they were much more sensitive and struggled with how to solve the problem. There some instruments made with multiple keys for the "same" note tuned for diffent keys so you could actually play the correct note in that key. Didn't turn out to be a very viable solution.
    .
    "Opportunity is missed by most people because it is dressed in overalls and looks like work." Thomas Edison

  9. #9
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    Darryl, did you happen to see this?

    http://www.charliehunter.com/gear/novax.html
    Gene

  10. #10
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    Yep, I've played with people that say they have perfect pitch and they are constantly tuning the instrument because it never sounds right to them. When they get it right in one tune and we play another tune they start tuning again to get the strings right. We no longer stop playing for them to tune.

    Having perfect pitch is a curse if you want to enjoy the music. They even complain that the music is out of tune on a recording, which I am sure it is to their ears.

    I just tune it and play it and enjoy it. I'm glad I'm not afflicted with perfect pitch.

    Most guitar finger boards have the fret slots cut with a CNC machine. They can program the spacing for the length of the strings from the nut to the bridge and have it sound ok but it will never be perfect and always sound off to those with perfect pitch.

    I would suggest you buy a ready made finger board rather than cutting your own.
    Last edited by Carld; 08-26-2007 at 05:34 PM.
    It's only ink and paper

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