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Thread: Why not even tensions within a string set?

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    Registered User swampstomper's Avatar
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    I'm doing some calculations to find optimum string gauges, using the formulas in the D'Addario guide (http://www.daddariostrings.com/Resou...sion_chart.pdf)

    I discovered that there is a substantial difference in tension within their sets. For example
    -- the j74 is 23.2 / 19.2 / 23.3 / 25.1
    -- the j75 is 25.4 / 21.9 / 23.3 / 26.4
    -- the j76 (mandola) is 25.2 / 28.4 / 25.4 / 25.4

    My question: why is the A string in the two mando sets at such a low tension? It seems the 0.015 (j74) and 0.016 (j75) should be replaced with 0.016 and 0.017 (yes this one is available as a single). The tensions would then be 21.9 (J74+) and 24.7 (j75+), much closer to the other strings.

    Related: why is the D on the j75 the same as the j74? There is no 0.027w (why not?), but the 0.028w would give a tension of 26.7, almost the same as the 0.041 on the G string.

    Similarly, on the mandola, why use a 0.25w (tension 28.4) for the D when a 0.24w (which is available) would give 25.5 tension, almost exactly the same as the other strings.

    It would seem that equal tension = equal stress, and (?) equal volume between strings.

    Enlightenment, please!

  2. #2

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    The conventional thinking for modern instruments is that the highest pitched string should be of higher tension because the trebles don't project as well at distance. Increasing the tension of the treble-most string increases its brightness in the attack and helps balance projection with the bass. This seems to be in general keeping with the mandolin strings you've listed. I don't know why the convention isn't applied to D'Addario's mandola strings. I'm interested in why others think that may be.

    Some lutenists and other early-instrument specialists have been experimenting with uniform tensions throughout their instruments. I'm not certain of my opinion on that yet.

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    My theory, as a novice at the mandolin, is that the A string is meant to build callouses on the fingers faster...It feels like a steel rail next to the other strings, especially in the morning just after getting out of the shower, when my fingers are softened from the water...not sure why I like playin' my mando while I'm still half-nekkid, but I do...it's just hard on the fingers...

    Thanks for the post, by the way...I had been wondering about this for some time...thought I wasn't tuning it right, but the sound was there, so I kept going. That A string's a bugger,though.
    Give me bluegrass or give me The Grateful Dead.

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    Check out the GHS A260 set, endorsed by Bobby Osborne. They vary by about 2 lbs. across the neck. As far as I know these are the most evenly matched of any string set.

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    Registered User swampstomper's Avatar
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    Thanks for the insight.

    Eugene, your theory doesn't seem to hold here because the G (lowest) has in fact the highest tension in the mandolin sets, and the D (2nd) the highest for the mandola.

    Darthstar, your post got me thinking that the lighter A is because a thicker non-wound would really be murder on the fingers.

    The GHS A260 is .011, .016, .024w, .038w However what is really needed is the unit weight of the strings; D'Addario gives these but GHS doesn't (as far as I could find on their site). Assuming the steel and phosphor bronze wound are the same unit weights as the D'Addario (i.e. 0.00002680 0.00005671 0.00011352 0.00029110 lb/in) the tension would be:

    23.2, 21.9, 19.5, 22.3 lbs.

    So Michael you are almost right: they vary by 3.7lbs from the E to D. Interestingly, the D is now the lowest tension. But of course I don't know if these are the right unit weights.

    If you're curious, here's the formula in the R language:

    ten <- function(uw, l, f) { (uw * (2*l*f)^2) / 386.4 }

    where uw is the user weight in lbs/in, l is the string length in " (standard mandolin 13 7/8"), f is the frequency of the note in Hz (standard mandolin + low C:

    e'' a' d' g c
    659.2 440.0 293.7 196.0 130.8

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    Registered User Bob DeVellis's Avatar
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    It seems to me the ultimate criterion is how it sounds, not what the tension is at pitch. For example, an instrument might be more responsive to some frequencies than others so that a less-tensioned string at that frequency sounds more balanced. Or the overtones may differ for different strings at the same pitch. Also, I'm not confident that more tension necessarily translates to more volume, although some of the time it will. The "balance" that seems optimal might therefore be not just a balance of tensions across strings, but a balance of all the components influencing the sound. Of course, the string maker can only guess at what balance will suit any particular instrument, or more likely, package their sets so as to be optimal for the "average" or "typical" customer's mandolin.
    Bob DeVellis

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    Registered User swampstomper's Avatar
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    Bobd, I think you are completely right, the sets are compromises based on typical mandolins or mandolas. So they're saying that the a' projects better so can use less tension? The outside strings e" and g are higher tension, maybe because a typical mando doesn't project those frequencies so well?

    The reason I got into this topic is that I'm designing a mandolin/mandola (5 course mandolin) with a local luthier. We want to use a 15" scale as a compromise, but we were also looking at different lengths. So I went to calculate the tensions to find the strings we will use. For example, the e" would be too thin at standard mandola length, so we shortened the scale. Since we haven't built the instrument, we don't know how it will respond! So my thinking was to start with equal tensions and then adjust as the instrument works in.

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    Quote Originally Posted by (swampstomper @ April 08 2005, 08:41)
    Eugene, your theory doesn't seem to hold here because the G (lowest) has in fact the highest tension in the mandolin sets, and the D (2nd) the highest for the mandola.
    Why, that's even more funky than I thought!

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    Quote Originally Posted by (swampstomper @ April 08 2005, 10:07)
    The reason I got into this topic is that I'm designing a mandolin/mandola (5 course mandolin) with a local luthier. We want to use a 15" scale as a compromise, but we were also looking at different lengths...
    This has been done by a number of different builders in the past, most notably in the US by Vega. There is also a breed of 5-course mandocello named liuto cantabile or liuto moderno built to be tuned C-G-d-a-e'; it was popular in Italy in the early 20th c. Vega even dabbled in them.

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    Registered User swampstomper's Avatar
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    Yes, my luthier is basing the scale on an early Lyon & Healy 5-course mandolin. This was Washburn of course (the old one). The liuto cantabile sounds impossible to play! It would have a very long scale length to get to C (the mandola only goes to c), maybe 22" or even 24", right? Then if it's tuned in 5ths (not 4ths like the guitar) the stretches would be beyond my capabilities!

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    The Calace shop still produces liuto cantabile models. They clock a whopping 61 cm (24")...but that's not atypical for mandocello/mandoloncello. In citing inspiration for the liuto cantabile, it's often said that the e' was added to make the mandocello a viable solo instrument. Ouch!

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    Swampstomper, when calculating string weights I would think one should have precise information rather than guessing at what a string weighs. There is a difference between GHS and D'Addario in that one uses a larger core wire with a smaller wrap wire and the other goes the other way. The thicker core wire will make a stiffer string requiring a bit more compensation at the bridge.

    Have you given any thought to a 'fanned fret' fingerboard? It would help accommodate the range of strings you need for your 5 course instrument.

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    Registered User swampstomper's Avatar
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    Michael,

    I agree that exact weights are needed. I have these for the d'Addario strings; unfortunately GHS doesn't provide that info. on their web site.

    I visited your site -- very nice! if somewhat out of my budget (well, I can always dream!) The wingfeather design looked really cool -- an archtop guitar with mandolin strings, if I see right. How does it sound (good, I know, but I mean, what are its tonal qualities?).

    But I could not find out what you mean by "fanned fret". Is that different string lengths at the bridge, and then the frets are at different positions (slanted I guess)? That's an interesting idea. The e" would then be the shorter string (to allow heavier-gauge strings) and the c the longest if I understand right.

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    Check out Novax guitars for the fanned fret idea. It works well on acoustic instruments as well.

    Re. Wingfeather mandolin, it is one model of my 'Ritz' series, which are guitar shaped bodies. They can be braced and 'steered' toward a particular tone. They can be made to sound like a bluegrass instrument or to have a rich and warm voice. Just like most other body designs they can be adjusted for tone during the assembly process.

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    Registered User swampstomper's Avatar
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    Wow, the things I am learning on this forum! Many thanks for the link, that site with the historic instruments is fascinating.

    Now I have to think about how I'd adjust my fingering to the fanned frets... it's really an interesting idea and would solve the problem of a too-thin treble and too-thick bass strings.

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