Truth is that guitar string manufacturers and guitar manufactures have been lying to us, the thing is really there is no good reason for it. Most prepackaged guitar string sets are all wrong because they are not optimized for the notes and scale lengths that they are intended for.
The fact is that for every string gauge (thickness) given a fixed scale length, there is an optimal tension range where good sustain is achieved and fretted notes still sound good and feel good. Then there is a range of notes above and below that optimal tension that will work, but the note will sound increasingly floppy or lose sustain on the upper end.
For example, let’s take a look at a “standard” D’addario exl110 electric guitar set:
Notice no two strings have the same tension very few are even within a half pound, and there is no rhyme or reason as to why. Some notes will sing, While others will sound flat and muddy. This wasn’t lost on D’Addario so they have now introduced “Balanced” string sets. This is the exact same nickel steel wound string in a balanced configuration. The exl110BT set:
Notice that in this set, everything is in the 16-17 pound tension range? If you compare this set to the “standard” set only the high E and the high G where in an optimal range. ( Note: I have no idea how they magically reduced the tension of a .046 from 17.5 in standard set, to 16.9 on a balanced set, but for now let’s assume they’ve figured this out)
So what does all of this mean to people who build and play guitars, especially in open tunings? It means that prepackaged sets of strings are an exceptionally poor choice as a starting point for our homemade instruments.
To begin with, D’ Addario uses a 25. 5 inch scale to calculate all of their string tensions. This is the scale that fender uses on Stratocasters and Telecasters. However, Gibson uses a 25 inch scale on most of their instruments. While the low E (.046) on the above set yields a tension of 16.91 on a 25.5″ scale, on a 25″ scale that tension rises to 18.44 (calculated using http://www.mcdonaldstrings.com/stringxxiii.html). That’s a pretty dramatic difference. Scale length is a critical component in achieving optimized tension. (Note: this doesn’t make sense, shorter scale tension should decrease tension using the same scale, some thing smells funny with the data from the string companies and the calculators)
So let’s take a look at what a 25″ scale GDGB tuned cigar box instrument should have for strings shooting for a 16.5 pound tension.
B .014 17.01
G .017 15.86
D .022 17.16
G .036 16.32
Using commonly available strings this is really as close as we can get, but no pre packaged sets include the four gauges that I am aware of. Also notice that the “balanced” D’Addario set comes with at least one not so common gauge for the high B, .0135.
You are much better off assembling your string sets together from singles if you are using alternate tunings or non traditional numbers of strings.
For a very “colorful” explanation of string tension see: http://www.zacharyguitars.com/Strings.htm
D’Addario publishes a string tension guide that you can find here: http://daddario.com/upload/tension_chart_13934.pdf
And the string tension calculator I used, can be found here: http://www.mcdonaldstrings.com/stringxxiii.html
Thanks to Penny Nelson for this handy tension calculator as well http://wahiduddin.net/calc/calc_guitar_string.htm