One of the first considerations for a new 12-string owner is tuning the guitar. The nearby photo of Leadbelly playing his Stella 12-string reminds me that Leadbelly tuned his guitar down to C, maybe even to B. That is, instead of E-A-D-G-B-E (6th to 1st string), his guitar would be tuned C-F-Bb-Eb-G-C. That doesn’t result in quite as low of a string tension as you might expect because the scale length of his guitar was 26.5 inches, an inch longer than is common now.
A string tuned from standard tuning to 4 half-steps lower has a tension 63% of the original tension1. The increased scale length at 26.5 inches increases the tension by about 8%2. The net tension is thus 63% x 108% = 68%.
Leo Kottke said he typically tunes his 12 strings to C#. Here’s a table of how detuning 3-half-steps from standard tuning affects tension on a 12 string guitar using D’Addario EXP-38 strings (the strings that came installed on my Breedlove).
|String||Note||Freq||Tension EXP38||New Note||New Freq||Change in Tension||Tension|
Some interesting statistics on why to de-tune your 12-string from standard tuning: If you look at what the tension would have been if this were a six-string guitar by looking only at the odd numbered strings (the first string of each pair) we can calculate the six string tension would have been 129.21 lbs. The tension for the 12-string isn’t quite double, but nearly so (190% higher than the six-string tension). Remember, four of the paired strings are an octave higher in pitch on a 12-string. By de-tuning to C#, the tension is reduced to only 134% higher than the six-string tension.
I had originally tuned my 12-string down to a C (4 half-steps lower than standard tuning). I loved the deeper sound with the guitar tuned so low. The reduced tension also made playing almost as easy as on my electric or classical guitars. I could do jazz chords in the fifth position with no effort. But the trade-off is obviously the individual string tensions are now so low that buzzing is inevitable. Either you learn to live and love that sound or you tune up until you’re happy with the sound. Tensions under about 14 pounds are going to a problem. I have since tuned to C# for standard tuning, the same as Leo. That gave less buzzing and is still reasonable for ease of playing.
The next subject, alternate tunings for twelve-string guitar, also deals with string tensions. Essentially, any alternate tuning you might use on a six-string can be applied to a twelve-string guitar with the understanding you will tune the lower four strings in octaves and the highest two strings in unison. The more important thing is to remember you don’t need to tune to open D or open G or any other alternate tuning using the same pitches you do on a six-string. Instead, you can lower those tunings by several steps, unless you enjoy the higher tension.
Here are some statistics on how this affects tuning. Starting with the twelve-string in standard tuning and tuning to Open D, the average change in tension over 12 strings is 88%. Retuning from standard 12-string tuning to Open G results on almost no overall change. The average tension of the strings is 97% of what you started with.
If we detune from Open D to Open D -1 or Open C#, the average tension is reduced by another 10% to 78% of Standard tuning tension. Detuning from Open G to Open F, two half-steps down from Open G, the average tension is 77%, not much different from Open C# (D -1). The trade-off for these lower tensions is the same as with standard. Some strings may have too little tension to not flop around against the frets causing buzzing.
- The formula for calculating the change in tension when a string is tuned to a different note is (New Frequency in Hz)^2/(Original Frequency in Hz)^2. If you know the original tension you can multiply it by the result to get the new tension. Otherwise, the result is the ratio of the change.
- The formula for how a change in length of a string affects tension is similar to frequency. It is the square of the new length divided by the square of the old length. It doesn’t matter what units of measure you use for the string length as long as new and old are the same units. The result, as above, is a ratio, or if you multiply by 100, a percent. If you know the actual starting tension, you can multiply the result by the tension to get the new value.