3ed11/9
← 2ed11/9 | 3ed11/9 | 4ed11/9 → |
(semiconvergent)
(semiconvergent)
3 equal divisions of 11/9 (abbreviated 3ed11/9) is a nonoctave tuning system that divides the interval of 11/9 into 3 equal parts of about 116 ¢ each. Each step represents a frequency ratio of (11/9)1/3, or the 3rd root of 11/9.
11 steps of this temperament is an extremely close approximation of 9²:13², having only 0.5% relative error. 6 steps is exactly 9²:11² (since 3 steps is 9:11), so 9²:11²:13² (81:121:169) is well approximated, which represents the approximate 2:3:4 created by overtones of chimes.[1]
9²:11²:13²:17²:23² is also very well approximated.
Approximation of odd square harmonics relative to 9²
ratio | steps | relative error | absolute error
1²:9² | -66 | -30.4% | -35.2¢
3²:9² | -33 | -15.2% | -17.6¢
5²:9² | -18 | -42.5% | -49.3¢
7²:9² | -8 | -48.6% | -56.3¢
9²:9² | 0 | 0% | 0¢
11²:9² | 6 | 0% | 0¢
13²:9² | 11 | -0.51% | -0.59¢
15²:9² | 15 | -27.4% | -32.1¢
17²:9² | 19 | -1.6% | -1.8¢
19²:9² | 22 | -34.2% | -39.5¢
21²:9² | 25 | -33.4% | -38.7¢
23²:9² | 28 | -5.4% | -6.3¢
9ed11/9 is a possible correction for 15, 19, and 21.