Here's the latest run using 90dB target level.
4 x 15" IB. REW generator sinewaves: F follows cursor
REW SPL meter readings: 2nd harmonic readings. WYSIWYG
Hz..SPL(REW).2nd%
50.....92.7......0.27
40.....93.5..... 0.4
30.....92.9..... 0.25
25.....93.4..... 0.4
20.....93.6..... 1.3
15.....91.6..... 0.4
10.....91.9..... 0.9
9..... 86.........1.2
8.......80.2......2.3
7.......77.........~3
6..... 74.7......~7
5.......52.......~200 *
*REW repeatedly locked up at 5Hz with loss of test tone.
I had to restart my computer 3 times.