I left the response curve picture full size to preserve the detail, the link is below. method: burned sine tones from NCH generator, 1Hz steps, 1-85Hz. red line is 70dB/60Hz baseline. utilized radio shack analog dB meter (stock) played tones in 1 hz steps, starting at 85hz working down (allowing 10 min cooldown after each 10 steps, just to be careful) and charted results in 1Hz steps. note that after baseline was set meter was moved to new location, and left for duration of test, hence -5dB reading at 60Hz. results here i have suspicisions the null at 67hz may be due to meter placement, i may retest another day when i have more time.