I found these Bose speakers at a garage sale this past weekend and I thought that the method of adjusting the tweeter response was amusing, yet ingenious. “Direct Energy Control”! I wonder what the equivalent would be for woofers and subwoofers!
Unfortunately, I forgot to take a picture of the knob, which was notched and had a word or two to describe the resulting adjustment sound.
(I sincerely apologize for the fuzzy photos.)