Some people like to use a 1/3rd octave EQ to fine tune their system, creating a perfectly smooth response curve, as well as dialing in time alignment to compensate for the higher frequencies which travel faster. All this effort usually results in a setup that sounds like *** to most listerners. Bouncing the tweeters off the window, creates a natural delay of the frequencies they produce, disperses their sound, making them less harsh, and also broadens the sound stage. None of which can be done by an EQ. In the words of Totalimmortal, "a tweeter that reveals its position is completely useless".