Bose 901 Series II Speakers and Active Equalizer 1973 to 1976 "Antique Walnut"

The unique Direct/Reflecting design of the speaker causes most (89%) of the sound produced to be directed to the rear of the cabinet, away from the seating position. This sound bounces off the back and side walls before reaching you. Depending on your preferences, this is either "Stereo Everywhere" if you like the effect, or "Stereo Nowhere" if you don't care for it.   The use of nine identical 4 1/2 inch drivers, rather than the more traditional "big" woofer, "little" tweeter, and "just right" midrange cones is another design choice. Nine small drivers, acting in unison, have about the same air-moving capacity as a single large woofer and mid-sized midrange cone. On the other hand, it's tough to get a 4 1/2 inch driver to put out high frequencies. And so here is a trade-off. Using multiple, identical drivers allows Bose to totally eliminate a passive crossover network, but instead, a special, purpose-built Active Equalizer is needed to extend the frequency response of the speaker unit.