Inpepinnovations...Yes..the small sealed box aspect of the original Bose 901 was an important element of the design. Most speaker designers try to get the resonant frequency of their driver/box down as low as possible. Prof. Bose noted that if you push the resonant frequency the other way, up, (and 200 Hz sounds familiar) the roll-off below resonance, although steep, is very smooth and can be effectively corrected by electronics.
The resulting requirement for a high power amp was the downfall of this design. I assume that the present-day 901
which is vented also has a high resonant frequency, although, as you say, this is more complicated than a simple "too small" sealed box.
The resulting requirement for a high power amp was the downfall of this design. I assume that the present-day 901
which is vented also has a high resonant frequency, although, as you say, this is more complicated than a simple "too small" sealed box.