The terminology "active" and "passive" have gotten all mixed up. "Active" generally refers to a subwoofer that includes a built-in amplifier. "Passive" ought to describe a subwoofer that is driven through a passive crossover network by the same amplifier that powers the main speakers. However, a subwoofer that is driven by a dedicated amplifier with electronic crossover is also "active" even if the amplifier is not physically inside the subwoofer enclosure.
The Active/Passive discussion is really about the type of crossover being used. Passive crossovers at the frequency used for subwoofers involve inductor and capacitor values that are very costly. Electronic crossovers are much more practical at subwoofer frequency.
The Active/Passive discussion is really about the type of crossover being used. Passive crossovers at the frequency used for subwoofers involve inductor and capacitor values that are very costly. Electronic crossovers are much more practical at subwoofer frequency.