Is there a built-in low-pass filter?
You probably don’t want your low-mid frequencies reproduced by both the full-range cabinets and the subwoofers as it will tend to create a “hump” in the overall frequency response in that range (although some people like that sound). The ideal solution is to employ an active (i.e. electronic) crossover and power the subs with a separate amplifier. But that can be expensive hence some subs come with a built-in passive filter which prevents them from reproducing anything above the low frequency range. This is called a low-pass filter, not to be confused with a crossover which some subs may feature but not many. In either case the feature lets you power both subs and full-range cabinets with the same amplifier and without the need for active filtering. This passive filtering is a great feature for small to medium club systems, but don’t expect to find it in high-powered subwoofers. The high-power copper coil inductors would have to be huge causing the sub to be even more heavy and expensi
