cross over ....
like ms said............
some subwoofers have either a low pass filter, or a crossover network built into them to take care of the signal routing.
just to be sure you understand what each do:
a low pass filter let you put a full range input into the cabinet, and only lets the ""LOW"" frequencies pass on to the speaker. If this is the case, you simply paralell a feed from one of the monitors into the sub cabinet input.
a crossover network inside the sub works kinda the same, in that it takes the full range signal and divides it up, sending the "lows" to the sub. But they "USUALLY" have an OUTPUT from the crossover sending the mids and highs back out, which you just then plug a cable from the out jack into your monitors. Sometimes these will be marked as "full range" and "bi-amped" inputs with an output (something like that anyway)
should your sub not have either of these, you use what is called a crossover to separate the signals. You will find these as 2 way stereo/3 way mono or some combination like that. The behringer one has a dedicated sub out jack, or you just feed the sub with the low feed, and the other monitors with the high feed. The point where the "low" stops and the "high" starts is adjustable to fit your speakers system.
hope this helps explain a little.
