It is not uncommon to have two audio systems in one listening environment. Most frequently, this is a multi-channel home theater system and a stereo, 2-channel system setup in the same room. Often times, using a single subwoofer for both systems is desired.
The managed bass subwoofer output from a home theater receiver or processor and the line outputs from a 2-channel preamplifier or integrated amplifier with line outputs can simultaneously be connected to one subwoofer. Obviously, it is not recommended to play both audio systems at the same time.
JL Audio home subwoofers utilize individually buffered left and right inputs that are internally summed to mono. This allows two separate line-level signals to be connected at the same time.
Additionally, the Gotham® v2 and Fathom® v2 powered subwoofer models include pairs of both balanced XLR inputs and unbalanced RCA inputs. One pair of XLR connections and one pair of RCA connections can also be used simultaneously, as they are also internally summed.