The BPS Active In-Room Subwoofers feature a LFE (Low Frequency Effects) input, stereo/mono line level audio input that can receive full band audio from any audio amplifier, and also stereo speaker level input. Amplified stereo audio will pass through unprocessed to a pair of connected stereo speakers using the speaker high level outs. The signal from the speaker level input will also be processed by the crossover and volume controls to enhance and optimize low frequency content.