Ai41/Ai60/Ai61/Ai81: How to connect a subwoofer
To connect your subwoofer to the powered speakers, connect the SUB OUT connection on the Active Speaker, to the LFE/Low-Level Input on the subwoofer. Adjust the subwoofer's Crossover Frequency to 80Hz (the crossover point when a subwoofer is connected to the speakers), and adjust as necessary.