Both subwoofers must be connected to your AV receiver. This is the easiest part. The trickiest part is aligning them to achieve the best low-frequency response possible without getting any phase cancelation issues. To do this, you have to measure your room and account for delay times because the sound of one subwoofer will inevitably reach your ears before the sound of the other does. To solve this problem, many AV receivers have a feature called delay time adjustment, where you can delay the sound signal by a few milliseconds. This technology makes a huge difference in the overall sound quality.