Well first of all you use four subs, and it hardly matters where they go just that they're not all in the same place.
But anyway regardless of how many or where, the question is how to get the balance right. Its pretty simple. So here's what you do.
First reverse phase so the subwoofer(s) are out of phase with the mains. Now adjust the subwoofer crossover and volume level until you get as little sound as possible in the crossover range. You will probably need to go back and forth a few times, adjusting the crossover and then the level, looking for the best result. When you do, then reverse so they are back in phase again.
Voila!
But I worry that I forgot to mention how important it is that you use four subs. Okay, I see that I did say to use four subs. Whew. What a relief.
But anyway regardless of how many or where, the question is how to get the balance right. Its pretty simple. So here's what you do.
First reverse phase so the subwoofer(s) are out of phase with the mains. Now adjust the subwoofer crossover and volume level until you get as little sound as possible in the crossover range. You will probably need to go back and forth a few times, adjusting the crossover and then the level, looking for the best result. When you do, then reverse so they are back in phase again.
Voila!
But I worry that I forgot to mention how important it is that you use four subs. Okay, I see that I did say to use four subs. Whew. What a relief.