Is this a single subwoofer? What are the dimensions of your room and how much air goes in and out of the room or into a next room for example. It looks like it could be exciting some room modes but how close is the subwoofer to a wall? Is the subwoofer on the side wall between the front wall and the seating? Which subwoofer is this? I will try some searching to see what info I can find on your setup.