Null, node; these phenomena are caused by standing waves in the room. A standing wave in this case is where a bass note is so long that it is able to reflect off of the wall behind you and cancel itself.
No matter what anyone says this cannot be cured by room treatment using bass traps or room correction using Digital Signal Processing (DSP). In the case of the latter, the cancellation means that you can put nearly infinite power with the same result until the wall behind you collapses. With the former, to be effective the bass traps need to dynamically move about the room as the bass notes change.
The more elegant solution is to use multiple subwoofers arranged asymmetrically in the room. This breaks up the standing waves and you get evenly distributed bass. The trick is to make sure the subs don't go above about 80Hz so as to not attract attention to themselves. Then the main speakers will convince you that the bass notes are coming from them. Audiokinesis.com makes a sub called the Swarm that is meant specifically for this use; its one of the very few I've seen that is designed to be as close to the wall as you can get it and still be flat (to 20Hz), and they are not crazy money.
No matter what anyone says this cannot be cured by room treatment using bass traps or room correction using Digital Signal Processing (DSP). In the case of the latter, the cancellation means that you can put nearly infinite power with the same result until the wall behind you collapses. With the former, to be effective the bass traps need to dynamically move about the room as the bass notes change.
The more elegant solution is to use multiple subwoofers arranged asymmetrically in the room. This breaks up the standing waves and you get evenly distributed bass. The trick is to make sure the subs don't go above about 80Hz so as to not attract attention to themselves. Then the main speakers will convince you that the bass notes are coming from them. Audiokinesis.com makes a sub called the Swarm that is meant specifically for this use; its one of the very few I've seen that is designed to be as close to the wall as you can get it and still be flat (to 20Hz), and they are not crazy money.