It’s all about reflections and cancelations. A pebble dropped in the center of the pool creates a uniform wave pattern. A pebble dropped close to the side creates cancelations and a confused wave pattern. Stand behind your speaker, can you still hear the music?
My issue is the bass sounds so much better when I stand up. I’m pretty sure it’s floor reflection but don’t know how to correct it. My subs are stacked so the top sub center of the driver is about 34" and both are pulled out from the wall about the same 34" to the front of the cabinet. It’s almost 30’ to the back wall so I don't think that's where the issue is.