The distance from the subs to the hatch to the subs is directly cancelling in the bandwidth. The reflected wave is cancelling the original wave. Hence when he opens it the cancellation goes away. Move the subs 4-8 inches from the hatch and it will sound better.100% but I think it depends on the overall application and not just being in phase. Almost all the big 4th,5th,6th order builds have subs firing at each other