What is meant by subwoofer room pressurization?

OK, I don't care about movies; I thought it might be an important concept for stereo listening.

Thanks all.

I purchased two 15" subs. I first placed both them on either side of my equipment cabinet facing the audience. I was very disappointed in the impact, so I started reading the sub manual and tried different placement layouts. To get the pressurization effect you're talking about I placed one in the front facing the audience and the other at the back on the opposite side of the room. Now I have bass air pressure coming together right at the point of the seating.

It's a sonic boom... like night and day. The room has become a music chamber and the sound of explosions is unreal. The entire house shakes... the sound is better than a movie theatre.

That happens when the frequency produced by the sub has a longer wavelength than the room can support along any of its dimensions. Usually this occurs below 100Hz (11' wavelength).