What is meant by subwoofer room pressurization?

What's the point of subs if they are set so they are not observable sources of sound? I set my subs so they blend seamlessly with my main speakers.

Hew,

Not observable and seamless mean the same thing to me. I aim for a soundstage in which the listener is unaware of any speaker, just fine imaging within the soundstage.

db

Some say that when a wave is unable to unfold that it 'feeds back' on itself. Thus pressurising the rooms' volumn. I think the frequency is about 150 hz for a big room to 350 hz for a small room.

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.