There are basicaly three types of box for your subs..
1 sealed, this is as it said sealed
2 ported, this is a sealed box with a tube inserted, venting the air.
the tube or port is tuned to the frequency of the sub by sise and length. Larger the sub, larger the length and opening sise of the port.
3 band pass, this is like having two boxies with the sub fixed in between, the side that the sub playes into is usualy ported.
4 not realy a 4 but you can have all sorts of combinations of the three.
now we all know all about sub boxies. what do they do?
WELL THEY MAKE THE SOUND REAL LOUD!!!!
But you need to know what you are doing to get it to sound any thing like right... Did any one have a look at my setup on the front at Brighton? it doesnt take much power to sound sweet!!