Sealed subwoofer boxes tend to be much smaller than ported enclosures, since they use the air inside the box as a "spring" for the enclosure. If you do not have much space, it would be a good idea to go with a sealed box. Not only is there a size difference, but there is also a difference in sound compared to a ported box. Generally, the larger the box, the lower the tone of the bass achieved. However if the box gets too large, the "spring" effect that the air creates may be lost, losing loudness and crispness. Sealed enclosures produce tight, accurate bass and have a flat frequency response curve. They are the enclosure of choice when quality is the ultimate goal of the system set up.