Product Highlights:Sealed EnclosureThe NVX XMDFS121 has a sealed subwoofer enclosure design. This means that the air is contained and does not enter or exit the box. This creates a tighter more accurate sound than a ported or vented enclosure. Because a sealed enclosure is competing less with air the subwoofer enclosure tends to have a better transient response which allows the system to respond more quickly to sudden changes. A sealed enclosure also offers improved acoustic suspension and con