Vented Enclosure
A type of loudspeaker enclosure where the woofer is mounted in an enclosed box except for one vent or port connecting to the outside air space. Vented enclosures feature a lower F3 point than a sealed box for the same woofer. The lower F3 comes at the expense of a steeper low-frequency roll-off. In a vented enclosure, the driver excursion is at a minimum at the box tuning frequency, and increases dramatically below this. Care must be taken to prevent over-excursion (unloading) of the woofer at frequencies below the tuning frequency.