Bass-reflex Enclosures

A bass-reflex subwoofer adds a port to the enclosure: a tuned tube that resonates the air inside the cabinet and makes it work with the driver cone. Below the tuning frequency, this port radiates bass to reinforce the loudspeaker, allowing it to extend lower and deliver more output than a sealed subwoofer of equivalent size. This is the most widespread design, especially for home theater, where the physical impact of explosions, rumbles, and the effects channel matters as much as refinement. The efficiency gain comes with an accepted trade-off. Near the tuning frequency, air movement in the port can color the bass, and below this frequency the cone is lightly loaded, resulting in a steeper roll-off slope and less linear phase behavior than a sealed subwoofer. The result is generous, enveloping bass, sometimes a little less tight on the fastest transients. The diameter and length of the port determine the tuning, and some models include plugs to close it and restore operation close to that of a sealed enclosure depending on the room. Placement requires attention: a port too close to a wall or corner reinforces the bass and can make it heavy. This subwoofer is part of the full range of subwoofers, enhances the bass of a soundbar or a home theater system, and connects to the amplifier via a subwoofer cable.