Jovan StosicA bass reflex system (also known as a ported, vented box or reflex port) is a type ofloudspeaker enclosure that uses a port (hole) or vent cut into the cabinet and a section of tubing or pipe affixed to the port. This port enables the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical closed box (sealed-box) loudspeaker or an infinite baffle mounting.
A reflex port is the distinctive feature of this popular enclosure type. The design approach enhances the reproduction of the lowest frequencies generated by the woofer or subwoofer. The port generally consists of one or more tubes or pipes mounted in the front (baffle) or rear face of the enclosure. Depending on the exact relationship between driver parameters, the enclosure volume (and filling if any), and the tube cross-section and length, the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure.
Though helpful with improving efficiency, bass reflex cabinets can have poor transientresponse compared to sealed enclosures at frequencies near the lower limit of performance, causing “smearing” or a longer resonance of the bass notes. Proper adjustment (“tuning”) of the cabinet and port size, and matching with driver characteristics can reduce much of this problem.