Bassrefleksi

Bassrefleksi, or bass-reflex, is a type of loudspeaker enclosure that uses a port or vent to enhance low‑frequency response. The woofer is mounted in a cabinet with an opening that connects to the outside air through a tuned port. The air in the cabinet and the air in the port form a Helmholtz resonator, and at the tuning frequency the port’s output adds in phase with the woofer, boosting bass output without needing a larger box.

Key parameters in a bass-reflex design are the cabinet volume, the port diameter and length, and the tuning frequency (Fb). The tuning is chosen so that the port reinforces frequencies below the driver's natural roll-off, typically extending usable bass into the 20–40 Hz range for many designs. The overall response depends on the driver, enclosure integrity, port design, and how the system interacts with the listening room.

Benefits of bass-reflex enclosures include increased bass extension and higher efficiency for a given cabinet size, compared with sealed designs. Trade-offs can include less precise transient response and potential bass “boom” if the tuning is poorly chosen. Port noise, such as chuffing at high levels, and sensitivity to air leaks or obstructed ports are practical concerns. Proper construction and damping, along with careful placement, help mitigate these issues.

Placement and room interaction are important: placing the speaker near walls can boost bass, while room modes can cause peaks and dips. Alternatives to bass-reflex enclosures include sealed (acoustic suspension), transmission line, and horn designs, each with its own balance of bass extension, transient response, and efficiency.