View Bass reflex port
To work around the performance bottleneck of a small speaker cabinet and drivers, bass reflex port can be added to enhance low-frequency delivery. This is installed either on the front or the rear, and comes in single- or multiple-port configuration.
A catch for such a design versus a sealed cabinet is the possibility of port noise. This is often a result of poor implementation which can lead to compromised sound quality. Rear ported speakers also tend to complicate installation with sufficient space clearance a prerequisite for nimble tight bass.