According to different sound principles and internal structure, car speakers cabinet can be divided into vented, closed, flatbed, horn, labyrinth and other types, the most important form is closed and vented. Closed box is that installed speaker in a closed box, efficiency is lower. The difference of vented car sbwoofer enclosure is circular hole equipped in the front or rear panel of the inverter. It is based on the Helmholtz resonator principle to work, the advantages of high sensitivity, can withstand greater power and dynamic range.
Because the sound waves released from the guide hole, so its efficiency is higher than the closed box. And only one speaker mounted in a suitable inverter box will be higher than installed in the same volume closed box. That is good for the low-frequency part of the performance, so this is the important reasons that inverter box is widespread.