Subwoofers are designed to represent the bass frequencies from your music. However, they also relieve the low-end burden on woofers and mid-bass by applying earlier low-pass filters to those speakers and allow them to play to their intended frequency range.
The JL Audio 13TW5v2 - 13.5 In Subwoofer uses Thin-Line technology to compress the architecture using a “concentric tube” structure that supports the 7-inch diameter voice coil and the suspension attachments....