Another key specification to focus on, however, is volume requirements. Car audio subwoofers all come with recommended volume requirements for sealed and ported subwoofer boxes alike. For example, let's say you scored a JL Audio 13W7, one of the most coveted car audio subwoofers on the market. Essentially, it's not enough to find a subwoofer that fits based on size and power alone. Of course, a subwoofer won't fix all your audio needs, and you may want to explore other ways to improve your car audio.