JL audio makes W7 series subwoofers to be the loudest, and their speaker series to sound the cleanest.  But what good is a subwoofer without an enclosure to put it in.  The JL audio subwoofer boxes come loaded with JL W1, W3, or W7 subwoofers in single or dual.  The subwoofer enclosures from JL are designed to perfectly match each subwoofer, including: mounting depth, air space, frequency, and box thickness.  You can take one of these JL Audio boxes drop it in a vehicle, hook an amp up and you will instantly have head pounding bass.