sealed & ported boxes?
Better car audio, Tip #5: Build or buy a better subwoofer box
The quality of the bass you get from your component subwoofer doesn't depend on the woofer alone. You'll need a strong, tightly-constructed enclosure for optimum subwoofer performance.
If you're building a sealed box, make sure it's sealed up tight. Air leaks can really hurt your sub's performance. If you're using a ported box, make sure you've got the right sub in there. You can destroy a sub that's designed for sealed box use by driving it hard in a ported enclosure. Also, it's important to build a box with the correct interior volume and port dimension for the sub you've picked out. A mismatch can result in poor performance or a sub fatality.
You can also avoid all of these issues by buying a premade or ready-to-assemble enclosure that'll work with your subwoofer.
This post is excerpted from a recent article in our Learning Center, Jeff's Tips for Getting Maximum Sound Quality in Your Car.