The sound wave coming off the back of your subwoofer reacts with the air contained in the box. Poly-Fill stuffing slows down sound waves inside the box, making the subwoofer perform as if the box were bigger. Use 1 to 1-1/2 pounds of Poly-Fill per cubic foot of box volume.

Q: What's Poly-Fill and how will it affect my subwoofer's sound?

A: You're probably already familiar with Dacron polyester fiber-fill, or Poly-Fill — chances are you've slept on a pillow stuffed with this material. But you may not realize how Poly-Fill can help your bass.

Stuffing your enclosure with the right amount of Poly-Fill can make your box behave like it's larger than it really is. This comes in handy if the volume of the box you've built turns out to be a hair shy of the cubic air space recommended for your subwoofer. Depending on how much Poly-Fill you use, you can actually vary perceived box volume by as much as 30%.

You can also "stuff it" if you simply don't have room in your vehicle for the larger box your sub demands. And adding Poly-Fill to any enclosure can clean up your bass by minimizing unwanted box resonances — and at a reasonable cost.