In this tutorial, we learn how to build a subwoofer out of cardboard. You will need to buy SonoTube, which is giant cardboard tubing. It comes in a variety of different sizes, so you can find one that will be around the same size as your subwoofer. To make the casing, you will need to use a saw to cut the tube to the size you need. Make it a snug size, but make sure it's not too small or you will have to start all over again. Use caulk and glue to stop any leaking air from getting out of your subwoofer. When finished, enjoy your subwoofer without paying a ton for it!