Go to Home Depot, or your local flavor of Hardware Warehouse store. Go to the concrete department. Look for the tubular cardboard concrete molds. At Home Depot I bought some in an 8-inch diameter for about $6 each I think. These are heavy cardboard tubes four feet in length - like a huge heavy-duty mailing tube for a poster. You can experiment covering these tubes with various fabric or foam to create your own bass traps. Stack'em, put'em in rows, make'em different colors, collect'em and trade'em with your friends. I used egg-crate foam, which was easily attached to the outside of the tube using a staple gun (adhesives may work too, but the staple gun makes it pretty easy. You can make these as pretty as you like. I buy the denser egg-crate foam (meant for sound applications) from a local foam store. There are some online sources as well. I think the foam to cover one of those tubes was about $20.
Have fun!
Marco
Have fun!
Marco