Finished my sonotube subwoofer with an 8.9 cu ft enclosure and tuned to 17 hz. Modeled using WinISD and "Non-Boomy". I needed something to play having deep base, so I downloaded an 1812 Overture MP3. If you remember the cannons fire at the end of the symphony you could realize the power of my new subwoofer. Boom.... puff, up blows my window curtain, Boom again and again.... puff.... puff, up blows the window curtain again. We had to laugh. Worth the money. Next, we played "Black Hawk Down". The choppers seemed to circling overhead and around the room. Great sound. Anyone in Philadelphia area interested in buying remaining 20" sonotube, contact me.