Subwoofers add the extra bass energy that take a party from being good to great. In the wold of subwoofers, the bigger, the better! Subwoofers can be as small as a 10" woofer all the way up to 21" behemoths. Subwoofers can be powered or unpowered, and can be used singly or in combinations. In general, musicans and DJs typically consider 15" ro 18" subwoofers that combine impressive output and ease of transportability.