With the output of a folded bass horn, this is one of our most impressive subwoofers ever. Powered by a 1300W amp and partnered with one of the most powerful subwoofers made, it literally ripped apart our first prototype test box. This sub is designed to have high output down to the mid 30 Hz Range. Perfect response with such a low frequency from a box of this size is rare in the industry. The 21” woofer sounds like an overly massive 15” woofer , tight and quick, but with incredible low end. This subwoofer is absolutely amazing. You have to hear it and feel the bass shake you to truly understand.