The TRx3018A is an 18-inch powered subwoofer that is considered the finest subwoofer made by Carvin. Subwoofer has only been used for less than a half-dozen shows and is truly in like-new condition. The only reason why my band is selling it is because we initially bought 2 of these subs and found we are able to get all the low-end punch we need by using only one. This decision was made after playing our last show for over 500 people, to give you an idea of their sound output capabilities in a large venue. It features an additional amplifier output that allows you to connect and run power to a top cabinet main speaker. Subwoofer comes factory programmed with optimized presets that can be used with several different models of Carvin speakers. Don't have a Carvin speaker to connect to the sub? Simply go to the "Variable X-Over" preset and select the crossover frequency and you'll be able to connect and use whatever type of main speaker cabinet you have. Don't need to connect and power a main speaker? All you have to do is go to the "Sub only" preset and select the crossover frequency for the sub and you'll be all set. The TRx3018A features foot locating holes on top of the sub to allow you to attach any standard 1-3/8th pole mounted equipped speaker cabinet system. Made in the USA. Feel free to email me if you have any other specific questions about the sub. Price does not include shipping costs.