The Tremor-18 Powered 18 Inch Subwoofer Cabinet is our most affordable and thus, top selling powered subwoofer. It is a great active sub for both the novice and seasoned musician and DJ. As you can imagine, we field a lot of questions about the features of this subwoofer. Continuing our endeavor of excellent customer service, we put together a list of the top 10 things you should know both before and after you purchase a Seismic Audio Tremor-18 Powered 18 Inch Subwoofer Cabinet. Enjoy this handy resource and as always, if you have a question, please give us a call!