We sell a ton of these active 18 inch subwoofers and 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 8 things you should know both before and after you purchase a Seismic Audio Aftershock-18 Powered 18 Inch Subwoofer Cabinet. Enjoy this handy resource and as always, if you have a question, please give us a call!