An easy way to check is to run all your speakers as full range, and connect some speaker wire "speaker level" to your sub from your main amp/speaker posts!!! (so you're not connected via "line level", bur rather "speaker level") I believe your sub has both speaker and line level connections, yes?
IF the sub works, then it's a connection/internal setting problem from the rotel likely. Otherwise, a connection problem at the sub. Another way is to get a nother little sub and try it. If it works, then it's your sub!!!
good luck
IF the sub works, then it's a connection/internal setting problem from the rotel likely. Otherwise, a connection problem at the sub. Another way is to get a nother little sub and try it. If it works, then it's your sub!!!
good luck