Having this same issue with my A3000 + Klipsch SW-450. Trying to narrow the issue with either the receiver or the sub. Setup has worked previously for a few months.
After an effort to clean up the rats nest of wires behind the tv stand, I noticed the sub wasn't doing anything. After looking noticed the sub connection was in the subwoofer input rather than the preout. Though even after switching it back to the correct connection it still doesn't work.
Tried swapping my subwoofer cable with another cable. Even tried switching to the 'Front' subwoofer preout but to no prevail. I can ground out the subwoofer wire against something metal and the sub will sound off but that's the only time it will work. Any suggestions?
ended up calling Klipsch, they diagnosed it as a bad amplifier in the sub. After playing with the settings in my reciever, I cranked up the gain on the subwoofer to +10dB (highest it would go) and finally could feel the sub doing something but still not right.
After digging through the manual, I have finally figured out why my subwoofer does not make sound when listening to music without any surround sound processing - you have to activate "extra bass" feature under manual speaker setup (scroll down past subwoofer setting all the way to the next screen) - when "extra bass" is on the low frequency is played through both the front speaker and subwoofer; when "extra bass" is off then subwoofer does not engage if you set front speaker to large. However when you turn on any surround mode then the subwoofer will be used no matter if "extra bass" is on or off.