Green light at the back of my Pro linear FB950 Subwoofer turns Red after playing for about 10m. I powered off and ON but the sub does the samme problem. My Amp is Onkyo TX-NR609

SOURCE: SUBWOOFER NOT WORKING?

if you have real old wires from the amp to the sub try getting new wires on it. check the little wires that go to the cone itself on the sub. sometimes they can manage to get pulled out of their terminals and make sure that thier touching the terminals on the correct spot

SOURCE: Onkyo Subwoofer Pre Out Problem

May not necessarily be the out put, discontect the sub from the receiver and see if it still makes a hum, Making sure that you turn auto on, off on the sub woffer.
If it still makes a hum, then you have a earthing problem, you can get a earth filter put on your internal wiring in your home, or you can remove the earth pin on your sub woffer

SOURCE: very low ouput from subwoofer preout

Onkyo to Onkyo, sub/receiver, problem fixed by inceasing volume on receiver. Seems the sub audio input does not pick up LF's below a certain output level from the receiver. So, guess I have to live with that. I only hope my nieghbor in the apartment below me can too!

SOURCE: no signal on subwoofer out in Onkyo TX-SR703(E) - similar to TX-SR803

Hey Tad, I have the same problem and perhaps a solution. I just moved to the other SW "pre-out" and it seems to be working..the green light is on . Whatever works i guess.

SOURCE: Onkyo 805 sub hook up problem

I made the same mistake when i hooked my REL sub up to the back of the 805.

The problem is there are 2 connectors on the back of the amp that are labeled as sub out. Look very closely, you will see that there are 2 grouped RCA outs. The RCA out group you are looking for differentiated by groups of "little white dots" all the way to the far right on the back of the amp. Hope this helps.