Philsie

I have the Klipsch R12SW and a recent behavior with the AUTO/ON/OFF has me concerned either about the SW or the Pioneer receiver. When I turn off the receiver lately, after about 15-20 seconds I begin hearing a low hum from my R12SW. I also have an R10SW in the other LFE that does NOT do this. The result is that the SW does NOT auto turn-off like it used to. I noticed that if I unplug the LFE line in from the speaker the hum stops and presumably the SW will eventually auto-OFF (but who has 20 minutes to wait for that). So either the receiver is still pushing signal down the LFE when it's off or the SW thinks there is. I tried moving the outlet used by sub to one further away to rule that out. If it tap the LFE line to the port the sound seems like feedback speaker hum. Any thoughts on how to isolate or correct this?