If I understand correctly, you want to feed 2 outputs (HDTV and receiver) to one input on the subwoofer...correct?
That's something you're going to want to avoid doing for a number of reasons. One big reason is that you're likely to introduce some distortion since the signals won't be matched, not to mention there will be an electrical impedence mismatch. The subwoofer won't automatically block one signal and pass the other. Also the signal from one output would be fed into the output of the other, and you could end up damaging a component.
So unless you have some kind of switch for each output, keep just one LFE input to your subwoofer.
I have new sub woofer which I am setting up to my surround sound system. It offers 3 options for set up.
Option 1. Use the LFE source from my receiver.
Option 2. Use front left/right speaker level source.
Option 3. Use the signal output from my HDTV monitor(connects to the sub LFE).
I am currently using Option 3 and it works good.
My question is, can I set up my sub with both Option 3 and Option 2 simultaniously?
This way if I don't want to use the receiver, only the HDTV, the sub will operate. But, if do use the receviever the sub will have two sources. Will it pass one signal and block the other to work properly?