Here’s a pic.
I only mean to introduce this as an option. I learned it here, myself. For me, the main thing I got from it was that my Auto-On feature worked more consistently than it did with just the single LFE feed.
I’ve seen references to the decibel gain that Lovin’ mentioned above, but even now didn’t see anything on a quick internet search. Moreover, I don’t recall ever needing to adjust my gain down after doing this in terms of running Audyssey. But then, I also turn my subs down a little after Audyssey because they run a little too hot for most music I listen too.
Regardless, this was only in response to your comment about which input to plug into:

if one is labeled LFE (usually I think it’s the ‘right’ channel, either one can/should work, or both.
Cheers!
Sent from a handheld device using a silly little app.