To Doug Schneider,
I have one pre-out from my Denon AVR-4311 and two inputs on my sub. Should I use a single mono cable or a “Y” cable to connect to the sub? What's the difference between them?
Providing they’re both inputs of the subwoofer (and one is not an output for connecting one subwoofer to another in series), chances are they are for the left and right channels, which is irrelevant in your case because your AVR-4311 has one mono subwoofer output. Where left and right inputs would be relevant is if you’re connecting the sub to, say, the left and right line-level outputs of a stereo preamplifier.
Insofar as connecting your receiver to the sub, you’d be better off to look at what the owner’s manual says first. They might recommend using a specific input or there might be suggestions on how best to hook up a single-output receiver -- not every subwoofer out there is the same, and the configurations of some of them can vary quite substantially. But if you don’t have access to the manual, or it doesn’t say explicitly how to hook it up, I suggest running just a single wire and see how that works. Chances are you’ll probably have to put the sub’s volume control about 3dB higher because only one input is active and not two, but that shouldn’t degrade sound quality. . . . Doug Schneider