There are two (2) SUBWOOFER pre-outs on the rear of the unit. You will need a self-powered subwoofer (they come in a variety of sizes and power outputs!) for this and an RCA type connector cable (all of my new subs came with a cable in their box) that has one male end plug for the AVR subwoofer output and either one or two male end plugs for the input on the subwoofer(s). Once installed, go into your AVR's menu to set up for the subwoofer(s). It really is easy to do and as I said, you can hook up two subs (again, if you unit has two!) if that is something you desire. I have two 10 inch subs on my home theater setup from my Denon AVR-X4300H that I bought at my local Best Buy a couple of years ago (Two 10 inch subs!) For my new Denon AVR-S660H I am using a Martin-Logan 10 inch Sub that I also bought a few years ago at Best Buy and it works great with this AVR. All the best!
SSSS