I have a 2012 36RL and they plug into the back of my LG receiver. You should see the wires in the middle glass front cabinet over the TV. I personally just put a sound bar in just below the TV as I did not care for the sound quality of the OEM system.
Dean & Cindy (Go DAWGS)
2013 Ram 3500 CC DRW 4.10 "Plain Jane"
(RIP "Struck by Lightning")
B&W 3600 Hitch 25K/6.25k
2012 36RL, Disc Brakes, G614's, 7K axles, Combo WD, Awning Toppers
Full Time Since April 1 2015:)!