Bud, except in nearly square rooms the best location for a single sub, as Dr.Toole, Tom Nousaine and other researchers have pointed out, is usually the corner farthest from a large opening. If you're going to install multiple wall plates, as Randy commented you might want to consider eight, one in each corner and one at the midpoint of each wall.

Last, and hopefully not too pedantic a point, "RCA" refers only to the connectors at the ends, not the cable itself, which is most commonly a coaxial cable.

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Enjoy the music, not the equipment.