You have a basement that isn't doing much. And you've been thinking about turning it into a theater, with a big screen, seating built for it, and a room that goes completely dark. 

Most home theaters never get a room of their own. 62% of them sit in a living room or den, sharing space with everything else a family does in a day. Someone runs the dishwasher during the third act. Afternoon sun washes out the picture. Your basement has neither problem. It sits away from the traffic upstairs. And you can close it off and build it around one use. 

A home theater means a screen 50 inches or larger, or a projector, paired with surround sound. That equipment is the visible half of the project. The other half goes in behind the drywall, and it decides whether the visible half holds up. Moisture control, sound isolation, wiring, and airflow all get installed before the first speaker goes on a wall, and they go in a fixed order.