How to Build a Media Room

Posted 06/12/2007 at 12:48pm | by Michael Brown

6

Comments

Print

A room with parallel reflective surfaces—and that’s just about any room—will create a phenomenon known as standing waves. Standing waves are created when sound waves are reflected back and forth between two walls or between the floor and the ceiling. The sound waves travel across the room, bounce off the opposite wall, and encounter the identical sound waves emanating from the speakers, cancelling each other out. Standing waves distort bass and lower midrange frequencies.

One way to reduce the prevalence of standing waves is to eliminate parallel surfaces. I didn’t want to go so far as to slope the floor or ceiling, and I didn’t want to create a crooked wall (remember, this is a house), so I created a room within a room. The room’s exterior shell is framed with 2x6 studs, but I had the carpenters nail down a second top and bottom plate about an inch away from the first with 2x4 studs to form an independent wall. This second wall is canted by about two degrees from the first, so that the room’s front and back walls are no longer parallel.

Canting the north wall by two degrees should reduce problems with standing waves.

This construction provided more than eight inches of dead space between the inner and outer layers of sheetrock, which we filled with two layers of R19 fiberglass insulation. I then had the drywall hangers apply two layers of half-inch sheetrock to the interior walls and ceiling, with a layer of acoustic sealant squeezed between them for good measure. Since room-within-a-room design created an extra deep doorway, I’m going to install two solid-core interior doors to further seal the room from the rest of the house (one door will open out into the hallway and the other will open into the room).

If you build a room within a room, make sure the studs don't touch each other. This will prevent the sound waves from traveling through the wood.

The house isn’t finished yet, so I don’t yet know how soundproof the room is ultimately going to be, but I do know that it’s already remarkably isolated: You can literally hear the difference when you walk from the foyer into the room; it’s almost as if there’s a difference in the air pressure. There are any number of other things I could have done to soundproof the room even further, but I didn’t have an unlimited budget to work with.

Several factors also remain unknown at this point. I’m having my cabinetmaker build a custom entertainment center at the north end of the room, and I’ll be hanging heavy curtains over the windows (glass is a highly reflective surface). The wooden cabinet will reflect more sound than the drywall, but the cabinet will reach from the floor the ceiling, so the surface will be somewhat uniform.

Update:  Here's how the finished product looks.