In the middle of the 1970s, particularly on the West Coast, dead was in, especially when it came to recording drums. The mindset at the time was to throw as many blankets and carpets as possible in the tracking room, put towels on (and in) the drums, and generally control the recording through absorption. The idea was to null as much of the reverberant energy as possible to make the recording sound more articulate (meaning each instrument was clearly audible in the recording), but the result was some incredibly dry and dead sounding records. Producers and engineers were experimenting, and well, sometimes experiments don’t turn out too well.

Unfortunately, a lot of that mindset has survived and continues to wreak havoc for AV enthusiasts to this day.

 

Here’s the rub: the recording you will be listening to will generally carry the reverberation signature of the room it was recorded in (concert hall, recording studio) for music and in the case of a movie the recording will carry the reverberation signature of the scene the director and audio designer conjured up. The reverberation has been provided for you by the program, so it stands to reason that a room that is overly reverberant will interfere with the audio playback as it was intended.

 

So you should design your room to be as sonically dead as possible, right?

 

Not really.

 

It’s All About Early Reflections

Sit in your chair in your prime listening position and look at your speakers (L-C-R), then look at the walls to your left and right. Somewhere along that wall the direct sound from the speaker bounces off the wall (below) before arriving at your ears. This is called the first lateral reflection.

Early Reflections

It’s important to remember that there is a different early reflection point for every possible seating position in the room. Also keep in mind that there are four first reflection points for every seating position: the two walls, the floor and the ceiling. Floor reflections are very rarely a problem because of the angle they arrive from (they typically arrive too late and too weak to interfere with the direct sound). In studies of concert halls around the world, researchers found that audiences generally find the sound more desirable in a room where the reflections from the ceiling arrive more than 20 milliseconds after the lateral reflections. That’s fine for a room with a 20-foot (or higher) ceiling, but in your house, it’s probably better to null the first reflection from the ceiling because it's going to arrive at your ears way quicker than that. In fact, go ahead and null the first lateral reflections as well and let the program you are listening to provide the sense of reflections.

 

This is the long way to letting you know that you should null off the reflections in the first third of your home theater with absorptive material. By using absorption in the first third of the room you are pretty much ensuring that every listening position will be as free as possible from interference from first reflections. In a concert hall those reflections give a sense of intimacy or space (depending on the design of the room), but in your much, much smaller listening space those reflections only serve to muddy up the sound.

 

If you are designing a room specifically for listening to music, use the mirror method to find the first reflection for your listening position and treat that specific area, leaving the rest minimally treated. Sit in your listening position and have a friend move a mirror along the lateral walls (and the ceiling too!). When you see the speaker in the mirror you will have found the first reflection point.

 

Skip the Glass-Framed Picture, Hang the Velvet Elvis Instead

Because you will more than likely need a place to sit, some curtains on the windows, a painting or picture or two, a carpet, some lights, Velvet Elvistables and other assorted bric-a-brac, you will also be treating your room with absorptive (or diffusive) material by default. The things you put in a room play a big role in how a room will sound, so try to keep the reflective decorations to a minimum in that all-important first third of the room. In a home theater and to a lesser extent a dedicated music room, you really can’t over absorb (in the first third of the room) including the area behind the screen or television (the front of the room), but one unfortunately placed mirror can (and will) mess with how your system sounds!

 

The most often overlooked aspect of room design is the stuff you put in your room and you will be shocked and dismayed at how much trouble you can cause yourself.