Many home studios are only one room, so the acoustical components of the room must be flexible, compromising between high and low frequency absorption and diffusion.
Every room is different, and artists have different tastes when it comes to their desired sound which effects how much absorption or diffusion the recording space should have. Here is a trick to figuring proper placement of the sound absorbing and diffusing materials: Take a mirror around your recording space and place it against different spots along the walls. If you can see the reflection of the monitors in the mirror, sound waves from the monitor will likely come into contact with that spot as well, and it should have acoustical treatment.
1″ or 2″ thick acoustical wall panels offer great absorption ratings and are more durable than foam, which is important if you are going to be taking them down or moving treatment around for a mixed purpose room. Acoustical foam is also a great option for absorption in the mid to high frequency range and is very affordable. Foam bass traps are great for low frequency absorption and should be installed in corners to prevent standing waves which cause ‘warbling’. Diffusers come in many different shapes, all with the same basic purpose: to keep a room sounding ‘live’ by deflecting sound waves at many angles.