Measure the dimensions of the room and draw a quick sketch of the area. Include all corners, closets, doorways, windows, etc. Also add in furniture or estimate where the furniture will go if the room is empty.
Walk around the room with the boombox playing the genre of music that will likely be played in the area. If you are unsure or the area will host a variety of musical genres, pick a song with a lot of bass. Bass frequencies between 20 and 200 Hz are the most difficult to diffuse; if you make it possible for the room handle these frequencies, it will be able to handle any genre of music.
Play the music at a comfortable level as you walk around the room. Listen to the music closely, marking areas on your drawing where you hear an echo or the music does not sound as clear. These are the areas where you should place a sound diffuser. If you are building the room from scratch, calculate the optimal size for the studio using the complicated "Bonello Criteria." The Bonello Criteria is a set of conditions and calculations to predict a room's acoustical quality.
Select a sound diffuser to put in the areas where the sound quality was poor. Several types of sound diffusers exist depending on your needs. Some are made for the home; others are specifically designed for a recording studio or large concert hall. Diffusers are available in a variety of materials including wood, fabric, foam and metal. The most common type of diffuser is a fabric wrapped wall-mount panel, but there are also two-dimensional sculptural diffusers that come in almost every shape and size imaginable. Speak to a customer service employee at your local music store and show them your drawing for help in selecting the correct size and shape of diffuser.
Before placing the diffusers, isolate the room from outside sound or escaping sound as much as possible. Seal all doors and windows with rubber edging. Cover electrical outlets and use external hardware. Caulk around any other holes in the wall such as those around lights or wires.
Arrange the room according to the best possible sound quality. Set up the diffusers in the areas indicated by your original drawing. Mount wall diffusers securely with a drill and screws or the hardware provided with the diffuser; set floor diffusers on the ground following the directions carefully. The angle and exact location will affect the sound quality. Place a subwoofer in the corner of the room on a soft carpet to avoid extra vibrations on the floor, and then set up chairs and the remaining equipment. Keep the space as minimal as possible to avoid any other sound interaction.