Taming the Booth

The iso booth is a small room (about 6ft. square) which left untreated presents a number of sonic issues. Firstly, and most noticeable, is a flutter echo from the parallel wall surfaces which persists in the upper midrange for around 100-150ms (rough guess). Placing 3ft. x 3ft. wall panels containing 2" thick wedge foam squares in a staggered orientation on three of the walls took care of the flutter.

However, as can bee seen below in Fig. 2, the second problem then became even more apparent – a resonant node around 200hz. In numerous experiments we found that by placing thick foam cushions into the corners the problem was largely eliminated.

After some research it appeared the Auralex LENRDs and 12" cornerfill cubes would be an easy-to-install, and visually attractive solution. The combination package of 4 cubes and 12 LENRDs (the ATOM-12 kit) is reasonably affordable. As you can see from Fig. 3, a 12-15db reduction at 200hz was achieved, and the nasty node was put to bed.

ABOUT THE TEST: The goal was to get a basic idea of what was actually happening with the addition of the various sonic treatments, and to determine just how effective they were in frequency absorption. One of the Mackie HR824 reference monitors was placed in the center of the booth, about 3 ft. off the floor, and facing the back wall. The mic, also facing the back wall, was placed about 12" above and directly over the monitor. An omnidirectional pattern was chosen with the intent of obtaining a less localized sampling of the frequency response of the room than of that with a cardioid pattern. (The omni pattern and the mic's position in the center of the room may explain the cancellation effects around 100hz shown in the graphs.) Then broad spectrum noise was broadcast through the Mackies at consistent levels for each of the stages of room treatment.

While this test is admittedly flawed from a purely scientific stance, and was conducted under conditions that would surely give a Dolby Labs tech nightmares, it still provides a basic indication of the sound absorption capabilities of the Auralex product in a real-world, unbiased environment.

Redressing the Room • Managing the Cables • Workspace Upgrades • Taming the Iso Booth

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