RE/P Files: Control Room Design For The Small Studio

Construction Details

Once the room dimensions have been selected we can begin looking into the finishing of the walls, ceiling and floor.

Sound travels by both acoustic and mechanical means. That is, it not only travels through the air but also through solid objects. So, to minimize the leakage of sound between rooms we must provide both acoustic and mechanical isolation.

Maximum mechanical isolation is best achieved when the inner and outer walls are independent; as in the use of double-wall construction.

This type of construction uses separate, staggered studs for the inner and outer wall surfaces with fiberglass insulation in between (Figure 3).

Also, care should be taken to ensure that no holes exist between the two rooms, such as through adjacent electrical outlets or mic lines run through the walls, since an air-tight seal between the rooms is required for maximum isolation from air-borne sound.

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Walls other than those between the studio and control room may be of single-wall construction but should be packed with insulation.

As to wall surfaces, the heavier a wall covering is, the lower its’ resonant frequency. Normally we’ll want the resonant frequency to be as low as possible. Sheetrock will resonate at a lower frequency than thin paneling because of its increased weight. We can also reduce sound transmission and lower the resonant frequency of a wall by the use of a highly damped material such as sound attenuation board.

For example, by attaching thin wood paneling to sound attenuation board added weight and thus, damping will be achieved. This provides the twin advantages of an attractive surface that exhibits good acoustic characteristics. Typically, windows should be of double-pane construction with the two panes at angles to each other to eliminate internal resonances. All seals around the window should, of course, be air-tight (Figure 4).

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Experiments have led to the belief that the ceiling should be padded with 4″ thick fiberglass insulation folded slightly to produce a corrugated surface. This should then be covered with burlap or other similar material. The effect is to deaden the ceiling and reduce floor-to-ceiling resonances.

To retain a proper stereo image in the control room the need to have a room symmetric about its center (front to rear) axis has been well proven. That is, the side walls should be mirror images of each other. If they are not, the acoustic characteristics of the two walls may be different.

Let’s say one wall has a hard flat surface and the other wall is made very dead. The hard surfaced wall would produce lots of reflections back to the console making that side seem both bright and loud. The deadened wall would do just the opposite by absorbing the sound hitting it, resulting in a dull sound at reduced level. It’s obvious from this that the hard surfaced wall and the dead wall both have shortcomings.

We prefer to use side walls that are irregular in shape and texture to minimize resonances between the two walls and also to break up any reflections from the walls. We will try to avoid using deadening materials on the two walls because we do want them to retain a bright sound.

This type of sidewall construction can be seen in Figure 4, for which we’ve used cedar shingles to form a pattern on the wall. The wall also has a slight curvature to it to further reduce resonances between the two side walls. The surface formed by the shingles is acoustically hard but very irregular so that reflections produced by the wall are diffused. This will further enhance the stereo image produced by the monitors through decentralization of the sound source.

An additional prerequisite for proper design is that the console must be centered between the walls, and the monitors should be placed at equal distances from the side walls. The criteria for monitor placement has been outlined in Figure 5. From your position while mixing, the angle between the monitors shouldn’t exceed 900 and their axes should cross about one foot in front of you. If possible you should be about two-thirds of the distance back from the monitors to the rear wall.

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The choice of monitor loudspeakers is practically unlimited. The monitors ultimately selected should be as reliable as possible and be capable of high sound pressure levels. The reasoning behind this is that in mastering use a monitor is fed a fairly high continuous level of uncompressed sound. Allowing 10 dB of headroom for peaks in the music, a 95 dB SPL signal may reach 105 dB SPL on transients.

This is not very dramatic to the ear, but is a drastic change to the speaker. 10 dB translates to ten times power, so if we were using 20 watts continuous power for 95 dB SPL, the speakers would require 200 watts peak input for 105 dB SPL.