How To Build A Pro Control Room (Part 1: Isolation)

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We can't all build professional control rooms, but we can learn a thing or two from how they are built and hopefully apply it to our own control room design. This will be a multi-part series in which I go through a control room design by world renowned studio designer, Philip Newell. 

1) Site Selection

Professionals would never build a studio in an unsuitable location for recording. In this design the building was already inside a concrete shell. The concrete floor ceiling and block masonry walls were an excellent starting point for a high level studio.

The space was also massive. The control room had 7m x 7m of floor space to work with and 8m of height! That is roughly 23' x 23' and 26' tall ceilings. That is unheard of in the home studio word. Ironically, over 50% of that space would be used for isolation and acoustic control of the room. 

2) Isolation Walls

The first step in designing the professional control room is to design the isolation walls. Newel used a concrete block or cinder block filled with sand for his interior isolation wall. In his design he angled the walls slightly, but he states in his book, Recording Studio Design, that both angled isolation walls and room ratios are not of much importance because they will not greatly fix low frequency modal issues. However, angled walls in the acoustic wall can be helpful for the reduction of flutter echo. 

The isolation walls are built with a 5cm-10cm gap from the exterior walls of the building. That is roughly 2-4" of space between the walls. I don't think he added insulation between the walls, but this would help with some added isolation, however the extra cost and labor would probably not add a noticeable difference in the isolation of this structure. 

Lastly, the isolation walls for this design were 4.5 meters tall or roughly 14.7 feet. Remember, when the studio is finished much of that height will be lost to acoustic control. 

3) Isolated Concrete Slab Floor

Because this mix room is not the main floor of the building and it will share a foundational floor with a tracking room, Newell is using a floated concrete slab. For home studio, I usually urge people not to float floors due to cost and expertise, but again this is a professional studio with millions of dollars in investment and profits at stake. 

The first layer of the floor is a 10cm 70kg/m3 (4" 4lb/ft3) layer of mineral wool. This is the spring that will isolate the concrete slab. You can use isolation springs, but they are more costly and difficult to use. I believe Newell felt the isolation would be adequate for this design. He also states that this method could lead to better isolation because of the damping of the structural floor beneath the mineral wool. 

After the mineral wool you need to add a layer of plastic to prevent the concrete from soaking into the mineral wool. After that he added two layers of overlapping OSB took prevent the mineral wool from getting trampled by the workers laying the slab. 

Lastly, they poured a 10cm concrete slab (4") over top of the OSB sheathing. 

To keep the concrete from touching the isolation walls they added a vertical layer of mineral wool between the isolation floor and the isolation walls. This ensures that concrete never reaches and connects the interior walls with the interior floor. 

4) Ceiling Joists (Isolation Ceiling)

Now the exterior ceiling of this room is at 8m and is a concrete ceiling. The second wall to complete the isolation shell is made of huge reinforced wood beams. The beams are made of two 20cmx5cm (2x8) boards glued and nailed together. Then a 10cm x 5cm (2x4) added on the top and bottom and finally two 25mm (1/2") plywood sheets glued and nailed to each side. See the diagram below. 

I put these beams at 16" OC, but for construction of this nature it would be wise to have a structural engineer on your team to verify loads and make sure you are not over sizing or undersizing your beams. 

Below is another image of the finished beams attached to the inner isolation wall. You may be wondering if this short circuits isolation. I wondered the same thing. My thinking is that Newell knows the acoustic shell will be also helping with isolation and the need to decoupe the ceiling a second time is probably not necessary. Plus, the isolation cap, as he calls it, is far below the true ceiling of the room. This will also help with isolation. 

Now I am not going over how the isolation ceiling is finished, because that will happen last after the acoustic shell ceiling is finished. We will go over this next week in part 2 of this series. 

Conclusion

Home studio soundproofing and pro studio soundproofing may look very different. If someone gave me a big enough budget I would use Newell's design, but for most of us mere mortals we must use the best materials we can within our budgets and space constraints. 

This said, using concrete sand filled blocks and choosing a suitable location for your control room will always put you in some of the top designed studio in the world, at least in terms of what you are starting with. 

My hope is that this helps you learn more about how the pros design studios so you can glean some wisdom from this approach. 

Works Cited - 

Philip Richard Newell. Recording Studio Design. New York ; London, Routledge, Taylor & Francis Group, 2017.

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