This three-part series takes a real world look at the why’s, where’s, when’s, and how’s of creating a professional-grade home recording studio. The articles were written as things happened, and include enlightening anecdotes, technical twists, and surprising turns as veteran producer/engineer Michael Tarsia attempts to actualize a vision that is shared by many recording enthusiasts.
The truth about isolation booths
Inner framing with Vib-X washer.
A ISO booth is a room within a room. The outside of the structure is of typical design, while the inner structure is meant to “float” separate from the outer structure (and the entire building) by means of insulators, like Vib-X pads and washers, as well as physical space.
The whole process of building the booth has been a bit nerve-racking for me. The room needs to float and be isolated, but air must flow through it. In addition, cables, wiring for lights, and electrical outlets must be strung through, and a door has to be installed. All of these holes in the structure can ruin the room’s isolation qualities if not treated properly.
Building the room
First the outer wall was constructed. At the same time, consideration for anything that had to be fed through the walls was mapped out and fabricated. This meant that all wiring and boxes had to be extended long enough to get through the two walls, and a provision for a run above the booth had to be put in to ensure ease of adding anything to the room at a later date.
Once the outer walls were finished, the Vib-X was installed on the footers and headers of the inner wall. The inner wall itself is situated so it doesn’t touch the outer wall of the booth. I found a 28-inch door and metal frame for an entrance and am now working on a design to place the door in an optimum position for both sound and space. A glass window is being ordered to give the ISO room door a view to the studio to make it less claustrophobic.
The inner walls, the ones you see as you stand in the finished room, consist of a layer of 1/2” sheetrock, Block Aid vinyl barrier, and 5/8” green rock.
The floor of the booth must also float off the room's original flooring. Wood blocks with Vibe-X “feet” and two-inch plywood with high-compression vinyl sandwiched in make the floating floor. Insulation will be packed in between the floating floor and the original flooring, and the edges of this floating floor will also be isolated from the inner walls of the booth.
Diligence in the construction process is very important. It can’t be stressed enough that the weakest link lowers the isolation properties of the entire booth.
I had hoped to have the booth completed by now, but that didn’t happen. Hopefully by next month, great pictures of a finished booth will be in the mix.
Wall treatments
After all the walls were sanded and primered, acoustic fabric was applied to all vertical surfaces. Sound Channels from Acoustics first is a dimensional fabric that combines excellent acoustic properties with a Class A fire/smoke retardant rating.
Sound Channels acoustic fabric covers the walls of the booth.
Sound Channels looks like carpet but is lightweight and easy to apply. At first we followed the installation instructions that said to “double cut” the material – that is lay the sections atop one another before slitting. This procedure is oftentimes used in putting up wallpaper, which is really what the process of installing Sound Channels is. But I think the instructions might have been for a different type of fabric. This had ridges, so we took a flat metal bar and cut along an indented furrow line of each section we fabricated.
Sound Channels adheres to the wall with Chapco 305, a specific adhesive that is made for interior wall carpet installation. This stuff is so good that we could skip the installation suggestion of putting temporary staples at the top of the fabric strips to hold them while the adhesive dries. Prepping is very important: sealing the drywall with primer before applying the adhesive paid itself back in dividends. This D.I.Y. job by an inexperienced installer took about 24 hours – I had to cut and adhere some 40 linear feet of the fabric. I should note that my room has many angles, uneven areas, and doors and windows to go around. Not to mention the booth has a bowed wall.
Half-round Geometrix sound absorbers.
Once the fabric was installed and cured, we hung the bass traps and absorbers that Nick at Acoustics First recommended based on a dimensional drawing of the space. On the front wall there are two half-round cylindrical broadband absorbers by Geometrix. These are made with 1-inch thick curved acoustical glass fiber with wooden supports.
Between the bass traps are two rectangular Sonora absorbers. On the ceiling over the engineering console there’s a Sonora panel made specifically to hang horizontally.
Floors and workstation
The next step was laying a floor for the studio. Half-inch plywood had already been glued and screwed into the floor. The next step was to lay flooring. I choose 3/4” Bruce hardwood oak. It’s durable, looks great, and fits nicely with the warm vibe I was looking for in the space. The oak was laid both in the control room and isolation booth. Trim was cut and painted for the floor and ceiling.
I ordered the VR 70 Argosy workstation with flat top rack sections for near field monitors. The console came neatly packed in about 13 boxes. It takes at least two people to assemble these babies, as some pieces are large and unwieldy, so my dad came over to lend a hand. It took us only three and a half hours of moderately-paced work to put the console together. The instructions were clear and concise and the fit and finish of the workstation was impeccable.
Okay… now the booth
I had to commit to cutting holes for airflow and wiring in the booth, and close the outer (visible) ceiling. I decided we should put a two-inch cant in the ceiling so it and the floor were not parallel. Just like the control room, the booth shouldn’t be dead, just controlled and pleasant. On the one large wall in the room, we took two pieces of leftover 1 1/4” round and mounted it vertically at the centerline of the wall. Then we took a piece of masonite (pegboard without holes) that was a little wider than the width of the wall. I am bad at math so we cut it with trial and error.
Once we found the right size to make a nice curve, centered at the now half-round “keel,” we screwed the masonite to the walls in two horizontal sections. Before the second section was in, we stuffed some fiberglass between the wall and masonite to hinder any sympathetic vibrations that sound waves might induce in the arced panel. We did the same thing for the top panel and then used duct tape to hold the two panels together before we put the Sound Channel fabric over it. Once all the fabric was installed in the booth, we put quarter-round up in the corners and top and bottom to further reinforce and hold the curve line.
Our next issue was getting wires from the workstation to the booth. I did not want to build a run through the floor, so I had decided early on to run plastic pipe up the wall, behind the console, then across the ceiling and into the sofit that was being used as a conduit for a room-to-room vertical fan.
After the pipe was painted and hung, we used a string that was set inside as a “fish” to pull six 22-gauge communications cables into the booth. Once inside the booth, we used Wiremold piping and Wiremold boxes to surface mount two boxes: one for microphone connections and one for headphones. We pulled three lines in each box. Two lines were connected to off-the-shelf switch plates with XLR connectors surface-mounted to them. The other line in each box was tucked in and is available for a future application. We made the same terminations on the other end of the wire and then connected them to my Digidesign 192 converter.
After the lines were checked, we mounted a room-to-room variable-speed fan to suck air out of the booth. This was mounted over the steps in the stairwell by attaching it to the sofit’s outside wall. Inside the sofit, we made two vertical half-inch-thick plywood plates and mounted them to segment the sofit into three equal zones. A large hole was cut in each. Now air being pulled out of the box had to run through three 90-degree bends, significantly lowering any noise that could seep through the opening.
Early on in the construction of the booth, we anticipated the need to have air flowing into the booth, but acoustically, you don’t want a straight hole through the walls. So we made eight-inch cuts in the outside wall, between two studs, and framed it with 2x4s. The same thing was done on the inside wall, offset from the other hole, so air and any sound it carried had to pass thru three 90 degree bends before it entered the room.
Final touches
This part of the work was the final major hurdle. The doors have been sealed temporarily with weather strip, and we’ll look at the door and the proper way to seal it on the next installment. Stay tuned next month for an honest evaluation and any changes that need to be implemented.
Michael Tarsia is a two time Grammy recognized Engineer, with 19 Gold and Platinum album credits. He is also a director and instructor for the Sigma Soundz Recording Arts Program. Learn more at www.myspace.com/miketarsia or call 215-837-1002.
