Home Studio Construction: A Case Study

Text: Brad Watts

STUDIO HOUSE PLANS

Brad Watts: Broadly speaking , Greg, can you describe to readers what the brief here was?

Greg Tailby: It was an unusual brief because this was a domestic house, so the ceiling height was a major issue. But knowing the type of isolation mounts we use, I knew we could fit the design into the domestic ceiling height as our isolation mounting methods take up such a small amount of space compared with any other mounting solutions we’ve come across.

BW: So what was the height you had to work within?

GT: Well, we were pretty much going for the maximum possible (starting off at 2400mm) and we managed to squeeze 2300mm out of the room. We managed to fit both the ceiling and a floating floor into approximately 100mm space – a pretty good effort I reckon. This was the major consideration, so once that was resolved and we realised it was possible, our next focus was keeping the isolation to an acceptable level. Because of the neighbours we really had to make sure we were keeping noise to the absolute minimum.

BW: And what did you manage to keep that down to?

GT: In our experience everybody says they want total isolation. But in reality you can work with a lot less than that. Here we really had to keep the entire structure completely isolated from the external house walls. This particular build has been very challenging in that regard because the neighbours are only metres away. We were aiming for a sound reduction level of around 50dB. To put that into perspective, it’s like not being able to hear somebody yelling their brains out in the studio when you’re outside the building. You shouldn’t be able to hear them at all. We’ve managed to achieve that degree of isolation.

BW: Obviously keeping the inner shell airtight was important?

GT: Absolutely, at the end of the day the brief was attempting to get as much isolation from a domestic structure while still keeping an acoustically useful amount of space in the recording area. With neighbours only four or five metres away and the exterior walls of the house consisting only of Gyprock and stud walls with a rendered cladding [external surfaces] we had to pay plenty of attention to the isolation and the sealing of the inner studio walls. Plus, there was a lot of glass to contend with. Glass doors and windows that all had to be double-glazed.

BW: So what did you have to work with?

GT: The original space was an L-shaped room, which lent itself to a couple of different areas. There was a bathroom coming off that room (which we converted to an amp room) but the rest of the construction is basically a room inside the main room.

We made sure that internal room didn’t use any parallel walls. Some designers aren’t concerned with splaying studio walls but I believe it’s the best way to avoid the effects of standing waves. It’s an odd shape inside but it helps to have all the surfaces splayed 7-8 degrees from parallel. So the angle between any opposite walls ended up being splayed approximately 15 degrees. Incorporating those angled internal walls certainly takes up more room, but it’s worth the space to avoid standing waves and low frequency resonances from right-angled corners in the room. This then avoids having to treat those problems by installing heaps of bass treatment. The interior shape probably took a couple of days of planning and design. Then it was down to deciding on the materials we had available. You can’t be too choosy when you’re relying on recycled building products and timber.

RECYCLED CONSTRUCTION

BW: I understand you relied on secondhand timber to keep the costs down. How did you go about sourcing it all?

GT: Well, the Trading Post is often pretty good but for this room we ended up doing really well out of eBay. There are people out there selling this stuff for a living – professional demolition firms. In one sale we came across a lot of 4×2 oregon, which was already aged and therefore structurally stable – the timber isn’t going to warp or move much more than it already has. In that case, the timber didn’t actually end up being cheaper than new, but it was well seasoned. Plus it’s nice knowing you’re recycling a resource. The guys that do the glass are very inexpensive though. They turned up on eBay and they pretty much supply the glass for free as you’re not technically allowed to sell recycled glass in this country. All they charge you for is cutting the glass and delivery. So for picking up large pieces of 10mm-thick laminated glass you really can’t go past it. We ended up with about $3000 worth of glass for 500 bucks delivered.

BW: So looking at the shots taken before construction you can see the typical Gyprock walls and the gap you’ve created in the ceiling.

GT: Yeah because the ceiling is also the floor for the rooms above, we took out the ceiling Gyprock and filled that cavity with 36kg/m³ Rockwool insulation. We actually tied the Rockwool using nylon string so it was dampening the floor above. So because those ceiling beams were about 160mm in depth it gave us some extra height within the cavity to play with. That extra space helped with bottom-end control by acting as a further bass trap and absorbing some of the lower frequencies. The new ceiling in the studio area was secondhand yellow-tongue flooring screwed directly onto the bearers. Again, that was about a third of the price of new flooring material. It was a little damaged in places but that didn’t really matter as we were double layering it and patched it with putty as we went.

BW: So looking at the wall construction, you’ve used what looks to be an unusual spacing for the studs and noggins.

GT: Yeah because we used the yellow-tongue flooring for the walls as well, we had to keep the centres at 450mm (the flooring material is 900mm wide). So when you’ve got two layers of flooring material you’re left with a very sturdy wall.

WALL DETAILS

BW: It was about this stage of the project where I saw you adjusting all the wall frames and positioning them using a number of small wood wedges. Why was this so important?

GT: Ah yes. Because all the walls are splayed at various angles, obviously the corners are all odd angles as well. The idea is to build normal stud and noggin walls, even though these walls have a lot more of both the studs and noggins. You then stand the walls up and place them into position so they aren’t warping or pulling on each other too much. Whatever shape the wall sections are I like to keep them like that and then fit cladding to that surface afterwards, rather than pulling the wall frames out of shape to suit the wall cladding. The other problem is that you can’t fix these interior walls to any of the house’s perimeter walls, as that will end up transferring sound to the exterior walls as well. So it’s best to get the interior studio walls sitting together happily. If there are sections pushing or pulling at other sections it all ends up buckling eventually. The 80-100mm wooden wedges are positioned to allow adjustment of each of the wall frames so they’re sitting together evenly. Once the walls are in position they can be fixed to each other, clad with yellow-tongue and you can then go around filling all the gaps with sealer so the entire inner surface ends up airtight.

BW: There’s a lot of work involved with sealing the outer windows as well. What’s required to keep these airtight?

GT: Well, the original windows in the outer wall are sealed with a further layer of 10mm laminated glass. Then the inside wall windows are a dual layer of 10mm laminated glass. Some people use different thicknesses because each panel will have differing resonances. With these windows we’ve over-engineered with the 10mm glass. You can actually get an STC [Sound Transmission Coefficient] rating of 50dB using only 5mm glass but because we had the 10mm glass we just went ahead with that. The fact that it was laminated also helped subdue any resonances via the glass. So what we end up with is the outside window double glazed, then the window on the inside wall comprised of two sheets of 10mm glass. It definitely creates the opportunity for sound to escape from that point but the thicker glass really keeps the STC rating up. Worth the trouble to give you access to some natural light.

BW: Once the walls are in position, what’s the next job to attack? Typically this is where Rockwool starts getting packed into the walls but I noticed you’ve used a different material.

GT: Yeah normally we’d start filling the wall cavities with Tontine or Rockwool. The outer side of the interior walls are covered in chicken wire. This allows us to lay the Tontine into position before the inner walls are sealed with the flooring material. Tontine is a polyester material that isn’t made from spun rock or glass fibre, so it’s safe to work with and much easier to install. We’ve used a generic brand where the 50mm sheeting we’ve used weighs about 48kg per cubic metre – it’s a great material for increasing the density of a construction. Cutting it can be a bit difficult so for this job we ended up buying a foam cutter as there was just so much to do. But if a $1000 foam cutter is a bit out of your league you can cut it reasonably easily with an electric kitchen knife.

THE TENSION MOUNTS

BW: Tell me about this ‘isolation mount’ system you’ve been using. During construction I saw these mounts used in various situations to separate sections of wall and, most notably, in the floor. Isn’t it basically the rubber hand-railing taken from escalators?

GT: Yeah. It works incredibly well as an isolation mount as it’s industrial grade rubber reinforced with three layers of canvas. Then the back part of it is all stainless steel bundled wire cable. Normally this stuff is about $700 per metre! But when it’s worn and stretched it becomes industrial waste so it’s an expensive piece of rubbish to get rid of. Once you find a shopping centre that’s happy to pass it on to you, they’re usually happy to give it to you for free. We cut it into short lengths and use it to replace neoprene mounts that would normally cost as much as 15 dollars.

BW: How did you use it to float the floor?

GT: We simply laid out the escalator handrail at 400mm centres – it’s a really cheap method of floating a floor. Instead of building a complex timber subframe, which is expensive and takes up precious height, we simply laid the handrail straight onto the concrete slab. The gaps are then filled in with polyester and the flooring is put straight on top. The flooring has to be a ‘scribe’ fit (very accurate cuts that follow the contours of the wall – a time consuming job) with a neoprene seal between the floor and the wall. Then because the floor isn’t attached to the walls at all, it physically floats so you’ve got to have a little bit of play in it.

BW: So can you explain to me what the isolation mounts do?

GT: They isolate one large structural section from the next. The interior walls, floor and ceiling are all separated from the external walls, floor and ceiling with these mounts. The sound energy loses transmission via a mount like this. The idea is to have the entire interior shell floating on rubber.

BW: You’ve also opted for an unusual approach to the doors. Tell me about that.

GT: Yeah, I haven’t built doors this way before so I’m keen to see how they work out, but so far they appear to do the job. Apparently this is how the BBC specifies its studio doors. It’s about 75% of the price of a normal solid studio door we’d build, which would be two solid-core doors sandwiching high-density fibreglass board in between. Again, that’s fibreglass so it’s not the greatest material to work with. These doors are built with a 70mm surround section filled with polyester, then there’s perforated board inlayed all around the door’s edge. The idea is that any sound trying to escape via the gap around the door will be absorbed and not make it through to the adjoining room.

After the doors are hung in position, the middle section is filled with dry sand. The door itself is a good 120mm thick by the time it’s all done. They weigh a lot, so it’s best to fill the centre section with sand after hanging them.

So far it’s working well and it avoids relying on seals around the doors being the only form of sound reduction. Seals inevitably become less and less effective as time goes by, and doorways always cop a thrashing when you’re constantly moving equipment through them. So it’s a good idea to make all your doors wider than a domestic doorway. There are simple rubberised seals at the bottom of the doors and around the door-jams but the perforated edges absorb the majority of the sound. Once the doors are installed there’s each of the penetration points to consider.

BW: What exactly is a penetration point… dare I ask?

GT: Power and tie lines need to get in and out of the room. These points can compromise the complete isolation of the room. You can’t completely seal around a stack of cables so we build a set of staggered baffles around the point where the cabling enters the room. They’re basically boxes within boxes and the cables enter and leave the baffles at alternate sides of the boxes. The boxes are also filled with polyester insulation so any sound attempting to get out through these points is absorbed on its way through the baffles.

So there are two skins on the inside wall – both are different materials, again to absorb resonances. From the inside out there’s an 18mm MDF sheet, then the yellow-tongue flooring. The very inner MDF ‘skin’ – the final interior of the room – is sealed completely with mastic. Any holes, cracks or gaps are completely filled. Mastic is itself very dense and makes a good seal on the inner MDF membrane but it’s a good idea to go completely overboard on that and make sure you’ve pushed plenty of it into all your corners and joins to make a sealed room. We paid a lot of attention to getting as much mastic into the joins as possible.

WALL FINISHES

The final finish on the walls is a cotton-based upholstery fabric that we stapled to the walls. The edge sections and joins are all covered in a thin plywood strip that we covered in the same fabric. Rather than breaking up the finish with a visible line, we spent the time setting up these covers – otherwise anything visible would have made the ceiling feel much lower.

CEILING FINISHES

BW: So tell me about the ceiling finish. It looks fantastic but must have taken ages to do.

GT: Not really, maybe a day or so. I’d acquired an amount of recycled cedar weatherboard that had already oxidised in the outdoors and had done all its settling and shrinking. The cedar has a lovely feel about it and I really wanted to use it for this project in some way. Julian also loved the look of it but the boarding wasn’t quite angled enough to diffuse properly. So I ended up actually cutting the cedar edgeways to get a 15° angle from it – I just cut it to size then ripped it down the middle at an angle with a band-saw. You end up with two wooden tiles out of each section, so it doesn’t use that much timber. Putting it up just requires a bit of patience and some Liquid Nails contact adhesive. By the end, we had enough to do both the studio and the control room.

CLEAN POWER

Clean power is a prerequisite when you’re driving thousands of dollars worth of audio equipment. It helps with the longevity of the gear and avoids ground hums, earth loops and associated buzzes and interference. Julian spared no expense when fitting the studio with a power system that ensured reliable and clean electricity.

Julian Swain: Essentially, there’s a battery charger running continually from the mains, which is hooked up to four 6V batteries. The charger provides 24V DC to an inverter that, in turn, inverts that battery power back into 240V AC. The entire house is powered by a three-phase system where one phase runs the house and everything upstairs, another phase drives the air conditioning and the third phase powers the battery charger and all the lighting in the studio. So everything in the control room and the studio gets a constant, clean supply of 240V AC power.

If needs be, we can also switch back to the direct power in the studio and bypass the inverter system – just in case the situation arises where the studio is drawing too much from the inverter system. It could happen if I had a wall of Marshalls in there, but I dare say it’d be an extremely rare occurrence. All the electrics in the studio and control room are star earthed, therefore the inverter has its own earth spike, separated from the main house earth spike.

BW: So hum issues were the main concern for the inverter system?

JS: Yeah primarily, but nice clean power makes a noticeable difference to the gear’s performance, plus it isolates you from any interference from domestic appliances like the washing machines or light dimmers. It also offers a good degree of surge protection. Any minor surges get absorbed by the batteries and never make it to any of the equipment. The inverter is made by an Australian firm called Selectronics – their inverters give pure sine wave power.

The charger is made by a Dutch company and is actually a marine boating product. Because the unit is set underneath a section of the house, but is still exposed to outdoor temperatures, I figured it was better to go for the heavy-duty marine model.

THE BITS THAT MAKE IT GO

With the initial spec’ing of the studio’s equipment we were faced with a relatively small area for the control room. A large console was out of the question so the concept was to do away with the console and mix ‘in the box’ along with outboard processing and compressors. A Mackie control surface is brought into use when required, but for the majority of the time it’s hidden away. Monitoring is via the Presonus Central Station and ATC SCM 20-2 actives.

Trying to cover as many bases as possible made a pair of ‘British Mod’ Distressors an immediate choice for dynamics, along with the two dbx 160s, the valve compressor in the TL Audio C1, an API 2500, Manley VoxBox and the rather quirky Oram Sonics. The budget did have to end at some point so LA-2As were left out of the equation – for the moment the Universal Audio UAD LA-2A will have to do.

Microphone preamps are a mixture of valve and solid state with a number of classics such as the VoxBox and V76 clone by Mercury Audio. The API 3124+ is also a gorgeous set of pre’s for drums and guitars. All of the TL Audio preamps have had valves replaced with NOS (new old stock) Telefunken valves, which improve their sound immeasurably. They’re not exactly ‘go to’ preamps but the C1 is a very clean and reliable stereo pre.

During the wiring, everything was connected to Behringer patchbays using Klotz cable and Amphenol connectors. It was during the initial wiring of the gear that I decided it was imperative to keep the G5 Macintosh and hard drives relegated to a machine room situated under the stairwell. So computer noise is gone!

UP & RUNNING

So at the end of the project (do these projects ever really end?) Julian has a control room and studio that leaves him completely self reliant for the audio projects he takes on. Sound leaking outside has been brought down to acceptable levels and the sound inside the room is just terrific. In the brief time the room has been up and running I’ve had the chance to work on a couple of sessions in the room and have been very pleased with the results. Outside the house you can only just hear a kit being played. And the huge Mesa Boogie head and quad-box, which have found themselves a home in the isolation room, are hardly audible outside. The crazy thing is, the people next door responsible for most of the noise complaints, sold up and moved the week the room was finished!