Part 2: The Shape Of Things
In Part 1 of this series, I wrote about why I am turning part of my garage into a recording studio. This time is about going from that blank canvas of a garage and figuring out how many walls and doors I need and where they need to go. The answer is — more than you’d expect.
Starting with the basics this was my initial drawing of the garage with two cars in it. The building is 40'x30' and the right bay has plenty of room for cars, a motorcycle and some storage space. This is a huge step up from our Seattle garage which was not large enough to even fit a small car. Granted, that house was built in 1922 and they didn’t have big cars back then, heck they barely had cars. Once you take out the thickness of the walls, that leaves the left bay as about 550 square feet of opportunity.
When I think recording studio, my first thought is the traditional layout of a control room where the engineer and producer sit with all of the mixing and monitoring gear is and a live room where the musicians perform. Usually there’s a big glass window and/or door between the rooms. This layout works great in commercial studios where each person is playing their own role.
The next most common layout is a single room where both of these things take place. This is more common for a studio that is more focused on a specific aspect of recording, like just mixing or mastering. It’s also a popular layout for “project studios” where a smaller number of people will play multiple roles, like the performer who will also engineer and mix their own music. Generally, a project studio is “off-the-clock” meaning it is not billed hourly.
In my case, I also want to have room for my instruments and be able to play live and rehearse with people in this space. The project studio model works better for me. The “top” of the left side will be my mixing position and the bottom will be where we play live. Anything can be recorded from anywhere in the room and the only tricky part will be recording vocals or other instruments with microphones which need to be isolated from the sound coming from the studio monitor speakers. Before we solve that, though, we need to isolate the studio itself.
The Big Science of Room Shape
The dimensions of a room play a major role in how it will sound. The interaction of audio waves within a room is extraordinarily complex. Sound waves bounce off of every surface that isn’t specifically treated and different frequencies interact to either amplify or cancel themselves out depending on where they hit. Any given spot in a room could have one of these room modes where this amplification or cancellation is happening at some frequency. If your ears are in that spot, what you’ll be hearing will not be the same as what the sound source is. When mixing a song, that could mean that a song that sounds great in the studio, suddenly has way too much bass when you play it in the car.
Over the years, a lot of research has been done that has determined a set of ratios that are less likely to exhibit these room modes. Actually, there are a lot of different studies by the likes of Sepmeyer, Louden, Bolt, Dolby Labs and more on this. I put a bunch of these ratios into an Excel spreadsheet to try to figure out if any of them would work for me. The first think I learned is that my ceiling is lower than it would be ideally. Because of the way the roof trusses were originally built in the garage and the construction methods needed for isolation, it would be too expensive to raise the studio ceiling above 8.5 feet. Some research provided a ratio that will work well if the room dimensions are 24'10" x 18'3". As an added benefit, this gives me a bit of space for storage. Woo!
As I mentioned in the first article, sound isolation is a key for my studio because both the recording and the performing process can be loud enough to annoy neighbors and passing traffic or planes or barking dogs can ruin recordings. The best solution to this is known as “room within a room”. Basically within the garage we will create another room with walls and a ceiling INSIDE of the existing walls and ceilings of the garage. Then we add insulation and drywall in a very specific way to minimize the sound waves that can escape from the building. Finally, we seal the inner and outer rooms so they are airtight. If air can get out, so can sound. Windows are a notorious weak spot for sound (and air) to escape so we will need to cover up and insulate the windows on the left side.
Making a room within a room takes a lot of space. With multiple layers of drywall, the inner wall is about 6 inches thick and we need an air gap of at least a couple of inches between the inner wall and the insulated outer wall. Fortunately with 550 square feet we have enough to play with.
Adding a room within a room also means that we need to get in to that room which means doors. We’re removing the garage door on the left side since they take up a bunch of vertical space so we need one door to get into the garage on that side and then another one to get into the studio. From a safety perspective, we should have 2 ways of getting out of the studio in case there’s a fire. Since we’re covering the windows for sound isolation, we will need to have a total of 4 doors (two doubled doors at each entrance) to make it easy to get in and out of the studio while maintaining isolation. And those doors need to be very solid and sealed.
When all was said and done we came up with a layout that is as close as we could get given the research we did and the constraints that the garage gave us and it looks like this.
What you can’t see in this drawing is the ceilings. The studio ceiling will hang from the original trusses using resilient channel which helps to reduce the transfer of vibration from the ceiling drywall to the trusses themselves. This is important because those trusses are connected all the way up to the roof. Above those trusses, we’ll be building another ceiling which is mostly* isolated from those trusses. The lower ceiling will be 2 sheets of drywall and then insulation on top of it and then and air-gap. Above that will be more insulation and then 2 more sheets of drywall. Above that is a large air gap and then the roof of the garage which will need to have some ventilation in it so the goal is to stop as much sound in those first two ceilings because anything that gets past there has a clear path to neighbor-land.
Next up… measuring the noise
*mostly is not completely so we will likely have some vibration that gets out to the roof and that means we are not as isolated as we could be. This is a limitation of building into an existing structure and trying to keep the overall cost somewhat reasonable.