While no control room is acoustically perfect, professional recording studios must create the flattest response and the largest sweet-spot possible. Acoustics need to be part of any control room plan and it is most successful during the planning and construction of the room itself. Building a control room in this way, reduces the need for lots of "add-on" or surface mounted acoustic treatments. Additionally, most treatment products in the market today simply do not have the acoustical performance of built-in and well designed treatments.
While we try to build the most acoustically flat response into the room, there are many other factors which limit the actual result. First of all, proper room treatments, especially in the low frequencies requires a lot of space. It's a simple matter of physics. Since the speed of sound and the wavelength of a frequency is constant, proper trapping, diffusion and tonal control of the low-end is extremely difficult and expensive. For example, the wavelength of 30Hz is a staggering 37 ft long.
Other factors in control room acoustics include not only the demensions, but the proportions. A basic rule of thumb is you want a room which is longer (from mix position to rear) than it is wide. We also try and stay away from demensions divisible by 2. One last cardinal sin is make a room a cube like 10' x 10' x 10'. The demensions of any space without angled or splayed walls dictate the room's nodes. Room modes are the collection of resonances that exist in a room when the room is excited by an acoustic source such as a loudspeaker and every room has them. In an untreated interior drywall room, typical of conventional construction, these nodes pose acoustical issues throughout the frequency spectrum, and thus your final mix product.
Room nodes, frequency response, and room resonances are only part of what we need to acoustically control. Even if the rooms response is relatively flat, you still need to control decay times and RT60 values. If a room has a nice flat low end from 60 to 100Hz, it will still sound boomy if those frequencies take 600ms to fully decay. Properly controlling decay times is just as important as frequency response, and is, many times completely overlooked.
When a room is not as flat as it can be and decay times are not under control, mixing in it can be a real challange. The main reason for this is that what you are hearing, and ultimately printing to your final mix pass is not reality. You shape you kicks, bass, guitars and vocals to what you are hearing, only to have the room's inaccuracies color your mix decisions. The mix may sound great in that room, but the minute you listen in another environment, the mix is off.
The more accurate the room you record and ultimately mix in, the more glued your mixes will be. The result will be a more focused, more clarity and balanced product.
I'm busy working on my blog posts. Watch this space!