Throughout the past 100 years or so there have been many different approaches developed for designing control rooms. Pretty much every approach has its followers. The way that I generally design control rooms incorporates elements from a number of traditional approaches. For more specific information on studio design principles and philosophies, there are a number of great websites and books such as the Master Handbook of Acoustics, Philip Newell’s Recording Studio Design, and Floyd Toole’s Sound Reproduction.
When compared to other approaches, I believe that what I like to do most closely resembles Northward Acoustics’s FTB designs but done to a lesser extreme since most people don’t have the luxury of losing so much floor space for treatment, having permanent construction alterations to the room, and of course, the cost.
I start by splitting rooms into 3 zones. The front which encompasses everything up to a little in front of the listening position, the listening position which is the area to the sides of and above the listening position, and the rear which is the rest of the room behind that. In general, I like to absorb all of the first reflections regardless of what zone they’re in. Using other techniques can lead to a wider sound but you trade off for precision in imaging. The front wall reflection point is a little less critical since you don’t get too much high frequency content travelling backwards from the speakers.
In the front zone, I like to have as much bass trapping as possible (using diaphragmatic absorbers as discussed in a previous post). The low end pressure has a tendency to build up around the speakers so I like to treat this as early as possible. This generally involves using large panels across the front corners as well as thick clouds.
In the listening position zone, I start to ease back on the low end absorption. In rooms with lower ceilings it can be helpful to use clouds here as well. This is the position where I’ll use more reflective and diffusive elements. This isn’t to interact with the speakers but rather for the comfort of the people in the room. This use of diffusion is very similar to that of Northward Acoustics. It helps with not feeling like your brain is getting sucked out of your head when you sit in the room either on your own or talking to other people. Of course some absorption in this zone can be beneficial depending on how it interacts with the room modes.
The rear zone is where I have the most freedom. The first thing which I always do is use a large bass trap on the back wall and potentially corners. This is where I generally put the thickest absorbers which the project will allow. In my own studio, I use a 12” thick panel along the back wall which has a number of different diaphragmatic materials inside. This also absorbs the rear wall first reflection point. I’m not a fan of placing diffusers there as again, while it can create a more pleasing sound, it takes away from the imaging.
The rest of the walls and ceiling of the rear zone I vary depending on the needs of the project. I’m very careful in this area to maintain an open sound as this is generally where clients will be hanging out and talking. I use a very careful balance of high frequency absorption, diffusion, and reflection which can always sit in front of diaphragmatic absorbers. This can also be used as a recording space. In my own studio, I’ve recorded a number of singers as well as guitar with excellent results. It’s a dry sound but very neutral and open. These parts of the room don’t react all that much with the speakers (other than the modal behavior) so I don’t worry too much about that.
In the studios I’ve designed, I use a variety of materials as mentioned in my diaphragmatic absorbers post. In terms of porous absorbers, I generally use Roxul Safe n’ Sound. I rarely use 703 as it normally does more harm that good. I’ve found that 703 is full of resonances and reflective behavior. There’s also the issue that you really shouldn’t use it beyond 4” thick. This has to do with the gas flow resistivity and acoustic impedance. In general, as your panels get thicker, less dense materials will provide better absorption. 703 is technically more effective in 2” panels than Roxul but it has the issues I previously mentioned so I find that Roxul ends up making rooms sound a lot better. Where I do use more rigid materials similar to 703 is in some small panels I like to use similar to those used by Golden Acoustics. I’ve found that using them in small pieces gets rid of the resonances.
One important thing to note with porous absorbers is where to place them when using them for low frequency absorbers. Contrary to popular belief, putting them in corners is the worst place to put them. Sound has both a pressure and velocity component to it which are inversely related. Yes, corners are where you get the pressure build up but porous absorbers work based on the velocity component. The reason that people put porous absorbers across the corners is that it’s the most convenient way to get the most distance away from the wall where porous absorbers get more effective. You can easily get a panel across a corner having a distance of over 12” away from the corner. Putting panels that are 12” away from the walls is generally not doable in most situations. By carefully studying the modal behavior of rooms, You can get more absorption with a panel on a wall away from the corner than a panel sitting across a corner. Despite this, I still normally put large panels across corners as it’s convenient for getting good distance away from the wall and provides a more broadband absorption.
When designing rooms, using a combination of measurements and listening is critical. Just going off of measurements likely won’t give you great results. After years of experimentation I can design rooms without necessarily having to listen by going off of my previous knowledge of what works and what doesn’t but many of the things I do either don’t make a difference in the measurements or actually make them worse but improve the listening experience. I generally use measurements to have a better idea of what problems I’m dealing with, how much treatment is necessary, and where to best place low frequency absorbers. Later on in projects I’ll continue to take measurements to see how well certain issues are responding to the treatment and to get a general idea of the final measurements in a room.
Unless one uses exorbitant amounts of treatment, a room will never be flat and it’s important to acknowledge that. Large peaks must be brought down and dips need to be filled in to the best of your ability. The most important factor is the decay time. No amount of EQ or DSP can deal with issues in the decay time. What EQ and DSP can deal with is flattening the rest of the room (within reason) after the treatment has done its job. I believe the EQ/DSP is critical in any studio regardless of the amount of treatment done to the room but of course high quality units and careful tuning needs to be done otherwise they’ll do more harm than good. In the box EQs can work well, Trinnov is a fairly good external unit, but IMO nothing beats the DEQX units. Even acoustic treatment can do more harm than good if not applied properly…
One thing I haven’t mentioned is the use of active acoustics. While I’ve done some research on low frequency absorption via active means, I haven’t applied it in any of the rooms I’ve designed. It can be very beneficial but I believe that traditional means need to also be employed in order to achieve great results. Where I have explored active acoustics more is in performance and recording spaces where they can be very useful. I may write a blog post about this but for anyone interested, you can find a paper I wrote on this on my Products page.