Broadband bass traps are available from a variety of specialty manufacturers like RealTraps, Primacoustic, and ATS Acoustics, and there are even some companies, like ReadyAcoustics that specialize in making affordable DIY kits. If you’re really handy, you can even build your own from scratch.
Step 3: Controlling Reflections
Once you’ve got your low end is in a workable place, many acousticians will recommend that you focus on high and mid-frequency absorption to create a “reflection-free zone” in the listening position of a control room.
The idea here is to use absorption panels that are just like the broadband absorbers already discussed, only thinner, as to lower the cost and gain more coverage.
Instead of going with rigid fiberglass panels up to 6” thick, you might opt for panels that are 2′ x 4′ or so and only 1” to 4” thick. 2” seems to be a pretty common choice, especially if you’ve already done a good job controlling low-frequency resonances.
The first goal is to eliminate first-order reflections – that is, sound waves from the speakers that bounce one off the walls, and then make a beeline straight for your ears. A small handful of strategically placed panels can help accomplish this quite well: one or two panels each on the walls adjacent to your listening position, on the ceiling above it, and behind the speakers themselves.
There are a couple of ways to figure out exactly where to place these absorbers. The ones you place on the side walls should be around ear level, naturally, and you might want to ask a friend to walk around with a mirror up against the wall. Any point along the wall where you can see the speakers in the mirror from the mix position is a potential place to put a panel.
Another way to figure this is to calculate a distance halfway between you and the speakers, and put absorbers there.
This is the first, and most essential step to controlling high and mid frequency reflections. If you want even more control, you can add additional panels from there, but even this alone can make the most reflective rooms into workable environments.
A similar approach can be taken in a live room. It’s never a bad idea to throw up some evenly spaced 2”-4” panels in a rectangular room, in addition to a few broadband absorbers.
If you continue to have problems with flutter echo, you can now add in 1” panels in problem areas to clean up any high-frequency slapback.
Step 4: Diffusion
Once you’ve treated your low end, created a largely reflection-free zone in your listening position, and cleaned up any significant flutter echo, you can think about adding diffusion.
Usually, diffusors are place on the back wall of a control room to scatter reflections, making the back wall practically “disappear.” All the companies mentioned earlier offer diffusion solutions, and some companies like RPG, Delta H Designs and Carl Tatz Design specialize in making custom, sometime breathtaking options.
But diffusion isn’t just for control rooms. A small live room can be made to sound larger, more open and less “boxy” thanks to a few well-placed diffusors. They can also be incorporated into a “live end/dead end” type of design, where one side of the live room is surrounded in thick absorption panels, and the other is accented by wood diffusors to help scatter the sound.
And once again, for the handy studio owners among us, there’s always the DIY route. All that takes is some wood, a good saw, a ruler, and plenty of patience.
Justin Colletti is a Brooklyn-based audio engineer, college professor, and journalist. He records and mixes all over NYC, masters at JLM, teaches at CUNY, is a regular contributor to SonicScoop, and edits the music blog Trust Me, I’m A Scientist.