RealTraps MondoTrap room acoustics treatment
So it's reassuring to now and then review a product whose mechanism of action is easy to understand. Yes, there are plenty of "room-treatment" products out there—little pieces of foil, small jars of colorful rocks—that no known laws of physics can explain. For that, you need psychology. But some less esoteric room treatments—represented in this review by the MondoTrap, made by Ethan Winer's RealTraps company—work according to well-established scientific principles. And I do mean work.
A little science
Science has two complementary foundations: the empirical and the theoretical. In order for something to count as science, it must be supported by rigorous, quantitative observations and—assuming it's not something new and paradigm-shifting, which happens far less often than tweak salesmen would have you believe—it must be consistent with existing theory. Let's start with the theory.
Sound waves emerging from a loudspeaker whiz by at more than a thousand feet per second. But when they bounce back and forth between parallel surfaces, they form standing waves, aka room modes: vibrational modes with points of maximum and minimum volume at fixed locations in a room.
Because the dimensions of most listening rooms correspond to the wavelengths of the lower audio frequencies (the wavelength is the speed of sound divided by the frequency), standing waves create the biggest problems in the bass frequencies. Play a recording of white noise—ie, equal energy at all frequencies—through your speakers, and the energy-vs-frequency response you measure in the room will be anything but equal, especially in the bass. To further complicate things, the room's response will depend on where you stand in it: one location will have too much midbass, but at another the midbass will vanish altogether—same for the low bass, but at different locations. Even if your audio system has a ruler-flat frequency response, the response of your untreated room will look more like the Himalayas. That's something even the most expensive preamp can't fix. An equalizer can help, but the results will sound good at only one location. But every room has walls, and walls reflect sound. What to do?
If you're building a dedicated listening room from scratch, plenty. For one thing, you can give the room the right shape: Make sure the walls aren't perfectly parallel, and that the room's height, width, and length aren't the same, or even simple multiples of each other (footnote 1). That'll spread out the standing waves over a wider range of frequencies and room locations. Another thing you can do, at least in principle, is to make the room big; room modes are less important in larger spaces because the modes are closely spaced (in the frequency domain). But big rooms have other problems, not the least of which is that they cost a lot to build. Besides, most of us are stuck with the space we're stuck with. What to do then?
If standing waves are created by sound bouncing back and forth between the parallel walls of a normal sort of room, the best way to control them is to stop the sound from bouncing by absorbing it. Certain materials—such as the rigid fiberglass that constitutes the core of the MondoTrap—are capable of absorbing sound energy and dissipating it as heat. The more energy you absorb at the room boundaries (footnote 2), the less is left to bounce off the walls and form standing waves. Those jagged response peaks and valleys smooth out; the room's response becomes more uniform; you get a taste, if only a small one, of what a genuinely flat frequency response would sound like, and the full potential of your high-end equipment begins to become apparent, probably for the first time.
Not Metropolitan Home
Until about 18 months ago, I had a dedicated listening room. It wasn't ideal—a little too reflective—but acoustically it was pretty good, and my wife and I could shut the door and listen at pretty high levels without disturbing my son, who (we hoped) was sleeping 50' or 60' away.
I gave up that listening room, along with the rest of our large house in the country (footnote 3), for a small condo in town on a park with an ocean view. My old listening room isn't that much smaller than this entire condominium, into which I've stuffed a dog, a wife, and a nine-year-old boy. Some would say I was crazy. Some have said it.
Footnote 1: Tom Norton's essays on designing an optimally proportioned listening room can be found here and here. In addition, a useful spreadsheet for calculating room modes can be found here.
Footnote 2: Actually, it doesn't matter where you absorb the sound, whether at the wall or in the middle of the room. But walls and corners are where the sound pressure is highest for all frequencies and room modes, so that's where traps are most effective.
Footnote 3: Technically, I haven't given it up yet. As of this writing, I still own it. But it's for sale, and I don't go there much.