Your Room Acoustics.
The physics of sound propagation is complicated. When you’ve got a sound system in a room, your experience does not only depend on your gear but also on the propagation of the waves in the room. The walls, floor, ceiling, furniture.. All of these things play an important role in how the emitted sound reaches you and in what quality. It is very difficult to predict what will happen to the sound waves once they’ve left their source. And this arbitrary movement is unique to each room. It doesn’t take a lot to say that two congruent rooms which have concrete and plaster walls, respectively, sound very different.
“But I’ve got great speakers…”, The Purpose of Acoustic Treatment
A room without a proper acoustic treatment has an uneven frequency response. You can buy the highest grade speakers, but if you put them in an untreated environment, your room is host to a lot of acoustic distortions. These distortions twist the sound you’re trying to hear. This colouration and overlapping blankets the true, original sound. These distortions are the invisible foe you face when you put any sound system in a room.
Before identifying the problems, the first thing to think about is what outcome you desire from an acoustic treatment. The ultimate aim is to restore a neutral sound balance. Acoustic treatment means interfering with the path of sound to control the energy and thus, improve the sound quality.
- Killing the Early Reflection: If you’re tight on money and can apply just one treatment to your room, and you want it to be the most effective treatment? Do what, put some acoustic panels on your first reflection spot. This will create a sweet spot for your listening position. Ideally, you would create a reflection free zone around the listening position. If you don’t treat these, the early reflections will interfere with the direct sound from your speakers to cause comb filtering. This acoustic distortion causes colouration, masks details and prevents accurate localization. A tiny amount of filtering sounds musical as it, naturally, is a part of reverberation. Harsh filtering, however, is just bad and the biggest obstacle in the road to sonic clarity. Kill the comb filter.
- The Low End Beast: The monster of the low end frequencies haunts all small, untreated rooms. The monster is the total accumulation of mayhem at low frequencies. The main sources of this include room modes, the speaker-boundary effect and other acoustic distortion which results from the low frequency waves trying to exist in small rooms. Room modes are the natural resonances resulting from the room geometry. These resonances mask some tones and emphasise others. Certain frequencies decay slower than others, causing the phenomenon of the “one note bass”. The speaker boundary effect is caused when the reflected wave interferes horridly with the source. This speaker boundary interference response causes deep dips in the bass response. Your speaker placement and “trapping” the base, ie, bass absorption are the surest ways of ridding yourself of the problem. The ideal places to place “bass traps” are the room corners. The “bass traps” help in preventing the omni-directional bass waves to group and create bass heavy spots. Heavier, wall mounted traps can cut through the room modes.
- Diffusion: Sound diffusers treat sound without absorbing them. It is similar to reflection, but instead of all the sound being reflected at once, it is diffused and reflected to your ears at different intervals. This means that placing them will retain some life in your room. Diffusers also bring about a musical, airy feel to the sound. Recording studios use thick bass absorption on the rear wall, but many use diffusers on the top to scatter high frequencies. This brings about a sense of spaciousness.
- Reverberation Time and the Liveliness of the Room: The liveliness of the room is measured by the reverberation time (RT60). RT60 is the measure of the time it takes for the sound pressure level to decay by 60 dB. Small rooms don’t have true reverberation even. A small room has a decay time between 0.1 and 0.3 seconds. A control room or a listening room ranges between 0.2 and 0.5 seconds. Classical music dictates something between 0.4 and 0.5 seconds and if you’re listening to rock ,the range should be between 0.2 and 0.3 seconds.
- Decoupling and Isolation: While you’re thinking about cutting all the interference, it is good to start at the source. Decouple your speakers and subwoofers from your desk or floor by placing a dense platform under them. This will prevent the furniture to resonate with the speakers. It will also cut the bass which would travel through the walls and the floor to other rooms.
- The position: Ideally, you’re trying to create a reflection free zone around the listening position. The reflection free zone means that you listen the sound directly from the speakers, instead of interfering here and there. Don’t sit yourself too close to the walls, or keep any of the speakers near. Seat yourself along the longer part of the room, this lets the lower frequencies develop.
The sound in an acoustically treated room takes on an entirely different dimension. It is more magical and crisp. An untreated room will have your ears crying out loud, wishing for something better. But if you treat your room right, your media will shine.
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