Part Two: Treating the Room
There’s lots of conflicting methodologies on where to place treatment, and how much to use. The consensus I’ve found is that treating most of your early reflection points with acoustic absorptive panels is good, but treating EVERY reflection is actually detrimental to your sound quality, as it can make the room sound dead and unnatural. Finding the right balance comes down to your taste, so it pays to start small and add treatment as you go.
There’s three kinds of sound treatments, although there are variations of each type.
Finding the right balance comes down to your taste, so it pays to start small and add treatment as you go.
First off, you have your typical mid-high frequency absorber. This is a 2x4ft panel of acoustic batting, mounted in a wood frame and wrapped in acoustically transparent fabric. These can be purchased places like GIK Acoustics but you can cut costs significantly going the DIY route. More info on that below.
One of my mid-high frequency absorption panel
These panels can be hung on the floor or ceiling, and are good for dampening an over-active room, and for strategically reducing the volume of early reflections.
Next, we have diffusion. In some instances, you might find after treating a room with absorption panels that you still have problematic reflections, but adding more panels makes the room sound too “dead.” Another option is to place diffusing objects against the wall, breaking up the sound wave by bouncing it in several directions at once.
You can purchase acoustic diffusion devices, but you’ll find that many household objects can be used to create diffusion. The classic example is a bookcase staked with a random assortment of books, but you can get creative. Again, how much diffusion comes down to taste. For a typical theater room, placing some bookshelves on the back wall is a natural way to incorporate diffusion while satisfying members of the household with an interest in aesthetics. Whatever you do, DON’T glue egg cartons together and think it will work as diffusion. https://www.acousticfields.com/the-egg-carton-acoustic-myth/
Finally, we have bass traps.
Bass sound waves are very long (At around 10hz, they’re over 100 ft). In typical home theater room sizes, this creates a number of unique acoustical problems. Massive bass waves crash back and forth, building intensity and sometimes cancelling one another out in various points in the room. The best way to improve bass quality is to put your subwoofer in the ideal position, or use two subwoofers to increase the number of optimal listening positions. However, even an ideally positioned sub (or subs) will require significant treatment to sound their best in a confined space.
The solution is bass traps, which are deep moderately dense absorbers which absorb the lengthy bass waves, turning their sound energy into heat. Unlike mid-range absorbers, it’s hard to overdo it with bass traps, so go wild. Bass energy tends to concentrate in the corners of the room, so they’re typically built as triangles that fit into the vertical and horizontal corners where the walls meet the ceiling and the floor. Like other treatments, there are both professionally built and DIY options available.
General Treatment Recommendations
While no two rooms are exactly alike acoustically, here are some guidelines to get you started with placing your treatment.
Virtually all rooms will benefit from treating the front left wall, front right wall, front ceiling and front floor, typically two or three feet in front of your speakers (the exact spot will vary based on the size of your room and your listening distance, hence the measurements). Your aim is to place panels exactly over the point where those earliest and loudest reflections are bouncing.
If you lack the time or cash to delve into treating your room, at least throw down a solid carpet.
Another rule of thumb is to avoid leaving large flat parallel surfaces untreated, as this will lead to slap echo (where high frequency sounds whip back and forth against the surfaces, unable to quickly dissipate). An easy recommendation for any room is to treat the floor! Thick carpet with a deep sound absorbing carpet pad will do wonders for any room. If you lack the time or cash to delve into treating your room, at least throw down a solid carpet.
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