Many electronics manufacturers try to make consumers believe that high cost electronics will guaranteed great picture and sound. Unless you have considered the room that you are using during your design, you could end up very disappointed with even the very best systems or electronic packages available. The fact is that the home theater system cannot be separated from its room. Hardwood floors, large windows, drywall and furniture do affect the sound quality of your system.
The good thing is that with proper home theater design these pitfalls can be avoided. Nobody wants to build a home theater that they cannot enjoy at above average listening levels, everyone wants that thundering bass. Also nobody wants their spouse, kids, parents or neighbors complaining every time they sit down to watch a movie that it is too loud in adjoining rooms.
In December we started a breakdown of Home Theater Acoustics, how they pertain to the room, and covered how to tame reflective sound. The two main ways to control reflected sound are by absorbing or by diffusing (scattering) these reflections. The first article covered sound absorption and touched briefly on diffusion. In this installment of Home Theater Acoustics 101, we would like to explain diffusion in more depth and why it is important in creating a home theater that really blows you away.
Sound diffusion is a technique designed to scatter sound waves. The idea here is to take the sound waves that are coming at your first point of reflection and break them up, or scatter them, into smaller components and equally disperse them throughout the room. Sound diffusion can take many forms, depending on the desired look and feel of the room. It’s important to note that diffusers have a specific task in the theater and should not be used in critical areas such as first reflection points as they provide little sound absorption.
Remember, we don’t want to absorb or diffuse all reflective sound. Without any reflective sound, your system loses the “spaciousness” and will make your home theater sound as if you are stuffed in a box full of cotton. What we really want to do here is take the reflected sound transmission and tweak them. In order to do that, the first thing that must be determined is the first point of reflection from your speakers.
In a nutshell, first reflection is the point on the sidewalls, ceiling, front wall (wall behind speakers) and rear wall of your listening space where the sound waves from the speakers will make their first reflections off a hard, reflective surface before they reach your ears.
Why is that important? Well, these reflections reach your ears after the direct sound wave from the speakers. Now, we’re only talking a fraction of a second but that’s enough to set up echos that will detract from your system’s ability to image to its full potential and deliver the sort of fidelity it’s actually capable of delivering. You don’t actually hear it as an echo the way you hear an echo in a big auditorium, canyon, tunnel, etc., but it’s enough to play havoc with your speaker’s sonic capabilities. And the sound waves don’t stop once they reach you. No way man! Like that tiny, super bouncy ball we all loved as kids, they continue bouncing around the room off of any hard, reflective surface they come in contact with. This is why a room with hardwood floors and bare walls will actually have audible echos compared to a carpeted room with drapes/curtains. Even if you have carpeting, drapes or plushy, covered furniture and the echos are not as audible, you still don’t have near the sort of control over the reflections/echoes that having absorption panels on the walls will give you. While some of this bouncing is good and makes the audio sound natural, too much is bad. The key here is balance. You want some bouncing, or reverberate sound, but not too much.
Once the first point of reflection has been treated, it’s time to start diffusing the space. As mentioned before, diffusion takes the sound waves, breaks them up and scatters them throughout the space. This has two effects; the first is that a strong first reflection is reduced and the second is that the energy is redirected so that it remains in the room but the sound arrives later and at a lower level, having traveled a longer path. A further benefit is that a small room actually sounds bigger when treated with diffusion, while a room treated only with absorption tends to sound more controlled until it becomes dead.
Diffusion panels are best used to treat problem reflections in the rear of the room, such as the back wall or rear side walls. You’ll avoid excess deadness in the rear of the room and create a nice, enveloping sound field. Diffusers improve the surround field creating a more immersive experience for the listener. In their natural state, diffusers give an appearance befitting a recording studio rather than a home theater. For this reason they are generally hidden behind an acoustically transparent fabric.
Sound diffusers are going to multifaceted squares or rectangles and are commonly available in fabric finishes, wood finishes, and paintable finishes. Our sales and design team can work with your builder or interior designer to add elegance to your space while still providing superior sound performance. If you are interested in learning more about acoustic treatments for your home theater, give us a call and we’ll schedule a free consultation and walk through.