Respecting Room Dynamics Juneau AK

Um, what's diffusion, and why do I need it?" the client asks. Slowly, I take a breath, count to 10, and consider my options. First, I could scream, stomp around the room, and pull out my hair. Second, I could suddenly remember that I'm terribly late for another meeting (which is probably true) and beg to be excused. Third, I could remain calmly in my seat, smile, and politely explain the answer. Considering the nature of this client and his job, I chose option number three.

Here's the sad thing. You might think that this client is a novice end user-the type whose digital clocks all blink 12:00. But he or she could just as easily be a custom integrator. I see it all the time: People who design home theaters for a living who don't know what diffusion is or why they need it. What's particularly frustrating is that I have spent many hours over that past two decades doing my best to educate them.

So let's make this real. Do you know why diffusion is important in home theaters?

Small Room Acoustics 101
I'm going to assume you know a little about room acoustics. After sound leaves the speakers, some of it goes directly to your ears, and a lot of it reflects off the walls before going to your ears. It is this reflected sound that can cause problems if it's not tamed.

I'm also going to assume that you know about absorption-that it's an effective way to treat problematic reflections. You put an absorber on the wall where a strong reflection occurs, as in the case where a speaker or listener is really close to the wall. Hopefully, you know, too, that acoustically treating a room is not as simple as putting absorption everywhere.

Every room has a specific balance of direct to reflected sound that will make the room feel natural to listeners. You need some absorption, yes, but also some reflections. Typically, you should only cover about 25 percent of wall surfaces with absorption. Exceed that amount and the room will start to sound too dead. Seventy-five percent of the wall surfaces will still be hard and reflective, leading to reflections that could cause errors in sound clarity. You can simply break up these reflections with diffusers (Figure 3). They generate uncorrelated and random acoustic energy that sounds more like the pleasant reverberation of a concert hall and less like the annoying hard reflections you often hear in small rooms.

The right balance of absorption, reflection, and diffusion will create a more pleasing sound field with better envelopment, better imaging, and a wider sweet spot.

All Things Wild and Scary
If you have your thinking cap on, you may have realized why diffusers are very often weird and bizarre shapes. Their purpose is to create as many uncorrelated reflections as possible. The most efficient way to accomplish this is a "panel" with wildly undulating surfaces. Believe it or not, there are actually many different kinds of diffusers, officially categorized according to the scientific way in which they scatter s...

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