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The Phantom of the Home Theater

Virtual speakers are no substitutes for ones that are properly placed and angled.

Let me run a scenario by you and see if it sounds familiar. You’ve just been presented with the architectural plans of the room where your client wants to put a home theater. You’re looking around it in a mild state of irritation and/or panic, thinking, “Now, where the heck am I supposed to put speakers?” There’s a door in the way of one, an archway where another should go, the room’s too short for wide channel speakers, too narrow for side speakers, there’s a refrigerator in the corner where you need to put a subwoofer, and the ceiling is a recreation of the Sistine Chapel so you can’t put top speakers behind, in, or hanging down from it.

Into the back of your mind creeps a thought that may be your salvation. Haven’t you heard somewhere recently that it doesn’t really matter where you put speakers these days? You can put them wherever you want, and there’s special processing that will make it all sound just the way it should? That may be the ticket…just the answer you need!

Narrative hat off; engineering hat on. Is this really the answer?

For the TL;DR crowd: Yes, you can use processing to move speakers around virtually and make sound appear to come from places it isn’t. Yes, it may solve some placement-related issues some of the time to the satisfaction of some clients. No, it is not a panacea, one-stop-shop that can be blanket-applied to any situation to satisfy every listener. No, it doesn’t absolve you of the responsibility to do the best you can to put speakers in the right place.

Let’s dig a little deeper.

Also by Anthony Grimani: Home Theater – It’s a Science, Not a Science Experiment!

The folks offering these virtual speaker-moving, re-mapping — whatever you want to call it — technologies are doing some really cool stuff! I highly encourage you to read up on it, understand it, and take full advantage of it. There are some very sophisticated calculations going on, and the mathematical models line up and make sense. I don’t want anyone to think I’m trying to take away from all that work. The opposite is true; I want to see more and better of these technologies move to the forefront, because, ultimately, they’re going to make it easier to get better sound. That’s a win for everyone in my book!

So what about that pesky part where it’s not a panacea? At the core of these technologies is the brilliantly simple concept of using phantom imaging to make sound appear to come from a point between two (or more) speakers rather than from any one of the speakers individually. That’s how you create a “virtual” speaker. Thus, it is reliant upon our ear/brain system’s ability to correctly interpret the aural cues and line up the sound where we want it. You could also say we’re “tricking” the brain, but that makes it seem somehow devious when it’s not.

As it happens, our ear/brain is really cooperative in this process when the aural cues come from certain directions — like in front of you covering an arc about 60–90 degrees. It’s also pretty effective directly behind you through about 30–60 degrees. The challenge is all the space in between — beside you and all around above your head. The ear/brain’s localization system gets substantially weaker and begins to fail us. How this all works is a fascinating subject, and if you’re interested in learning more about it, there’s a great BBC paper you should read from back in the 1990s. Really smart people have been thinking about this for a long time!

Also by Anthony Grimani: Keeping an Eye on Your Systems

What our modern technologies are attempting to do with advanced processing is help the ear/brain work better in the directions where it doesn’t naturally want to image sound. In some cases and in some rooms with some listeners, everything works together and a great result is achieved.  Unfortunately, there are conditions where, despite the best efforts of our best people, the spatial gap is simply too large to bridge with processing. It may sort-of work, be passable, better than no processing at all, but your client may still say, “Nope, sorry, my brain’s not buying it. This sounds weird.”

Our responsibility as designers and integrators is to get the best sonic results possible for our clients. The application in this situation is for us to not abandon the good fight to get speakers in the right places. Sure, there will be situations where that’s just not possible and you should be very grateful that there are technologies to bail us out! Clients still need to know that there are reasons we put speakers in certain places, at certain angles, and there are a range of consequences when we deviate from that. As long as everyone understands the stakes, it should be smooth sailing through a project regardless of whether the end result is achieved with all the speakers on spec or the wonderful magic of processing making us blissfully unaware that they aren’t!


Anthony Grimani (agrimani@pmiltd.com) is president of Grimani Systems, PMI Engineering, and Dimension4 Acoustics, with offices in San Francisco, Los Angeles, and Paris.

Chase Walton (cwalton@pmiltd.com) contributed to this article.

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