August 12, 2008
| by Dennis Burger
For the obsessive home theater aficionado, it’s the ultimate horror: you enter a friend’s house and spot a home theater system. Everything looks reasonably normal at first—left and right speakers flank the screen; a center channel sits above or below; but then you notice the rear speakers, stacked on top of the entertainment center at the front of the room. Or on top of the front left and right speakers. Or maybe one is at the side of the room and the other is in the back, each of them pointed in wildly different directions.
“Cleanup on Aisle Geek!”
When pressed, your host invariably gives the same sort of answer: “Well, I paid for them so I’m going to use them, but I can’t go running wires all the way around the edge of my room,” or, “I just don’t have room to put them back there,” or, “I really just don’t care.”
Catch your breath, count to ten, and remind yourself that “Surround Sound Speakers 101” isn’t a pre-requisite class in most college curricula. Given the amount of bad information on the web about surround sound speaker placement and even the importance of proper placement, it’s no surprise that the uninitiated are often confused. What’s more, there are so many different types of surround sound speakers—direct radiators, bipoles, dipoles… quadrupoles, for goodness’ sake!—it’s amazing that anyone other than professionals and diehard home theater aficionados end up with complete surround sound systems to begin with.
“If you can’t get a decent placement for your surround speakers, just don’t use them at all.” That’s the advice of Anson Fogel, co-owner and chief operating officer of the multiple CEDIA award-winning architectural electronics firm Electronic Systems Consultants (ESC) in Aspen. “If you can’t put them in a reasonable position—which isn’t that hard—just don’t install them, because otherwise they’re either not going to do much, or even make things worse.”
For a 5.1 surround sound setup, that reasonable placement for direct-radiating speakers—in other words, the typical forward-firing speakers that immediately comes to mind when someone says “speaker”—is slightly behind you, 110-degrees from the screen. If that number doesn’t make sense to you, think of it like this: Directly in front of you, toward the screen, is 0-degrees. Directly to your left and right—where many people think surround sound speakers should be placed—is 90-degrees. Keep on going another 20-degrees or so, to a point just slightly behind you, and you’re headed in the right direction for proper surround speaker placement. And if at all possible, try to keep them the same height as your front speakers, or perhaps just a bit higher if necessary.
Why is that the correct position? Fogel explains: “What you’re trying to do with surround speakers is to set up a soundfield that comes as close as possible to the soundfield that the mastering engineer used in the studio when he mastered the movie’s soundtrack. And his speakers are behind him, 110-degrees off of axis, because that’s what’s prescribed by the Audio Engineering Society. They’re not above him, they’re not below him, and they’re not right beside him. They’re not sitting on the wall above the couch with the couch shoved against the wall.”
Of course, the surround sound police aren’t going to come knocking on your door if you deviate from this. “Many times in residential spaces—normal living rooms, family rooms—strict adherence to these guidelines isn’t reasonable,” Fogel says. “You can certainly put them a little higher, on a bookshelf or something, and they can certainly come forward or move backward a little. But the closer you get to the ideal, the better your sound is going to be.”
These rules fly completely out the window when bipolar and dipolar surround sound speakers enter the picture, though. But before we start hanging them on the wall, let’s quickly discuss what the words “bipolar” and “dipolar” mean, and how such speakers work.
Bipole & Dipole
Bipolar speakers work in roughly the same way as direct radiating speakers. Instead of projecting sound straight ahead, though, they feature two sets of drivers pointed in different directions, which fire in-phase—both pushing and pulling air at the exact same time. “That gets sound moving toward more reflective spaces in the room, introducing more sonic energy in more directions, so that you get more reflected energy coming off of walls, ceilings, book cases, tables, et cetera, than you would with a direct-radiating speaker.” In other words, you’ve got more sound coming at you from more directions, but most of the sound is coming from the speaker itself.