Speaker Placement: Bipole, Dipole & Direct

By Dennis Burger

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.



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.

“Bipolar surround speakers are so rare and esoteric these days that I don’t know why anyone is still talking about them, though,” Fogel says. “The real choice is between dipolar speakers and direct radiators.” Like bipolar speakers, dipoles feature two sets of drivers firing in different, often opposite, directions. Unlike bipolar speakers, the drivers in dipoles aren’t moving in and out at the same time, though. They’re not in-phase, that is to say. One driver pushes air while the other pulls. So when the dipoles are placed properly, at 90° from the screen, directly to the left and right of the listener, they create a null zone—an area in which the sound coming from each speaker effectively cancels itself out, kind of like matter and antimatter coming together, but with sound and with less earth-shattering kabooming. The sonic information coming straight toward your ears is effectively dampened, and instead you hear virtually nothing but sonic reflections. So instead of perceiving sounds as coming from the speaker itself, the result is a diffuse soundfield that seems to emanate from the room itself.

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[Link: electronichouse.com]

View slideshow of 25 Bipole/Dipole Speakers
[Link: electronichouse.com]