Understanding the Different Pole Positions of Speakers
Although you'll most often find two-way (woofer and tweeter) and three-way (woofer, tweeter, and midrange driver) speakers on the market, you'll also run into speakers with more than one set of speaker drivers, facing in different directions:
- Monopole: These speakers have all the drivers on one face of the enclosure. These can be used anywhere in your home theater. These are also called direct radiating speakers.
- Bipole: These speakers have drivers on two faces, opposite each other. These are designed for the side/rear surround speaker applications.
- Dipole: These speakers have drivers on two faces, opposite each other. These are designed for the side/rear surround speaker applications.
- Omnipole: These speakers radiate their sound in all directions, in a 360-degree fashion, and are popular for outdoor applications.
There is a distinction between bipole and dipole speakers. Harken back to your science class days when you studied topics of phase, specifically being in phase and out of phase. If you recall, in a general sense, something is in phase when it acts in the same pattern and time session as something else, and out of phase when it doesn't. Because controlling the way sound waves interact with each other is a key component of home theater, you have to deal with the concept of phase.
Bipole and dipole speakers are designed specifically to help contribute to your surround sound field. All you need to know, however, are some basics about how they work. Bipole speakers fire their cones to the front and rear (remember, they have drivers on two planes) at the same time and in phase. In other words, the cones go out or in together, in the same direction (both out or both in) and at the same time. Dipole speakers are out of phase with each other. When one side's drivers are pushing out, the other side's drivers are pulling in.
Although the electrical phase in bipoles and dipoles is different, the basic construction of bipoles and dipoles is very similar. You can find speakers on the market that can be both bipoles and dipoles. Most of these speakers have a switch that lets you switch the mode they operate in. Some people prefer music played back through dipoles and movies through bipoles, and these speakers let you make that choice on the fly.