When it comes to setting up a home theater, your decision should be based predominantly on the size of your room, its acoustics, the number of listeners, and your listening preferences.
Direct-Radiating Speakers
A direct-radiating speaker (sometimes referred to as a monopole) is a forward-firing speaker that outputs sound directly into the room toward the listeners. Surround sound effects in movies, music, and games are most noticeable with direct speakers. In general, most people prefer direct speakers if they listen primarily to multichannel music. The speakers that most people have in a basic stereo setup are typically direct-radiating speakers. When they are used in a surround sound setup, direct speakers are sometimes positioned at the sides or rear of the listening room behind the listeners. Direct-radiating speakers are the go-to choice if the surround-sound setup is for a single listener who can position every speaker equidistant from that single seat.
Bipole Speakers
Bipole surround speakers have two or more speakers that output sound from both sides of the cabinet. If used as side-surround speakers, the sound is output both toward the front and rear of the room. If used as rear-surround speakers, they output sound in both directions along the rear wall. The dual speakers used in a bipole speaker are in phase, meaning that both speakers output sound simultaneously. Bipole speakers create a diffuse surround effect, so the location of the speaker cannot be pinpointed. Bipole speakers are a good choice for movies and music and are usually placed on the side walls. In a large room, bipole speakers and direct-radiating speakers both work well. If you prefer directional sound from the back of the room, bipole speakers deliver from that area.
Dipole Speakers
Like a bipole speaker, a dipole speaker outputs sound from both sides of the cabinet. The difference is dipole speakers are out of phase, which means that one speaker outputs sound while the other doesn’t, and vice-versa. The purpose is to create a diffuse and enveloping surround sound effect. Dipole surround speakers are usually preferred by movie enthusiasts and are positioned on the side walls. In general, dipole speakers positioned at the sides are a good choice for relatively small rooms with good acoustics and multiple seats, where everyone except the person in the middle is sitting close to a speaker.
Choosing Surround Sound Speakers
Some speaker manufacturers such as Monitor Audio and Polk Audio have made your decision a little easier by including a switch that allows you to select bipole or dipole output on the surround speakers. Denon provides dual surround speaker switching on some of its AV receivers, so you can use two pairs of surround speakers, direct and bipole/dipole and switch between them for movies or music.
