An audio or home theater system generally includes the center channel speaker, the left and right front speakers, the surround channel speakers, and the subwoofer.
The purpose of the center speaker is to provide highly localized speaker information; it's coming from the center of the screen. There's a high correlation between what you see on the screen and where the sound comes from. The left and right speakers are to provide more lateral, but still highly localized and directed, sound. Together, the three represent the frontal face of your home theater sound experience. When there is a specific sound — the clash of swords, the shout of the main character, the click of a trigger being pulled back — the sound comes predominantly from these speakers.
Center speakers
The center speaker is probably the most important speaker in your system, but it's optional. This is because the left and right speakers can handle the sound that comes from the center speaker. However, you may miss out on a lot if you choose to omit a center speaker from your audio system.
The center speaker anchors your on-screen dialogue and serves as a seamless connection between your left and right speakers. As that boat zooms by left to right, you don't want to have a gap in the middle of your soundfield (a concern as screens get larger and larger). Center speakers are usually located behind the screen or above or below displays, so that you can localize the on-screen sound as much as possible.
To achieve this seamless harmony with the left and right front speakers, your choice of center speaker is important. Don't skimp on the center speaker in favor of your other front speakers. Each speaker (left, center, and right) is equally important and should be of similar size, similar capability, and preferably come from the same manufacturer. In fact, if you can use an identical model speaker for the center, left, and right speakers, do it. Many folks can't do this because they've chosen tower speakers for their left and right speakers, and can't possibly install a tower speaker on top of their display as a center channel speaker. If you're not using dipole or bipole speakers for your surround channels, you should consider using another identical pair of speakers for your surrounds as well.
Make sure any speakers that will be close to a cathode ray tube (direct-view) video display are video shielded — especially the center speaker. If not, the speakers will cause picture distortions on your screen. This is most important for your center speaker (which may rest directly on top of your display), but can also be an issue for your left and right speakers if they too are close to the display.
Left and right speakers
The front left and right speakers, if possible, should be:
- Full-range speakers (even if you plan on using a subwoofer).
- Ear-level (even if using bookshelf-style speakers). If the speakers are large, keep the tweeters at ear level.
- Of similar performance capability as the center speaker — preferably from the same manufacturer.
If you want to use your existing speakers with your audio system, try to buy a center speaker from the same manufacturer and class for the best results. In an ideal world, you use exactly the same model of speaker for your center, left, and right speakers — all your front speakers. You should try to buy all three of these speakers from the same manufacturer and make sure that the manufacturer has designed them to be timbre matched — in other words, that they sound alike. This ensures that you get a more seamless listening experience.