What are speaker systems terms ?

Speaker Systems Terms

Dipolar Surrounds
Special rear speakers, referred to as Dipoles, are normally placed to the left and right of the listener and radiate sound in a figure eight pattern. The front and back lobes of sound are acoustically out of phase with one another thus placing the listener in an acoustic null. Depending upon your room and your particular system, dipolar surround speakers may achieve a more realistic and seamless surround effect.

LCR (Left, Center, Right loudspeakers)
Every home theater system requires a left, center, and right loudspeaker. These are sometimes referred to as LCRs. The left and right speakers are situated at the far left and right of the projection screen (or beside the TV or rear projection set), while the center channel speaker is situated in the center of the screen (or on top of the TV or rear projection set). Although it is now possible for movie producers to pan audio effects, music, and dialogue to any of the speakers independently, the left and right speakers normally play back effects and music, while the center channel's purpose is primarily dialogue. With Dolby Digital playback systems it is also important that each of the three front speakers are identical models or share the same tonal response.

Rear
Rear speakers in a home theater surround system are normally located behind the listener and are designed to create the illusion that you are acoustically in the middle of the action that is present on your video screen. The placement of these speakers is critical for achieving proper balance and seamless transitions between front and back "panning" of sounds. In most systems only two speakers are required; however, with Dolby Digital surround sound formats the frequency response and tonal quality of the rear speakers should match that of the LCR speakers in your system.

Sub-Woofer
Sub-woofers are special loudspeakers that reproduce audio frequencies that are usually below 120 Hertz. Approximately 80% of the power required to reproduce sounds like explosions are in the frequency bands below 120 Hz. By utilizing a dedicated sub-woofer you are able to increase the performance of your audio system in several ways. Since many sub-woofers include an integral power amplifier, and allow you to remove the low frequency content from the left and right speakers, the A/V receiver or amplification system will now have more power available for the left and right speakers. Sub-woofers are available in many woofer sizes and power ranges and should be selected according to your room size and sound pressure level (SPL) requirements.