Surround sound is aptly named for surrounding the listener with an acoustic environment that goes beyond the two-channel stereo experience of the past. In both public and home theaters, the systems project sound all around the listener, providing a more natural experience.
In real life, people experience sound in the context of ambient noises. If someone is talking, the listening might also hear the faint drone of a jet far above, a schoolyard full of children nearby, birds in the trees, and a television blaring from the next room. These sounds are spread throughout the audible landscape. Surround sound faithfully recreates an entire landscape by sending the right sounds to the right places to simulate an experience closer to real life.
The first incarnation was surround sound 5-1, which included five speakers and one subwoofer for delivering bass sounds. This is also referred to as Dolby Digital and Digital Theater Systems (DTS) sound.
Next came DTS Extended Sound (DTS-ES) or THX as surround sound 6-1. This system uses six speakers plus a subwoofer, with that additional speaker taking the position of center rear to create a more complete three-dimensional soundscape. The 7-1 system adds yet another speaker to the mix: it takes the rear center channel and divides it in two, creating flanking speaker positions for an encircled rear.
While a stereo recording will play through any surround system, the receiver will simply send the left channel to half of the speakers and the right channel to the other half. To get the full effect, the original recording must be encoded for it. When this is the case, the receiver is able to send specific sounds to specific speakers, creating “placed sounds” to build an acoustic atmosphere.
For example, a person can imagine watching a movie in which the main character is standing on the sidewalk when he hears his friend call his name just behind him. He turns to his left and sees his friend. Watching this movie in surround sound, the friend’s voice will come from the rear left speaker, placing the viewer inside the sound track.
The greater number of speakers a surround system has, the greater its ability to place sounds where they belong. The difference becomes clear when, for example, watching a war scene with munitions exploding all around. This system will have the viewer feel like bullets are whistling by and jumping at bombs exploding behind his back. Compare this to the entire sound track playing through two front speakers in a stereo system. The more complicated system adds authenticity because it puts the viewer or listener inside the action of the picture, or in the case of music, on stage with the band encircling him.
Surround sound systems have minimum requirements for amperage generated by the receiver. If the receiver is not powerful enough, it won’t be able to push the sounds through the speakers with sufficient gusto. If the receiver has far more power than the speakers require, it will be very easy to blow the speakers out by accidentally leaving the volume up when powering up the system. Users also need to be sure that the receiver supports the number of speakers, since one that only supports 5-1 will not work correctly with 6-1 or 7-1 speaker systems.
