But right now, a home theater, where multi-channel sound is supported by five or six speakers, you will not surprise anyone. More and more often there are cars with systems of "surround" sound, established regularly - at the factory. But many car owners still believe that their four-speaker receivers produce the same “ambient” sound that is so fashionable in the movie industry. Here they are mistaken.
Actually the ambient sound technology came to us from the cinema. And there - their requirements and, therefore, their own history of development.
In order to attract the viewer, the cinema needed more than just a large screen over time … It is natural that by the end of the 50s a panoramic image and stereo sound began to appear - a signal recorded independently for the left and right channels, which allowed to “decompose” the sound into the plane. But the paradox remained in this case: the “movie theater” was supposed to give the maximum effect of presence, and a wide-screen panoramic image was not best combined with a “flat” sound.
The first step towards surround sound was the addition of a “central” channel. We are talking about another column located in the center, which should provide clear dialogs and introduce a better panorama of sound. But simply adding a channel would make it necessary to change all the equipment. They acted differently: the stereo signal was recorded so that with the help of a decoder it was possible to extract sound from it for the central channel.
But still - it was not the sound that would give the effect of presence, volume. Therefore, the next step was the addition of the rear channels. The result is five speakers around the viewer (left, right, left rear, right rear and center channels). The essence is the same: a special stereo signal was decomposed using a decoder into five channels.
In the 80s, a similar standard for surround sound (Surround Sound) entered the mass technique under the name Dolby Pro Logic (Dolby - in honor of the founder) and is still applied.
The next stage of development, of course, is associated with the advent of digital technology and media. Let's say a DVD uses the digital principle of storing audio information. Moreover, it was originally recorded for all channels individually. To date, the most common decoders are Dolby Digital and dts (the latter is characterized by a lower degree of compression of the audio signal).
Frequently encountered notation, for example, “5.1”, means the number of channels: 5 - broadband and 1 - low frequency (simply a subwoofer). Recently, new standards have appeared, for example, “6.1” - they already use the central channel for the rear.
The technology for constructing "ambient" sound in a car is similar to home appliances. You need a sound source, surround decoder, amplifier and wires. Depending on the design, the DVD player can be combined with a decoder or, say, an amplifier with a decoder.
Now about the nuances. To decompose the sound into a “five plus one” channel using an external decoder, you need a DVD player or receiver with digital audio output. If the output is only analog, then surround sound will only allow you to get a Dolby Pro Logic decoder that works with analog stereo sound. But in this case, a loss of quality is inevitable. Dolby Digital and dts decoders work only with a digital signal. That is, at their input - one digital signal, and at the output - individual analog signals for each channel: a complete set of 5.1. The next thing is to strengthen them. Everything is the same as with the usual stereo signal, but there are more amplification channels. If we talk about the decoder as a device, then it can simultaneously have the standard Dolby Digital and dts. As with the DVD itself, sound can be recorded in several formats. The choice of preference is yours.