Surround Sound Basics
You can't talk surround sound without first talking about some of the terminology. We'll start you off with some of the basics and then try to redirect you to the more advanced stuff. Alternately, you can visit our surround sound terms section, and have a look around there.
2.0 – This is the conventional stereo format that provides dimensional sound instead of monaural. As indicated, it has two channels, both a left and right.
5.1 – Developed to enhance the viewing experience of movies, this surround sound format is now widely used in movies, music, games, television, and other entertainment mediums. 5.1 surround sound is characterized by five main channels and an LFE (low-frequency effects) channel (bass). The five main channels are left, center (front), right, rear-left, and rear-right.
6.1 – Similar to 5.1, 6.1 surround sound adds an additional center channel to the rear of the arrangement. This gives it left, center (front), right, rear-left, center (rear), and rear-right.
7.1 – Improving the spatial dimension of your theater setup, 7.1 surround sound integrates another two rear channels into the traditional 5.1 arrangement. Although DVDs are not encoded with the extra 2 channels, the 2 back channels are derived from the other channel sources. The real benefit of 7.1 is in movie enhancement rather than music.
You can't talk about surround sound without talking about Dolby. Dolby revolutionized the entertainment industry with its evolutionary surround sound technologies.
Dolby Surround – Introduced in 1982, Dolby surround is encoded with left, center, right, and a monophonic rear sound channel. The innovative thing about this technology was that it was capable of playing in stereo on normal devices, but would output to four channels with a Dolby surround enabled decoder device. The more modern implementation of this is called Dolby Pro Logic.
Dolby Pro Logic II – Introduced in 2001, just about all surround sound decoders sold in the past decade include Dolby Pro Logic II. The primary improvement to the surround sound is that it decodes the speakers in full-bandwidth stereo, providing a more complete rear sound field.
Dolby Pro Logic IIx – Dolby improved upon their technology by allowing any signal type (stereo, 5.1, 6.1, etc…) to be played across all seven of your speakers. So even if your media is not yet capable of 7.1, you can still utilize all of your equipment.
Dolby Digital – This is a lossy audio compression format that allows for up to 6 channels (see 5.1). It is the sound format used on most DVDs, game consoles, cable, satellite, and movie theaters. The vast majority of films are encoded with Dolby Digital.
Dolby Digital EX – Uses a center-rear channel to make the 6.1 standard. The first use of this technology was based on films with THX licenses. THX certified equipment and media are encoded with the extra channel of surround sound.
Dolby Digital Live – Used in video games to convert the signal to 5.1 and then transmit it over a S/PDIF cable.
Dolby Digital Plus – Dolby has continued to improve their technology. Dolby Digital Plus provides better encoding, increases the bit rate, provides backward compatibility, and adds up to 13.1 discrete channels.
Dolby TrueHD – This is a lossless format that can also produce up to 13 discrete channels plus the LFE channel (see 7.1). This is commonly used in HD-DVD and Blu-ray discs. Although HDTV is still not ready to implement this format because of bandwidth issues, you'll find many Blu-ray discs and players are providing their product in this format.
DTS – Although Dolby has the clear market lead, DTS (Digital Theater System) is also in the surround sound encoding market. DTS Digital Surround provides 5.1 channels of digital sound at a lower compression than Dolby. This arguably makes DTS a better sound quality that Dolby, although at the cost of space on the media. While DVDs in North America are required by NTSC to include Dolby Digital or a PCM, DTS is optional.
