It was the summer of '69. We are not talking about the song by Bryan Adams here; we actually refer to the first time surround sound became available at home. It was called Quadraphonic Sound and it first appeared on tape from reel to reel. Unfortunately, the quadraphonic sound, which delivered a discreet sound from four speakers placed in every corner of a room, was confusing and short-lived – not thanks to companies vying for formats (sounds familiar?).
Immersion in a three-dimensional audio sphere, however, should not be abandoned. In 1982, Dolby Laboratories introduced Dolby Surround, a technology that transports a surround sound signal to a stereo source through a process called matrix encoding. Since then, Dolby, DTS and others with different iterations have improved the state of home surround sound. With so many options, the technology remains confusing to many. From standard 5.1
to Dolby Atmos setups with multiple overhead speakers, turning your head is a lot. Our detailed guide aims to provide a bit of clarity to help you in your quest for surround sound.
Surround sound 101
Surround sound, in its most basic form, includes a set of stereo front speakers (left and right) and a set of surround speakers, which are usually just at the sides and just behind a central listening position are placed. The next step is the addition of a center channel: a speaker between the left and right front speakers that is primarily responsible for displaying dialogues in movies. So there are five speakers involved. We'll add more speakers later (much more actually), but for now, we can use this simple five-speaker setup as a springboard to get into the different sizes.
For the purposes of this discussion, "matrix" has nothing to do with the Keanu Reeves. In this case, matrix refers to the encoding of individual audio signals within a stereo source. This approach was the basis for early surround sound formats such as Dolby Surround and Dolby Pro Logic and was partly motivated by the limited space for discrete information on early audio-video media, such as the VHS tape.
Pro Logic  Using the matrix process, Dolby & # 39; s Pro Logic surround has been developed to encode separate signals within the left and right channels. Dolby was able to allow home audio devices to decode two additional sound channels from media such as VHS tapes, which supplied the center channel and surround speakers with audio. Due to the limited space, matrix surround signals came with some limitations. The surround channels in standard Pro Logic were not in stereo and had limited bandwidth. That means each speaker played the same and the sound didn't contain much bass or treble information.
5.1: Surround takes shape
Dolby Digital 5.1 / AC-3: The benchmark
Remember LaserDisc? Although the medium was first invented in 1978, it was not until 1983 when Pioneer Electronics acquired a majority stake in the technology that had some form of success in North America. One of the advantages of LaserDisc (LD) is that it offered much more storage space than VHS tape. Dolby took advantage of this and created AC-3, now better known as Dolby Digital. This format improved over Pro-Logic by allowing stereo surround speakers that could deliver higher bandwidth sound. It also facilitated the addition of a low-frequency effect channel, by adding the ".1" in 5.1, which is handled by a subwoofer. All information in Dolby Digital 5.1 is separate for each channel – matrix formation is not necessary.
With the release of Clear and Present Danger on LaserDisc, the first Dolby Digital surround sound entered the home theater. By the time DVDs came out in 1997, Dolby Digital had become the standard format for surround sound. To this day, Dolby Digital 5.1 is considered by many to be the standard for surround sound, which is still found on most Blu-ray discs.
Image courtesy of Dolby
DTS: The Rival
What is a technology market without a bit of competition? Dolby more or less dominated the surround sound landscape for years. Then, in 1993, DTS (Digital Theater Systems) came by, providing its own digital surround sound mixing services for film production, and visiting theaters for the first time with Jurassic Park . The technology eventually trickled down to LD and DVD, but was initially available on a very limited selection of discs. DTS uses a higher bit rate and therefore provides more audio information. Think of it as the difference between listening to an MP3 file at 256 kbps and 320 kbps. The quality difference is noticeable, but as with so many audio-related comparisons, not everyone is sold on it.
6.1: Taking it up a notch
In an attempt to improve the surround sound through the & # 39; soundstage & # 39; expand 6.1 has added another sound channel. The sixth speaker would be placed in the center of the back of a room and was later called a rear surround or rear surround. This was where a lot of confusion started to revolve around surround sound.
People were used to seeing (wrongly) surround speakers as "rears" because they were so often seen behind a sitting area. However, the recommended speaker placement has always resulted in surround speakers being placed on the sides and just behind the listening position.
The purpose of the sixth speaker is to give the listener the impression that something is approaching from the rear or disappearing to the rear. Calling the sixth speaker a "back surround" or "surround back" speaker, while technically accurate, was just confusing.
To make it even more confusing, each company offered different versions of 6.1 surround. Dolby Digital and THX have teamed up to create a version called "EX" or "Surround EX". It uses the proven matrix encoding method to embed the sixth channel in the surround left and right signals.
DTS, on the other hand, offered two separate 6.1 versions. DTS-ES Discrete and DTS-ES Matrix perform as their name suggests. ES Discrete programs specific sound information onto a DVD or Blu-ray disc, while DTS-ES Matrix uses the same technique as Dolby Digital EX to extrapolate information from the surround channels.
7.1: The Spawn of Blu-ray
Just as people were getting used to 6.1, 7.1 came along with HD DVD and Blu-ray discs as the new indispensable surround format, which essentially replaced its predecessor. Like 6.1, there are several versions of 7.1, all of which add a second surround back speaker.
The surround effects that once went to just one surround back speaker could now go to two speakers in stereo. The information is discreet, which means that each speaker gets its own specific information – we can thank the enormous storage potential of Blu-ray for that.
Those who bought a dedicated back surround speaker now found themselves looking for a new matching pair of rear surrounds – typically the exact same model they'd bought for the left and right surrounds.
Dolby offers two different 7.1 surround versions. Dolby Digital Plus is the & # 39; lossy & # 39; version. Rather than using matrixing, lossy compression is applied to all individual audio channels, which helps take up less space on a Blu-ray disc. Dolby TrueHD, on the other hand, is lossless. Since no compression is involved, Dolby TrueHD is intended to be identical to the studio master.
DTS also has two 7.1 versions, which differ in the same way as Dolby & # 39; s versions. DTS-HD is a lossy, compressed 7.1 surround format, while DTS-Master HD is lossless and is intended to be identical to the studio master.
It is important to note that 7.1 channel surround mixes are not always recorded on Blu-ray discs. Movie studios should choose to mix before 7.1, and they don't always do. Other factors are also involved. Storage space is the most important among them. If a lot of extras are placed on a disc, there may not be room for the extra surround information. In many cases, a 5.1 mix can be expanded to 7.1 through a matrix process in an A / V receiver. This way those rear surround speakers get used to it, even if they don't get discrete information. However, this is becoming less and less common, especially when it comes to 4K Ultra HD Blu-ray discs, which often support multiple seven channel mixes.