The more you know…
Thanks to MrAudioSoundImages you will know more about the origins of the surround sound formats used in films.
As early as 1952 the film “This is Cinerama” had a 7-channel surround soundtrack.
In the early 70’s, quad sound, a 4.0 format was available for a very short period.
In 1977, Star Wars Episode IV was the first film to have a Dolby Pro-Logic soundtrack, with left, center, right, and surround. It was basically a 3.9, since the surround channel topped off at 7 kHz.
In 1992, Batman Returns, had the first Dolby Digital 5.1 soundtrack with left, center, right, left surround, right surround, and low-frequency effects tracks.
George Lucas developed a 6.1 system that added a center rear to the standard 5.1, so that starships flying from rear to front could be centered in the theater. This format is also known as EX or DTS ES.
Omnimax and iMax films use a 6.0 speaker system that adds a high center speaker, called “top of screen” to the standard 5.1 and eliminates the dedicated low-frequency effects track. Bass management redirects low-frequency sound from all six channels to the subwoofer.
For SDDS (Sony Dynamic Digital Sound) Two additional front speakers, a left-center, and right-center, are added to the standard 5.1 to produce 7.1 surround.
There’s also a variation of 7.1 where the two added speakers are placed on the sides (as opposed to the front). This is known as 3 / 4.1.
THX creator Tomlinson Holman introduced 10.2 surround that includes the rear center from 6.1, two additional side speakers from the 3 / 4.1, a left and right top of screen speaker, similar to the iMax scheme, and also adds a second subwoofer.