Since the mid-1990s, surround sound has been an integral part of the home theater experience and, with that, there is an abundance of surround sound formats to choose from.
The Big Players in the Surround Sound Landscape
The main players in the surround sound landscape are Dolby and DTS. However, there are others. Most home theater receiver producers have additional third-party partnerships with one or more companies that offer their own twists to enhance your surround experience.
What You Need to Access Surround Sound
You need a compatible home theater receiver supporting a minimum 5.1 channel speaker system, an AV preamp/processor paired with multi-channel amplifier and speakers, a home-theater-in-a-box system, or a soundbar to experience surround sound. However, the number and type of speakers or the soundbar in your setup is one part of the equation. To get the benefit of surround sound, you also need to access the audio content that your home theater receiver, or another compatible device, can decode or process.
Surround Sound Decoding
One way to access surround sound is to use an encoding/decoding process. This process requires the surround sound signal to be mixed, encoded, and placed on a disc, streamable audio file, or another type of transmission by the content provider (such as a movie studio). The player or streamer sends the encoded signal via a digital optical/coaxial or HDMI connection to a home theater receiver, AV preamp processor, or another compatible device that decodes the signal and distributes the signal to the appropriate channels and speakers so that you can hear it.
Surround Sound Processing
Another way to access surround sound is with surround sound processing. This is different than encoding/decoding. Although you need a home theater, AV processor, or a soundbar to access it, it doesn’t require any special encoding process on the front end. Surround sound processing is accomplished by the home theater receiver reading the incoming audio signal (which can be analog or digital) and then looking for embedded cues that indicate where those sounds might be placed if it were in an encoded surround sound format. Although the results are not as accurate as surround sound that uses an encoding/decoding system, it provides an acceptable surround sound experience for most content. Most surround sound processing formats can take any two-channel stereo signal and upmix it to four, five, seven, or more channels. Some surround sound processing formats included on many home theater receivers and other compatible devices include:
Dolby Pro-Logic: Up to four channels.Pro-Logic II: Up to five channels.Pro-Logic IIx: Can upmix two-channel audio up to seven channels or upmix 5.1 channel encoded signals up to 7.1 channels.Dolby Surround upmixer: Can upmix from two, five, or seven channels to a Dolby Amos-like surround experience with two or more vertical channels.
On the DTS side, there is DTS Neo:6 (can upmix two or five channels to six channels), DTS Neo:X (can upmix two, five, or seven channels to 11.1 channels), and DTS Neural:X (which functions in a similar fashion as the Dolby Atmos upmixer). Other surround sound processing modes include:
Audyssey DSX: Expands a 5.1 channel decoded signal by adding an extra-wide channel or front height channel or both. Auromatic by Auro3D Audio: Works in a similar fashion as the Dolby Surround and DTS Neural:X upmixers.
In addition to the surround sound decoding and processing formats above, some home theater receivers, AV processors, and soundbar makers add formats such as Anthem Logic (Anthem AV) and Cinema DSP (Yamaha).
Virtual Surround
While the above surround decoding and processing formats work great for systems with multiple speakers, something different needs to be employed with soundbars. This is where virtual surround sound comes in. Virtual surround sound enables a soundbar or other system (sometimes offered in a home theater receiver as another option) that provides surround sound listening with only two speakers (or two speakers and subwoofer). Known by several names (depending on the soundbar brand) Phase Cue (Zvox), Circle Surround (SRS/DTS–Circle Surround can work with both un-encoded and encoded sources), S-Force Front Surround (Sony), AirSurround Xtreme (Yamaha), Dolby Virtual Speaker (Dolby), and DTS Virtual:X. Virtual surround operates in one of two ways. It can take a two-channel signal and give a surround sound-like treatment. Or, it can take an incoming 5.1 channel signal, mix it down to two channels, and then use those cues to provide a surround sound experience using the two available speakers it has to work with.
Ambiance Enhancement
Surround sound can be further complemented with the implementation of ambiance enhancement. On most home theater receivers, added sound enhancement settings are provided that can add ambiance to surround sound listening, whether the source content is decoded or processed. Ambiance enhancement has its roots in the use of reverb to simulate a larger listening area back in the 1960s and 1970s (used a lot of in-car audio) but could be annoying. The way that reverb is implemented these days is by the sound or listening modes provided on many home theater receivers and AV processors. The modes add more specific ambiance cues tailored for specific content types or simulate the acoustic properties of specific room environments. There may be listening modes provided for movie, music, game, or sports content. And, in some cases, it gets more specific (sci-fi movie, adventure movie, jazz, rock, and more). Some home theater receivers also include settings that simulate the acoustics of room environments, such as a movie theater, auditorium, arena, or church. The final touch available on some high-end home theater receivers is the ability to tailor the pre-set listening mode and ambiance settings manually to provide a better result by adjusting factors such as room size, delay, liveness, and reverb time.
