The surround sound technology that is possible today is quite literally astonishing, with systems like Dolby Atmos and DTS:X that will make you swear the movie theatre actually exploded when that bomb went off -- it wasn't just on the screen. Even the surround sound systems available in living rooms are impressively immersive, so much so that going to a theatre almost seems obsolete. How did we get such advanced audio technology? Let's take a look at where surround sound started, and how it became what it is today.
A Humble Beginning
The summer of 1969 marked the introduction of surround sound into homes, known as Quadraphonic sound. It made its debut on reel-to-reel tapes, providing discrete sound from four speakers placed in each corner of a room. However, its confusion and limited popularity were due to the ongoing battle between companies over different formats.
Despite this setback, the pursuit of a three-dimensional audio experience persisted, leading to Dolby Laboratories' introduction of Dolby Surround in 1982. This technology utilized matrix encoding to carry a surround sound signal on a stereo source. Since then, companies such as Dolby and DTS have continuously improved home surround sound through a series of advancements. This evolution will be discussed in the following section, starting with the standard 5.1 setups and concluding with the current state-of-the-art object-based surround technology.
Dolby Digital Enters the Playing Field
Do you recall LaserDisc? Although it was first invented in 1978, it wasn't until 1983, when Pioneer Electronics acquired a controlling stake in the technology, that it gained any significant traction in North America. One of the key benefits of LaserDisc was its larger storage capacity compared to VHS tapes. This advantage was seized by Dolby, who created AC-3, now known as Dolby Digital. This format improved on Pro Logic by incorporating stereo surround speakers for higher bandwidth sound and adding a low-frequency effects channel, represented by the ".1" in 5.1, handled by a subwoofer. The information in Dolby Digital 5.1 is discrete for each channel, eliminating the need for matrixing.
The film "Clear and Present Danger" was the first Dolby Digital surround sound to reach home theaters with its release on LaserDisc. By the time DVDs arrived in 1997, Dolby Digital had established itself as the default surround sound format. To this day, Dolby Digital 5.1 is widely regarded as the standard for surround sound and is still prevalent on most Blu-ray discs.
The Competitor: DTS
The technology market is never without competition. For many years, Dolby dominated the surround sound arena. In 1993, DTS entered the scene and offered its own digital surround sound mixing services for movie production, making its debut in theaters with "Jurassic Park". While it eventually made its way to LaserDisc and DVD, it was initially limited to a small selection of discs. DTS utilizes a higher bit rate, delivering more audio information, much like the difference between a 256kbps and 320kbps MP3 file. The quality difference is perceptible, but, like many audio comparisons, not everyone was convinced.
The Next Level: 6.1
In an attempt to improve surround sound by expanding the soundstage, home theater companies introduced 6.1, which added an additional sound channel. The sixth speaker was to be placed in the center of the rear of the room and was referred to as a back surround or rear surround. This is where some confusion started to arise.
Due to their common placement behind a seating area, people had already become accustomed to referring to surround speakers as "rears," even though this was not technically accurate. Proper speaker placement, however, has always recommended placing the surround speakers to the sides and just behind the listening position.
The purpose of the sixth speaker is to give the listener the illusion of audio coming from behind or moving towards the rear. Despite being technically correct, referring to the sixth speaker as a "back surround" or "surround back" speaker only added to the confusion.
The situation became even more complicated with different companies offering different versions of 6.1 surround. Dolby Digital and THX partnered to create a version referred to as "EX" or "surround EX," which utilized the tried-and-true matrix encoding method to embed the sixth channel within the left and right surround signals.
On the other hand, DTS offered two separate 6.1 versions: DTS-ES Discrete and DTS-ES Matrix. As the names suggest, DTS-ES Discrete includes specific sound information programmed onto a DVD or Blu-ray disc, while DTS-ES Matrix uses the same technique as Dolby Digital EX to extract information from the surround channels.
The Introduction of Blu Ray and 7.1
Just as people were becoming familiar with 6.1, 7.1 emerged as the new must-have surround format, largely replacing its predecessor, with the advent of HD DVD and Blu-ray discs. Similar to 6.1, there are several different versions of 7.1, all of which add a second back surround speaker.
The surround effects that were once directed to a single rear surround speaker could now be directed to two speakers in stereo, with each speaker receiving its own specific information, thanks to the massive storage capacity of Blu-ray.
Those who invested in a dedicated back surround speaker during the transition to 6.1 found themselves in the market for a new pair of back surrounds, typically the same model as their left and right surrounds.
Dolby offers two different 7.1 surround sound formats. Dolby Digital Plus is the "lossy" version, which uses lossy compression on all discrete audio channels to save space on a Blu-ray disc, instead of matrixing. Dolby TrueHD, on the other hand, is lossless, meaning no sound information is lost during compression, providing a near-perfect representation of the studio master.
Similarly, DTS also has two 7.1 versions, which are differentiated in the same way as Dolby's offerings. DTS-HD is a lossy 7.1 surround format, while DTS-Master HD is lossless.
It's important to note that not all Blu-ray discs include 7.1-channel surround sound mixes. Movie studios have the option to mix for 7.1, and they don't always choose to do so. There are other factors at play as well, with storage space being a primary consideration. If a disc is filled with extra content, there may not be enough space for additional surround information. In many cases, a 5.1 mix can be expanded to 7.1 using a matrix process in an AV receiver, allowing the back surround speakers to be utilized, even if they don't receive discrete information. However, this is becoming less common, especially with 4K Ultra HD Blu-ray discs, which often support multiple seven-channel mixes.
9.1 and the Return of Pro Logic
If you've been shopping for a receiver, you may have noticed that many offer various versions of Pro Logic processing. The modern Pro Logic family includes Pro Logic II, Pro Logic IIx, and Pro Logic IIz. Let's take a quick look at what each of them does.
Pro Logic II
Pro Logic II uses the same matrixed four-channel sound as the original Pro Logic and can create a 5.1 surround sound mix from a stereo source. Additionally, Pro Logic II has the capability to separate the surround signal into stereo left and right channels, instead of the original Pro Logic's dual-mono presentation. This processing mode is frequently used when watching non-HD TV channels with a stereo-only audio mix.
Pro Logic IIx
If your video source is presented in 5.1 surround and your home theater system supports additional speakers, Pro Logic IIx can expand the mix to 6.1 or 7.1. Pro Logic IIx is divided into movie, music, and game modes.
Pro Logic IIz
Pro Logic IIz allows for the addition of two "front height" speakers positioned above and between the main stereo speakers. This form of matrix processing aims to add more depth and space to a soundtrack by emitting audio from a new location in the room. When engaged with a 7.1 soundtrack, the resulting format can be referred to as 9.1.
Although the height channels are added, Pro Logic IIz does not enable true 3D placement of sounds. To achieve that, you need Dolby Atmos or DTS:X, which will be described later.
2 Sub Systems
As previously mentioned, the ".1" in 5.1, 7.1, etc. refers to the LFE (low-frequency effects) channel in a surround soundtrack, which is handled by a subwoofer. Adding ".2" simply indicates that a receiver has two subwoofer outputs instead of one. Both connections output the same information, as there is only one subwoofer track according to Dolby and DTS. The addition of a second subwoofer output was marketed by AV receiver manufacturers, leading to the use of ".2."
For most people, a single subwoofer provides enough low-end bass and rumble. However, adding a second subwoofer can enhance the effect, especially in larger media rooms. Check out our subwoofer placement guide to determine if a second subwoofer might be right for you.
Audyssey DSX
Audyssey, a company known for its auto-calibration software found in many modern AV receivers, has its own surround solution called Audyssey DSX. DSX enables additional speakers beyond the core 5.1 and 7.1 surround formats by upmixing 5.1 and 7.1 signals to add more channels. By adding front width and front height channels to a 7.1 system, Audyssey allows for 11.1 channels of surround sound.
There is also Audyssey DSX 2, which upmixes stereo signals to surround sound. However, with the rise of object-based 3D formats like Dolby Atmos and DTS:X in recent years, Audyssey has seen a decline in popularity.
Object-Based Surround Sound
As previously mentioned, the latest advancement in surround sound is referred to as "object-based" or "3D" surround. For viewers, "3D" is the best description of this technology due to its ability to make sounds seem as if they are moving through space. For example, you might hear a helicopter taking off in front of you, hovering over your head, and then disappearing into the distance behind you.
"Object-based," on the other hand, is the terminology preferred by sound professionals who create these 3D soundtracks, as it describes their ability to place a single sound-producing object, such as a helicopter, anywhere in 3D space.
This 3D sound experience is achieved by adding discrete channels for ceiling-mounted or ceiling-facing speakers in home AV receivers.
These channels no longer need to extrapolate their signals from audio sent to other speakers, as was the case with Pro Logic IIz 7.1, and are therefore given their own number. For example, a 5.1.2 system features the traditional five channels and a subwoofer, but it also has two additional speakers that provide stereo height information at the front. A 5.1.4 system adds four additional height channels to 5.1, including two at the front and two at the rear, and so on.
Modern Flagship: Dolby Atmos
As you may have guessed based on the rest of the article, Dolby is currently the leading provider of object-based surround sound technology. While we've discussed how Atmos aims to revolutionize the movie theater experience, what about in the home theater setting?
Atmos was introduced on compatible AV receivers in 2015, but with limited capabilities compared to the professional format. As previously discussed, the most common configurations are 5.1.2 or 5.1.4, which add two or four height speakers to a traditional 5.1 setup respectively, although Dolby supports larger configurations. Atmos quickly gained popularity and now most AV receivers, even those priced at $500 or less, support the format.
In 2015, Yamaha introduced the first Atmos-capable soundbar, the YSP-5600, which utilized up-firing drivers to reflect sound off the ceiling. Since then, soundbar manufacturers have widely adopted Dolby Atmos. Some achieve the Atmos effect through dedicated wireless surround speakers with up-firing drivers to complement the front speakers in the soundbar. Others utilize virtualized Dolby Atmos, a technique that effectively simulates the Atmos effect with fewer speakers.
The availability of Dolby Atmos in home theaters has increased rapidly since its debut in 2015, with most high-end AV receivers now supporting the format. Even some soundbars and TVs claim to support Dolby Atmos through their built-in speakers, though a true Atmos experience requires more than just two channels.
Atmos-enabled movies and shows are now widely available on Blu-ray and Ultra HD Blu-ray discs, as well as streaming sites like Netflix, Amazon Prime Video, Disney+, and Apple TV+. Live events, such as the 2018 Winter Olympics and music festivals, have also featured Dolby Atmos sound.
However, it's important to note that a complete Dolby Atmos setup requires support from all components of the home theater system, from the source to the speakers. To fully experience Atmos sound, it's recommended to follow a comprehensive guide to getting great Dolby Atmos sound.
Dolby Atmos Music
Although still in its infancy, Dolby Laboratories has been working with major music labels and streaming services to integrate Dolby Atmos technology into music production. Using the same object-based 3D audio tools as in the movie soundtrack version, professional music producers are able to create an immersive audio experience beyond traditional stereo or quadraphonic sound. However, access to Dolby Atmos Music is currently limited and can only be heard using a Dolby Atmos-enabled home theater system through the purchase of select Blu-ray discs with Dolby Atmos Music mixes, such as the remastered version of INXS's "Kick."
Amazon Music HD made history as the first music streaming service to offer Dolby Atmos Music tracks, but they can only be enjoyed on Amazon's Echo Studio 3D smart speaker. In a limited number of clubs, Dolby Atmos Music is being used to create an immersive sound experience for live performance and dance floors. Although the options for listening to Dolby Atmos Music are currently limited, it is hoped that it will soon become more widely available. Additionally, Sony has its own 3D immersive music format called Sony 360 Reality Audio, which is also available on some streaming services, but the devices capable of playing it are currently limited.
It's expected that Dolby will soon make Dolby Atmos Music more accessible, allowing more people to enjoy the immersive music experience.
It's important to note that Sony has its own 3D music format called Sony 360 Reality Audio, which is a competitor to Dolby Atmos Music. This format is also available on some streaming services, but the number of devices capable of playing it is currently limited.
DTS:X
DTS has its own form of object-based audio, known as DTS:X, which was also introduced in 2015. Unlike Dolby Atmos, DTS:X aims to be more versatile and approachable, utilizing existing speaker setups in theaters and supporting as many as 32 speaker configurations in homes.
While in the past, DTS:X was added as an update to Atmos-compatible AV receivers, it is now available in newer AV receivers from the get-go. Despite its lack of widespread adoption on physical media and its absence on streaming services, some studios like Lionsgate and Paramount offer home releases in DTS:X.
DTS Virtual:X
DTS understands that not everyone has the room or resources to create an object-based audio setup. Based on their research, only 30% of customers actually have height speakers connected to their systems, with less than half even connecting surround speakers.
To address this, DTS created DTS Virtual:X, which uses digital signal processing (DSP) to deliver the same spatial effects of a traditional DTS:X system, but with fewer speakers, even if you only have two. This technology was initially introduced in soundbars, as they often have a subwoofer and a pair of satellite speakers at most. Since then, companies such as Denon and Marantz have incorporated DTS Virtual:X into their receivers, while Sony has its own virtual surround soundbar that can play DTS:X and Atmos soundtracks.
Technically, virtualized Dolby Atmos and DTS Virtual:X share similarities, however, Dolby doesn't make a distinction between different implementations of Atmos. From their perspective, Atmos is simply Atmos, whether it's produced through two, three, five channels or through a full, discrete 5.1.2 or more speaker system.
Other Competitors: Auro-3D and MPEG-H
Auro-3D was introduced prior to the arrival of DTS:X and Atmos. It was first announced for use in theaters in 2006, but was not accessible for home theater systems until companies like Denon and Marantz made it available as a paid firmware upgrade.
Despite its similarities to Dolby Atmos, Auro-3D creates an immersive sound experience through a three-level speaker system. To fully experience this layered sound, eleven speakers are recommended, making it the priciest setup for a home theater. Due to its reliance on a single overhead channel, Auro-3D's speaker configurations may not be optimal when used in conjunction with Dolby Atmos sound.
Although Auro-3D has yet to gain widespread popularity in the United States, it has a strong presence in Europe and Japan and is likely to grow in popularity in the future.
MPEG-H is a suite of audio and video standards, with a key component being its support for 3D Audio. Similar to Dolby Atmos, it enables developers to place a large number of audio objects in a three-dimensional space. This versatile standard also gives users the ability to manipulate individual sound elements, such as dialogue or sound source. To learn more, check out our comprehensive guide to MPEG-H.
While not widely used in North America, MPEG-H is available on broadcasts in Brazil and South Korea, and can be found in home theater products from brands like Denon and Marantz. As the standard gains popularity, particularly in the realm of broadcasts, it could become a sought-after option for experiencing live TV with 3D audio.
IMAX
IMAX Enhanced, the more recent standard in home theater surround sound, is known for its visual enhancements and its aim to imitate IMAX Signature Sound in a home theater. The visual enhancements reformat the compatibility in movies and turn off other image optimizations to make it seem like you're watching it in IMAX, even expanding the aspect ratio. It uses a part of the DTS:X codec to achieve deep bass, similar to IMAX theaters. However, it's still a new standard and may not make an impact on home theaters for a few years. It's worth noting that not all content that claims to be IMAX Enhanced has the DTS:X audio improvements, only the visual changes, which can be problematic for titles like Disney+'s IMAX Enhanced Marvel movies.
Creating a home theater system with studio-quality sound is now more accessible than ever. With advancements in "3D" or "object-based" surround sound and the integration of dedicated speakers into the traditional 5.1 setup, you don't have to be a sound expert to achieve an immersive audio experience. A bit of research can go a long way in determining what's best for you. So, keep this guide close by as you set up your system and you'll have no trouble creating a top-notch audio experience.
