Ultimate Guide To Surround Sound (And How It Works)

There was a time, not so long ago, when most of us were perfectly content with our 32-inch CRT screens and their tinny, built-in speakers. However, with the proliferation of affordable audio-visual gear and the development of new technologies, our standards as consumers have shifted. While surround sound used to be a novel feature reserved for cinemas and pro audio setups, it is now a common fixture in home entertainment systems everywhere.

Surround sound is just that: an immersive sonic experience for audio-visual entertainment, where sound is directed from all angles on a horizontal plane and, increasingly, from above, as a three-dimensional soundscape. This greatly improves the experience for the audience, as it places them front and center within the action, as the soundstage is divided into several distinct channels that better imitate a real live setting.

Here is our ultimate guide to surround sound, covering how it came into being, the many different surround sound configurations, and new and emerging technologies, including Dolby Atmos and DTS:X. We will also explain how surround sound facilitates such realistic and intricate sound reproduction and look at where the technology is headed in the future.

Surround sound is achieved by manipulating audio via various receiver and speaker configurations to create an immersive experience. These usually comprise a central speaker, several satellite speakers, and one or more subwoofers. The AV (audio-visual) receiver is an amplifier, similar to that on a home stereo system, that can divide the signal into as many as 13 distinct channels.

Surround sound setups typically involve a numerical descriptor for the distribution of their channels, such as "5.1" for the number of ear-level speakers relative to the number of subwoofers, which is a single unit in most home setups. Sometimes, in more complex systems, there is a third number, denoting height speakers, which are usually placed in the ceiling or are upward-firing, for example, in 7.1.2 systems.

While researching surround sound setups, you will come across many different configurations, including 2.1, 5.1, 6.1, 7.1, 9.1, and 11.1, as well as twin subwoofer systems, such as 5.2. Where a subwoofer is absent from the configuration, it is described with a zero, as with 5.0 systems. The subwoofer caters to the lower frequencies of 20 Hz to 200 Hz. It is usually positioned anywhere in alignment with the forward-facing speakers, as it doesn't need to be placed centrally within the stereo field. However, it is worth experimenting to fine-tune your home surround sound setup and find the optimal subwoofer location according to the size and shape of the room you plan to use.

[Featured image by Dirrtyjerm via Wikimedia Commons | Cropped and scaled | CC BY-SA 4.0]

The march of technology never falters, and it wasn't long before improvements were sought to widen the soundstage of the 5.1 standard. The next step on surround sound's evolutionary ladder was 6.1 surround, which placed an extra rear speaker between the inward-facing left and right satellite speakers. This added an extra dimension on a horizontal plane, helping the audience gauge proximity as objects approached and retreated from behind the viewer.

While this appeared to be the natural progression for surround sound configurations, it proved confusing when brought to market, as manufacturers vied to create their own formats for 6.1 surround sound. Dolby Digital and THX combined resources to bring us Dolby Digital EX, which extrapolated the extra channel from the rear left and right speaker signals, whereas DTS produced encoded DTS Matrix, which worked similarly to Dolby Digital EX and DTS Discrete, creating a distinct sixth channel.

While 6.1 surround sound was an important stage in the development of modern surround sound, it was short-lived. Already, plans were being made for the next phase of eight-channel surround sound. Nowadays, seven-channel 6.1 systems have been largely consigned to history.

With advances in encoding, better sound reproduction was now possible across multiple channels. However, as attractive as "one format to rule them all" may sound, it was not practical, as the amount of usable data was limited by streaming bandwidth or the available space on a Blu-ray disc. As such, the main developers of surround sound, Dolby and DTS, were forced to split their products into compressed and uncompressed formats.

Lossy formats have lower bitrates and, as such, are better for streaming video, as too much data can lead to interruptions from buffering. To this end, Dolby and DTS created Dolby Digital Plus and DTS-HD, respectively. While these provide higher bitrates and superior surround sound compared to their 5.1 counterparts, Dolby Digital and DTS 5.1, they pale in comparison to the lossless formats Dolby TrueHD and DTS-HD Master Audio. For example, Dolby Digital Plus has a maximum bitrate of 6 Mbps, compared to 18 Mbps for Dolby TrueHD.

It may take a particularly sharp pair of ears to discern the difference between lossless and lossy surround sound. However, it is a testament to the progressive nature of the industry-leading audio encoding companies, Dolby and DTS, that they strive for perfection while providing a practical solution to the data limitations faced by surround sound technology.

There are many factors to consider when choosing the ideal surround sound setup for your living space. These might include your room shape and size, budget constraints, and practical considerations, such as seating. If space and affordability are your chief concerns, Dolby Atmos and DTS:X soundbar/subwoofer combinations offer compact solutions that are often more affordable than a multi-speaker setup. Lots of major brands make soundbars, and the hardware has improved a lot in recent years.

If you decide to go for a fully immersive multi-speaker surround sound system, finding the ideal speaker placement can be a real headache, but it's very important. A typical surround sound setup can be divided into five elements: front speakers, surround speakers, rear speakers, height speakers, and subwoofer.

The front speakers do most of the hard work, and these should be placed at ear level, with the center speaker in the center (of course), and the left and right at around 30 degrees from the central seating position. The subwoofer should be placed in alignment with the front speakers. The surround speakers should be placed at ear level and face the listener from each side.

The rear speakers should also be elevated to ear level and turned slightly inward toward the listener. Height speakers are a little trickier and must be elevated high on a wall facing downward or, ideally, within the ceiling. Often, an upward-firing solution like Dolby Atmos helps circumvent those kinds of tricky installations.