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What is surround sound? 5.1, 7.1: What are these numbers?

Getting more from your home theater requires a deep understanding of the importance of sound when watching a movie.

While it’s true that internal TV speakers and affordable soundbars can deliver satisfying results, they simply can’t replicate the cinematic experience most of us look for.

A cinema-like sense of realism and immersive effect can only be brought to life with an audio system that can recreate the way sound travels in real life, and in order to achieve that, you need to have a surround system that’ll fit in your room and meet your budget.

surround sound guide

Starting to create a surround system for your home theater is relatively easy and requires understanding only a few basic concepts, like speakers’ placement, how channels are defined, and the difference between Dolby Digital, Dolby Atmos, and DTS.

In this article, I’ll explain in detail what surround sound is and how it can enhance your movie-watching experience, the differences between different configurations, and how you can make the most of your upgraded sound system.

About the author

I’ve worked in music and sound design for over a decade, and over time I developed an interest in audio technologies for home theaters. I’ve had the chance to collaborate with many companies developing ground-breaking audio technologies, which means I know what the best surround systems in the market these days can deliver to viewers.

What is surround sound?

Surround sound in movie theaters replicates the way we experience audio in real life by placing speakers in all directions and having them reproduce certain sounds to immerse the listener in a realistic soundscape.

In a surround sound system, each channel is dedicated to specific sounds: the central channel to dialogue, the left and right channels to the soundtrack and sound effects, and the subwoofer to lower frequencies.

To achieve a cinematic experience, sounds should come from where the sound source is in the movie: a car coming from the left side should be heard from that side, a gunshot from the right side, and so on.

Internal TV speakers and soundbars can create a limited sound spatiality, but if you want to get optimal results, you’ll need to have dedicated speakers for each channel and place them where the sound should come from.


What you need to create a surround sound system at home are speakers, a receiver, and a subwoofer.

You can start building your surround sound with a basic stereo setup: two speakers placed on each side of your TV, powered by a receiver. This will upgrade your home theater’s audio quality, but you won’t feel immersed in sound.

A receiver is a device that connects multiple speakers to your TV or playback device. It’s a crucial tool when creating a surround sound system, as it connects all your speakers to the audio source.

A subwoofer reproduces the lower frequencies that speakers cannot reproduce faithfully: it’s a great addition to a surround sound system, especially if you want to emphasise the energy of low-frequency sounds, like explosions or heavy-bass music.

Numbers (configurations)

If you started doing some research on building your surround system, you probably came across numbers like 2.1, 5.1, 7.1, 9.1, and more.

Understanding these numbers and what they mean is crucial if you want to understand how surround systems work and find the best solution for your home theater.

The first number in the sequence refers to the number of speakers, for example, a 2.1 system is a surround system with two speakers, one on the left and one on the right.

The second number is the number of subwoofers: you can have one, two, or even more if your home theater requires it.

In my experience, one subwoofer is enough to meet the demands of most home theaters, but if you feel lower frequencies are overshadowed, you can always place one on the opposite side of the room for an enveloping bass effect.

What is 5.1 audio?

5.1 is a standard configuration and requires five speakers: left, right, centre, left rear surround, right rear surround, and one subwoofer.

5.1 and 7.1 speaker configuration

This is an excellent option for people who want to enhance the audio experience of their home theater without the hassles of an overcomplicated setup.

What is 7.1 audio?

7.1 is similar to the 5.1 configuration, with the addition of two extra speakers placed on the viewer’s sides.

In this way, you’ll have four speakers dedicated to surround effects instead of two, further enhancing the spatial dimension provided by your surround system.

You can create a sense of altitude by adding two more speakers on top of your left and right front speakers, this is called a 9.1 configuration, which adds a new dimension to the sound and makes it much more immersive compared to other configurations.

What does the third number mean?

You might see a third number in the speakers’ configuration, like 7.1.2 or 9.1.2. The final number refers to the in-ceiling or upward-firing speakers, both of which can give you the sense of sound coming from above.

The in-ceiling speakers are placed inside the roof of your room dedicated to home theater, whereas upward-firing speakers are standing, directing the audio to the ceiling, which bounces back and reaches the viewer’s ears.

This is undoubtedly the best way to achieve the realistic sonic experience of cinemas.

The technology

It’s essential to understand how audio systems decode and interpret sounds coming from media sources.

Let’s take a look at the most common surround sound technologies used in physical formats like DVDs and Blu-Rays, as well as streaming platforms.

Dolby Digital

Dolby Digital is the original encoding technology that allowed a multi-channel audio experience.

Originally developed in the early 90s for theaters, it’s still considered an industry standard for home theaters as it converts an audio signal into an efficient 5.1-channel, 16-bit/48 kHz format at 640 kbit/s.

Dolby Atmos

The evolution of Dolby Digital, Atmos upgrades the sense of spatiality by incorporating height channels, giving three-dimensionality to audio objects which can come at you from all directions.

This technological revolution allows an immersive, 360-degree audio experience in home theaters.


DTS (Digital Theater Systems) is Dolby’s main rival and offers audio quality comparable to its most popular counterpart. DTS-supported devices include the Xbox Series S and X, as well as many TVs and soundbars.

Most top AV receivers work with both technologies, so most likely, you won’t have to worry about compatibility. DTS:X challenges the Dolby Atmos technology with a similar audio three-dimensionality but without the need for height speakers.

It’s hard to compare these two cutting-edge technologies, but I’d say that despite DTS’s higher bit rate, Dolby technology is most widely supported by home theater applications and cinemas, so if you have to choose, go for Dolby Atmos.

Final thoughts

I hope this guide helped you clarify the most crucial aspects to consider when creating a surround system.

I recommend starting small, ensuring you’re buying audio gear that’s easy to upgrade, and gradually investing in better equipment as your desire for sonic clarity increases.

Options for good-quality surround systems are endless out there, so take your time to analyse your requirements and budget before investing in something you might not need.

Good luck!