31 Oct Surround sound – What the numbers mean

Whether you are engrossed in the latest blockbuster movie, playing a competitive game of Rocket League with your mates, or watching the footy with friends, each speaker in a home entertainment system has a role to faithfully reproduce what is happening on the screen and around you.

When you’re first researching surround sound systems, you’ll likely notice many numbers with decimal points being thrown around, but what do they all mean? Enthusiasts and seasoned cinema designers may know, but let’s break it down for those just starting their journey into home theatre.

To put it simply:
First number = the number of speakers at the base (or ear) level – generally consisting of front speakers and surround speakers (which may be installed slightly higher if required).
Second number = the Low Frequency Effects (LFE) channel. There’s only ever one LFE track, but this number is commonly used to show how many subwoofers are in the system.
Third number = the number of height/overhead speakers, typically used for the new immersive formats.

5.1 – This layout consists of five speakers – the left, centre and right (all front speakers), with left surround and right surround speakers providing the ambience and surround effects. The .1 represents the number of subwoofers in the setup. In this instance there is a single subwoofer . A 5.2 layout is the same as a 5.1, but the .2 now represents two subwoofers in the system (both playing the same LFE track). There are no height/overhead speakers in this layout (as you may have guessed from the lack of a 3rd number).

Example 5.1 layout – Image is provided for demonstration purposes only. Layout of speakers will differ on personal circumstances including room size, furniture placement, products purchased and other factors.

7.1 – Similar to a 5.1 layout, 7.1 simply adds a second pair of rear surround speakers, generally behind the listening area. There are also no height/overhead speakers in this layout.

Adding an extra decimal.

With the release of immersive sound formats such as Dolby Atmos and DTS:X, movie sound mixers now have the opportunity to move sound above the listening area as well!

5.1.2 – This layout builds on the 5.1 setup above by adding height/overhead left and right speakers. You’ll notice the number of overhead speakers (2) is denoted as the third number in 5.1.2. These overhead speakers would generally be placed above and slightly in front of the listening area, however there’s a few different placement options available depending on your room and which AV receiver/processor you choose.

Example 5.1.2 layout – Image is provided for demonstration purposes only. Layout of speakers will differ on personal circumstances including room size, furniture placement, products purchased and other factors.

7.1.4 – This configuration is currently the sweet spot for immersive sound playback without breaking the bank… depending on what your definition of that may be! The layout is comprised of left, centre, right, left surround, right surround, left rear surround, right rear surround, left top front, right top front, left top rear and right top rear speakers.

Example 7.1.4 layout – Image is provided for demonstration purposes only. Layout of speakers will differ on personal circumstances including room size, furniture placement, products purchased and other factors.

The more speakers in a layout, the more positions for the sound effects to “anchor” to, creating even smoother “pans” and movement of sound as it makes its way around the environment. Think of a big V8 car that makes its way from left to right across the front soundstage and down the right side of the room before disappearing in the distance. The more speakers there are, the more precise the placement of the car and the more consistent it is for all viewers. With overhead speakers (especially four), the same movement and immersion can be achieved for helicopters, fighter jets and objects above.

We’ve just touched on a few of the layouts available – you could investigate a 5.1.4 or 7.1.2, even 9.1.6. Front wide speakers are becoming more popular and add a set of speakers between the fronts and surrounds, filling the (sometimes large) gap between the front speakers and viewers. At least you now have a better idea of what the numbers mean!

In a home environment, the Dolby Atmos specification allows up to a massive 24.1.10 layout! That’s 24 ear-level speakers and 10 overhead speakers. In 2018, Krix and Trinnov combined to present the world’s first presentation of a full specification 24.1.10 system.

Setups of 7.1.4 and above are generally used in dedicated home cinema rooms, but there’s nothing to say you can’t go higher in your multi-use media or lounge room.

Not all rooms can accommodate a large number of speakers – things like room size, seating locations, furniture, functionality, and other factors will all play a part in what’s best for you. Krix’s extensive dealer network will be able to answer questions, offer advice and start you on your own immersive audio journey!

For the ultimate sound experience at home, play it through Krix.