Multi-Channel Audio By The Numbers

April 2, 2019

2.0, 5.1, 7.1.4…

What do all of these numbers mean and how do I know what to look for when designing an audio system for my home? These numbers make up a code for different types of home audio systems and we’re here to break that code.

To begin, we need to know that these numbers represent how many audio “channels” are in a system. An audio channel can be looked at as a lane on a road or highway and the vehicles on that lane can represent sound. We can have a one-lane road or a multilane superhighway.

1.0 Mono – The One Lane Road

The first known audio recordings were made in the mid-1850s. These recordings captured the human voice and, eventually, other sounds on a single channel. Since there was only one channel of audio, these recordings came to be known as “mono.” To reproduce these recordings, only a single speaker is required. A mono recording can be played back on the system with more than one speaker, but each one will play the exact same audio content.

2.0 Stereo – The Two-Lane Road

The first experiments in recording two channels of audio began in the late 1800s. Capturing sound from left and right horizontal positions with two microphones presented the ability to position the sounds being recorded across a horizontal plane. When the system is played back, two speakers are positioned in front of the listener on both the right and left sides. As a result, the reproduced performance could have a similar feel of space and position with respect to the original performance. This reproduction in two channels became known as “stereo.” Most music recordings to this day are captured in stereo.

Fun fact: The word “ stereo” comes from the Greek word “stereos” meaning “solid”.

Fun fact: The first commercially released movie with a stereo soundtrack was Walt Disney’s “Fantasia” in 1940.

3.0 – Adding a Center Channel

As stereo recordings grew in popularity, system designers began to add a third front speaker. This speaker is found located directly in front of the listener and precisely between the left and right channels. This speaker became known as a “center channel.” The center channel’s job was to help locate audio (especially dialogue) coming directly from the action on the screen. The center channel has become more and more critical to the proper design of a home entertainment system and accounts for a considerable percentage of dialogue for most TV shows and movies.

4.0 – Quadraphonic

This approach was comprised of four audio channels sent to four speakers positioned at the corners of the listing environment. Multiple recordings in and around the 1970s utilized this format but due to technical difficulties and the expensive price point of the components, audio was relatively short-lived.

Drop the Bass – the “Dot 1” (.1)

So now we are getting to know what the first number in a home entertainment speaker system description means (2.0, 3.0, etc.). What about the “.1”? When you see a “.1” after the first number (such as 3.1) it means the system has a subwoofer speaker. The subwoofer doesn’t get an entire whole number because it doesn’t play the entire range of sounds. It focuses on the very low sounds that are very difficult for the other speakers in the system to reproduce. The sub woofer’s job is to fill in the lowest sounds in the audio recording. It does this by either gathering the lowest content from the other channels or relying on a separate channel used by the producer, specifically for the subwoofer.

Subwoofers are extremely important to most home entertainment experiences and bring life and energy to the music, along with special-effects in the soundtrack.

5.1 and 7.1 – We Are Surrounded

When five speakers plus a subwoofer are used in a system to surround a listener, there are three speakers in front (left, right and center), two speakers behind the listener and a single subwoofer (5.1). In the late 1900s, “surround sound” channels began to be included in stereo recordings and encoded for cinema audio systems using an encoding method called Dolby Stereo sound. Despite its name, this included a center channel as well as a surround channel sent to speakers positioned behind the listener. This creates a more immersive entertainment experience. These channels gave audio producers the ability to place sounds around the listener and add a greater element of reality to movie soundtracks. The home version of this technology was called Dolby Surround, but it ultimately evolved into Dolby Pro Logic. In the early 1990s, Dolby developed a digital surround sound compression method for cinemas called Dolby Stereo Digital, which eventually became known simply as Dolby Digital. The Dolby Digital system carried more than just two-channel “stereo” information as its home version became known as Dolby AC-3.

Fun Fact: The first movie soundtrack encoded in Dolby Stereo to include Left, Right, Center and Surround information was “A Star Is Born” in 1976.

Fun Fact: The first movie soundtrack encoded in Dolby Digital was “Batman Returns” in 1992.

If five is good, seven must be better. When seven speakers were used, an additional two speakers are placed to the left and right sides of the listener. This ultimately created greater sound positioning capabilities (7.1). In 2010, Dolby introduced Dolby Surround 7.1. In a 5.1 system, the “surround” information is all sent to the two speakers positioned behind the listener. This information is separated to the left and right speakers, but it is all located behind the listener due to the physical locations of the speakers. The 7.1 format adds two “side” speakers and allows sound to be localized to the left and right sides as well as the left and right rears of the listener. This provides do a better “surrounding” to the listener in an immersive audio experience.

Fun Fact: The first movie soundtrack encoded in Dolby Surround 7.1 was Pixar’s “Toy Story 3” in 2010.

Moving Up – The Number After the Second Dot

We started with a single channel (1.0), grew horizontally to create stereo (2.0), added a center channel, and surrounded the subwoofer (5.1 and 7.1). Now, with the latest innovations in audio, we can grow upward. The number after the second dot defines the number of “ elevation” channels in a system. The elevation or height channels were introduced by Dolby in 2012 and called Dolby Atmos.

While in professional cinemas there can be a large number of elevation channels, the home environment typically utilizes either two or four such channels. The first two are located in the front of the listener above the left and right channels. Some systems position the speakers playing these channels on or in the ceiling while other systems utilize “up firing” speakers that physically sit on top of the left and right channels. The “bounce” sounds off of the ceiling making them appear to the listener as if they originated above them (3.1.2, 5.1.2, etc.). Similar to systems with four elevation channels, speakers are also positioned above the two speakers located behind the listener (5.1.4, 7.1.4, etc.).

Content with elevation channels is becoming more and more popular. You’ll often hear this high-quality audio in movies and television programs. It ultimately increases the listeners’ immersion within the sonic environment.

Fun Fact: The first movie soundtrack encoded in Dolby Atmos was “Brave” in 2014.

Fun Fact: The first TV show soundtrack encoded in Dolby Atmos was “Game of Thrones.”

Your System

The world of audio is constantly evolving, and significant engineering and content production continue to make our entertainment experiences better and better. Whether you were designing a 2.0 system to enjoy your favorite music or a 7.1.4 fully-immersive home entertainment experience, it is now possible to easily bring all of these amazing experiences into our homes.

In fact, that’s WiSA’s mission. The WiSA team is comprised of more than 60 global members, which makes immersive, multi-channel audio easy to set up. You’ll be able to enjoy the defined sound quality because of worldwide standards that allow companies to develop TVs, gaming systems, AVRs, speakers, computers and more that work seamlessly together.

This interoperability of great gear from leading brands allows people all over the world to simply and easily create amazing home entertainment systems and enjoy their favorite TV, movies, music, and games more than ever before.

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