Multichannel sound

Here is a document on the different mono and multichannel broadcasting formats. Since there are a large number of them, many of which have been abandoned, we will focus on the main ones.

Happy reading!

Introduction

Multichannel sound allows for two quite distinct things:

• Reproducing a sound recording recorded in stereo or multichannel. Example: a multichannel recording of a forest ambiance will allow the listener to pinpoint where a particular bird was located in the space.
• Creating this sense of immersion from scratch. Example: a film's sound mixer can make a spaceship move from the rear left to the front left, passing by the left side.

It is important to know that these formats are mostly intended for the world of cinema. Indeed, this implies the idea that a screen requires the listener to be fixed, facing it.

Naming

You will quickly see that I will express their names with a "dot" number. The first number indicates how many speaker channels (or satellites) there are, and the second indicates how many subwoofer channels (or "LFE", for Low-Frequency Effects) there are. For example, in "7.1", it is a system with 7 speakers around the listener + 1 subwoofer.

This does not prevent an installer from:

• Adding multiple speakers to increase power: for example, 2 subwoofers for a 7.1 system, but both will be connected to the same single channel.
• Adding multiple speakers to increase quality: for example, a speaker for high frequencies and another for mid frequencies, on the same single channel.

Types

We distinguish different types of sound broadcasting:

• Monophonic: which is not multichannel since there is only one channel.
• Stereophonic: which is the first multichannel as it has two channels.
• Surround: which has several channels, at the front and back of the listener, but on a single horizontal plane. It is said to be a 2D (two-dimensional) system.
• Ambisonic or Immersive: which has multiple channels on several planes, usually 2 to 3 levels (low, mid, high). It is said to be a 3D (three-dimensional) system.

In Detail

1.0 - Monophony

Used in the field of music until the advent of stereophonic recording (in 1958), monophony is still widely used in telephony and children's toys.

The principle is to broadcast a single channel on one or more speakers.

2.0 - Stereophony

Popularized with the first commercial release of the first stereophonic record in 1955.

The principle is to simultaneously broadcast two channels:

1. Channel 1 on the left speaker
2. Channel 2 on the right speaker.

2.1

With the introduction of the ".1", the subwoofer makes its entrance.

Be careful not to confuse it with a stereo system that would broadcast a mix of both speakers (left and right) to a subwoofer. Here, it is a true additional channel, intended only for the subwoofer. The audio file thus has a third channel.

The principle is to simultaneously broadcast three channels:

1. Channel 1 on the left speaker
2. Channel 2 on the right speaker
3. Channel 3 on a subwoofer.

4.0 - Quadraphonic

Mainly used in music from the 1970s, it is the first truly multichannel format. It offers channels 1 and 2 at the front and channels 3 and 4 for two speakers placed behind the listener.

The principle is to simultaneously broadcast four channels:

1. Channel 1 on the front left speaker
2. Channel 2 on the front right speaker
3. Channel 3 on the rear left speaker
4. Channel 4 on the rear right speaker.

4.1

This format offers 3 front channels, a left, a right, and a center, one channel behind the listener + 1 subwoofer.

The principle is to simultaneously broadcast five channels:

1. Channel 1 on the front left speaker
2. Channel 2 on the front right speaker
3. Channel 3 on the front center speaker
4. Channel 4 on a subwoofer
5. Channel 5 on the rear center speaker.

5.1

This format offers 3 front channels, a left, a right, and a center, two channels behind the listener + 1 subwoofer.

The principle is to simultaneously broadcast six channels:

1. Channel 1 on the front left speaker
2. Channel 2 on the front right speaker
3. Channel 3 on the front center speaker
4. Channel 4 on a subwoofer
5. Channel 5 on the "surround" rear left speaker
6. Channel 6 on the "surround" rear right speaker.

6.1

Like a 5.1, but with the addition of a surround speaker behind the listener. This format, rarely used, was developed in 1999 for Star Wars Episode I - The Phantom Menace.

7.1 - Dolby Surround

This format offers two front channels, a left, a right, and a center, two side channels, two channels behind the listener, a left and a right + 1 subwoofer.

In 2010, Toy Story 3 was the first film released in 7.1.

The principle is to simultaneously broadcast eight channels:

1. Channel 1 on the front left speaker
2. Channel 2 on the front right speaker
3. Channel 3 on the front center speaker
4. Channel 4 on a subwoofer
5. Channel 5 on the "surround" side left speaker
6. Channel 6 on the "surround" side right speaker
7. Channel 7 on the "surround" rear left speaker
8. Channel 8 on the "surround" rear right speaker.

It should be noted that this format then has 10 channels: 7+1 + 2 additional channels: the ninth is intended to be connected to a headset, with simplified audio, in mono and providing enhanced sound for hearing-impaired people, the tenth channel is intended for audio description in mono mainly for blind or visually impaired people. Personally, I often use audio description to "watch" a movie while working on something else.

10.2

This is when we start talking about immersive sound: meaning it provides height information with 4 speakers placed at height.

The principle is to simultaneously broadcast twelve channels. Which I do not have the motivation to detail :D

22.2

Immersive sound is reinforced in height and a new level of speakers is placed on the ground. A second channel for the subwoofer is added.

The principle is to simultaneously broadcast 24 channels. Which I do not have the motivation to detail :D

♥ - Joseph SARDIN - Founder of BigSoundBank.com - About - Contact