Multichannel Formats
Overview of standard multichannel audio formats and their applications.
Naming Convention
The X.Y.Z format indicates:
- X: Main channels (ear level)
- Y: LFE/subwoofer channels
- Z: Height channels (Atmos/immersive)
Example: 7.1.4 = 7 main + 1 LFE + 4 height
Standard Configurations
Stereo (2.0)
The base of all reproduction:
- L (Left): -30°
- R (Right): +30°
5.1 Surround
Cinema and home theater standard:
| Channel | Position | Angle |
|---|---|---|
| L | Front Left | -30° |
| C | Center | 0° |
| R | Front Right | +30° |
| Ls | Surround Left | -110° |
| Rs | Surround Right | +110° |
| LFE | Subwoofer | - |
7.1 Surround
Adds lateral/rear channels:
| Channel | Position | Angle |
|---|---|---|
| L, C, R | Front | -30°, 0°, +30° |
| Lss | Side Left | -90° |
| Rss | Side Right | +90° |
| Lrs | Rear Left | -135° |
| Rrs | Rear Right | +135° |
| LFE | Subwoofer | - |
7.1.4 (Dolby Atmos)
7.1 + 4 height channels:
| Channel | Position |
|---|---|
| 7.1 | At ear level |
| Ltf | Top Front Left |
| Rtf | Top Front Right |
| Ltr | Top Rear Left |
| Rtr | Top Rear Right |
Channel Mapping Standards
ITU-R BS.775
International standard for 5.1:
L, R, C, LFE, Ls, Rs
SMPTE
Professional standard:
L, R, C, LFE, Ls, Rs (5.1)
L, R, C, LFE, Lss, Rss, Lrs, Rrs (7.1)
Film Standard
Cinema format (different from home):
L, C, R, Ls, Rs, LFE
Downmix
Converting from one format to a simpler one:
5.1 to Stereo
L' = L + 0.707×C + 0.707×Ls
R' = R + 0.707×C + 0.707×Rs
Downmix Verification
Always check compatibility:
- Mono (L+R sum)
- Stereo
- Target configuration
Ambisonic Formats
B-Format (1st Order)
Historical format, 4 channels: W, X, Y, Z
| Channel | Representation |
|---|---|
| W | Omnidirectional |
| X | Figure-8 front/back |
| Y | Figure-8 left/right |
| Z | Figure-8 up/down |
AmbiX
Normalized format (ACN + SN3D), most widely used today.
| Order | Channels | Resolution |
|---|---|---|
| 1 (FOA) | 4 | ~45° |
| 2 | 9 | ~30° |
| 3 (HOA) | 16 | ~22° |
| 4 | 25 | ~18° |
| 5 | 36 | ~15° |
FuMa vs AmbiX
| Aspect | FuMa | AmbiX |
|---|---|---|
| Channel order | WXYZ | WYZX (ACN) |
| Normalization | MaxN | SN3D |
| Usage | Legacy | Current standard |
Spacelite and Formats
Spacelite works with a flexible approach:
- Input: Stereo (2.0)
- Output: 1 to 16 channels per bus
- HSR: Distributes stereo across configured outputs
This allows adaptation to any format by adjusting:
- Number of active outputs
- Speaker positions
- HSR width and position parameters