The LFE Routing tab is the first of two matrix mixers. This mixer has 9 inputs: the eight speaker channels (optionally high pass filtered) and the output from the LFE Mgmt tab.
Each input to the mixer can be routed to any of the mixer outputs. Each input (down the left) can be routed to more than one output (along the top). If more than one input is routed to a given output, they are summed together.
To illustrate the routing example, we will use the signal flow diagram overlaid with blue to indicate where signal flows for that particular example. The diagram below shows the "straight through" routing. This is the default routing set by the matrix shown above.
The diagram below shows the signal flow for bass management, simplified to show only the front left and right speaker channels:
- The LFE Mgmt block creates an extra signal that contains the low frequencies from the speaker channels, summed with the LFE input channel.
- The LFE Routing block must route this signal to the subwoofer. Assuming the subwoofer is connected to channel 3, the matrix is as shown below.
Upmixing refers to routing a channel to more than one output channel. The figure below shows the signal flow for a simple case of upmixing. In the case where you have 7 speaker channels but the source material only has five channels, the surround channels can be upmixed to the rear channels:
This is the matrix for this example:
Note that upmixing should be done in the first mixer, LFE Routing, and not in the second mixer, Matrix Mixer.
Downmixing refers to mixing more than one input channel to a single output channel.
The figure below shows the routing matrix for a simple case of downmixing. In the case where you have only 5 speaker channels but the source material has seven channels, the rear surround channels can be downmixed to the side surrounds:
Note that downmixing should be done in the first mixer, LFE Routing, and not in the second mixer, Matrix Mixer.