Mix 51 is made up of two main components. First, there are Mono and Stereo Panner plugins that can be placed on track inserts to pan, mix and route audio to the Mix 51 Surround Mixer buses. Second, the Mix 51 Surround Mixer plugin provides 30 channels of outputs, grouped as three 5.1 main buses and three quad auxiliary buses. Surround Mixer is an RTAS plugin which can be placed on any mono or stereo track. A single instance of this plugin manages all Mix 51 surround inputs and outputs in a Pro Tools Session, so it is not necessary to have more than one Surround Mixer in any one Session. Because its inputs come from Surround Panner plugins and its outputs appear as Pro Tools track inputs, it is not critical where you place the Surround Mixer plugin, as it does not process any audio on the track where it is located. The audio is simply passed through from input to output.
The mixer is fairly selfexplanatory, and gives you metering plus volume, solo and mute controls for each of the three 5.1 mix buses and quad auxiliary buses. The Surround Panner plugin operates as an RTAS plugin on mono and stereo tracks. It will simultaneously pan to one of the 5.1 main buses and to one of the quad effects send buses, and provides panning, volume, mute, solo, LFE and divergence controls. By default, the Mix 51 Panner does not output any audio to the normal Pro Tools mixer, but hitting the Bypass button will pass the signal to the Pro Tools mixer as well, so you can set up an additional stereo mix while also continuing normal Mix 51 operation.
It is even possible to have multiple panners on a single track, so you could route a track to two different Mix 51 main or send buses.