SU-27 Surround Matrix Decoder

A matrix decoder attempts to extract multiple audio channels from a stereo pair. This extra channel content can be placed in the matrix by a purposeful encoding process, or as a byproduct of effects such as reverb. The SU-27 takes a stereo input, and processes it to create 3, 4, or 5 channels of output.

The additional channels created by the SU-27 can either be directly wired to the hardware output jacks in Reason, for use with multi-channel audio interfaces. Or exported to disk a series of mono or stereo tracks to be combined together with one of several freely available utilities.

On the face of the SU-27 there are four controls to help you fine tune the output.

• Center Spread - Takes the content that would normally be sent to the Center output, and divides it equally between the Left and Right outputs.
• Surround/Front Fader - Adjusts the surround (Left/Right Surround) vs. front (Left/Right/Center) levels by ±3 dB.
• Stereo Wrap - Instead of using the decoded surround information, the Left and Right output audio is copied to the Surround channels (Fader and Phase can still be applied).
• Surround Phase - The default decoding usually results in the Right Surround channel having an inverted phase from the Left Surround. This is desirable in a multi-channel playback system, as it creates a phantom effect. But it may not be as desired if the Surround channel audio is to be recombined for a different effect. The phase or either, or both Surround channels can be inverted independently.

On the rear of the SU-27 there are the usual two input jacks (Left and Right), and five outputs (Left, Right, Center, Left Surround, and Right Surround). The outputs are labeled with their intended targets, but other uses are possible for creative effects.

Most combinations of inputs and outputs are recognized. There is a diagram next to the output jacks that will change to indicate the mode in which the SU-27 is currently operating. While it is possible to connect a mono input, it’s not possible to do any decoding with a single signal. The output modes with a mono input are limited to simply passing the audio through (if the Center output is connected it is preferred for mono content).

The SU-27 does not support loading patches directly, but there are a few examples of standard uses included. Browse the Rack Extensions section for the SU-27 Surround Matrix Decoder file folder for a selection of Combinators and Song Templates.