We need to stop thinking of matrix as just a way of cramming 4 discrete channels into a 2-channel medium. Each matrix system is a continuum of pan positions. The 4 channels are the encodings that pan to where the speakers are.
But there are other pan positions in between. Depending on the system, those pannings show up in multiple speakers. And if you really want, a speaker can be put in to respond to any of the pannings.
I did this in my first year of experimenting with quad. In the process, I realized that the Scheiber system, the Hafler diamond, the EV system, the QS system, and Dynaquad are all variations in the same continuum. I built an 8-channel system using both the QS and Hafler diamond decodings. They work very well together. Each speaker is perfectly decoded for the location of the sound in the other system.
Here is a diagram of the continuum. Ignore the numbers (part of another article).
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From this I then devised a simple encoding system using a standard 4-bus mixer and a special encoding module I put in bus inserts 3 and 4. The resulting encodings work equally well in any of these systems (and SM too).
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The continuum aspect lets me put the sound anywhere in a circle around the listener with only two controls per mixer channel strip:
- The pan control pans the sound to any position around either the front half of the circle surrounding the listener or the back half.
- The bus selectors choose whether the sound is panned in either the front half or the back half of the listening area.
Select buses 1 & 2 for front, and 3 & 4 for back.
For mixers with pan controls on each bus, buses 1 and 3 are panned left, while buses 2 and 4 are panned right.
Feed the output of the mixer into a matrix decoder to monitor the mix.