channels       1         2
             _________ _________ 
            | left    | right   |
  stereo    |         |         |
            |_________|_________|


                 1         2         3
             _________ _________ _________ 
            | left    | right   | center  |
  3 channel |         |         |         |
            |_________|_________|_________|

                 1         2         3         4
             _________ _________ _________ _________ 
            | front   | front   | rear    | rear    |
  quad      | left    | right   | left    | right   |
            |_________|_________|_________|_________|

                 1         2         3         4
             _________ _________ _________ _________ 
            | left    | center  | right   | surround|
  4 channel |         |         |         |         |
            |_________|_________|_________|_________|

                 1         2         3         4         5         6
             _________ _________ _________ _________ _________ _________
            | left    | left    | center  | right   | right   |surround |
  6 channel | center  |         |         | center  |         |         |
            |_________|_________|_________|_________|_________|_________|