Below is a passive surround converter/adapter circuit diagram. To make this circuit works, passive surround doesn’t required any active components. This circuit only need the combined of resistors and electrolytic capacitors. Do not use woofer or tweeter speakers for rear speakers but use full range type of speaker.
We must use 5W resistor. Usage of 1/4 or 1/2 watt resistor will make it burned. There are 4 speaker positions, LF : Output (connect to Left Front Speaker), RF : Output (connect to Right Front Speaker), LR : Output (connect to Left Rear Speaker), and RR : Output (connect to Right Rear Speaker). And there are three switch operations: quadraphonic, surround, and stereo (passive surround deactivated, Rear Speakers disconnected).