JVC 8 pin pinout - speaker cable
Looking at the connector, there are 3 rows of pins.
Starting with the first row closest to the alignment mark:
[Power On],[Center Speaker],[Sub Woofer]
[Surround Right],[Speaker Ground],[Surround Left]
If you are trying to connect two JVC units, you will need an 8-pin cable that has the SAME pins connected on each side. You will need to test this using a multimeter set to ohms or 'connectivity'.
There are other 8-pin cables out there like the one for apple networking, but they use a crossover pinout where pin 1 on one end = pin 3 on the other end. This is bad. JVC needs pin 1 to = pin 1.
This is a standard connector/pinout setup that JVC uses, so connecting a TH-C3 to a TH-C50 works fine. There is a bunch of intermixing that you can get away with. The only thing to keep an eye on is the power in watts that one unit sends and the other recieves. Worst case is that the speakers are quiter than expected or that you can turn the volume up so high that it can damage the speakers. In all cases, you should get desired volume somewhere on the dial.
If you are trying to wire the speaker set custom, then you will need to take note that an '8-pin' connector is actually a 9-wire connector. Along with the above pinout, you will need to add Case Ground, which is the metal circle that surrounds the pins. To make the speakers turn on, you will need to apply 12v to the Power On pin and ground the 12v source to the Case Ground outer ring.
The system takes 3 to 4 seconds to fully turn on after this connection is made. Speakers should be wired using the center pin for speaker ground and each other pin respectful to each speaker.