I took a peak into the speaker wirings for my s4
and i found the passenger side speaker (australian model ie right hand drive) is bigger than the driver side.
Can anyone confirm this and give me the speaker sizes?

Also i took apart the rear speakers, and found a heat sink like thing. The speaker was connected in the normal +ve/ -ve way, but there was an extra connector with three wires? Possible amplifier for each speaker? Possible Split speaker system?

 

I can tell you this much. The stock audio system on the FC is a mess. The amps for the speakers are seperate from the deck. Heat sinks.... I seem to remeber those. Split speaker system.... Could be, mazda made the audio system way to complex for what is does. I don't recall the speakers being different sizes though.

 

Mazda seemed to like making a lot of things more complex on RX-7's as the years increased. First gens were pretty straightforward, second gens had a few things that made you scratch your head, and then you get to the 3rd gens and you think "what the hell was going on when they designed this thing"

Audio systems in Rx-7s are just one of the things.
Remove it all, put in your own stuff, good stuff with all your own wiring and fuses.