I know just enough electronics to get myself into trouble and I am currently very confused by the wiring of the speakers in MMr: Wiring speakers in series or in parallel is only a consideration when you have the same audio coming out of both speakers. The audio chip used (if it is in fact a TPA3116) is a 2 channel amp and is designed to power 2 speakers (each 4ohms or greater). So I would have thought you could just pop in lower impedance speakers no problem. But the wiring diagram looks like something very strange is happening as it uses 3 wires to connect to the 2 speakers. Is a stock machine using one channel for a sub and the other channel to drive the 2 backbox speakers?

EDIT: I just looked at the schematic more and that is what's going on. One channel for the sub, the other channel is wired in parallel to the 2 speakers. This makes sense now that if you replace with 4ohm speakers, switch to series wiring. I think someone previously mentioned that doing this mod loses stereo sound, but that's not the case. It's mono already.

Correct in that it's the same audio coming from both speakers in the backbox.
There are 2 audio channels, but one of the channels goes to the subwoofer.

EDIT: The sound coming from the two speakers is actually slightly different because one of the speakers has a capacitor connected in series (On the original MM, that speaker was a tweeter and I believe the cap is to filter out the low end).

Come on man, just 8 posts ago, nosro put up great instructions and even labeled it "In case anyone needs a 'for dummies' version, here's a wiring diagram"

For anyone interested, it looks like those Kicker speakers are on sale at BestBuy right now for $30 with free shipping:

http://www.bestbuy.com/site/kicker-5-1-4-coaxial-car-speakers-with-polypropylene-cones-pair-black/7709184.p?skuId=7709184

I think the biggest reason is cost. I picked up those Kicker speakers for $30 including shipping and the Flipper Fidelity are over $65 ($20.81 is the cheapest shipping option to CA, ouch).

They're probably about comparable in quality