OK, I have been looking through your awesome site here for about 2 hours now. Car = I have a 2008 # 6 with Nav and JBL. I also added the Sirius radio. Aftermarket = I have a 12" Sub, ported box and a 600 watt amplifier that allows for high level input or RCA input. Here is what I know. Power - Fused line from 12V battery in trunk REM - Run from center console (only has power when car is on) Inputs - possiby cut into rear speakers (not sure on how get speaker wire or RCA cables from door to trunk) I have no clue where the JBL Amp is hiding, and Toyota has been zero help in locating it. (I told the dealer he should learn things like that. Not everyone just wants to save gas, you know.) There are two boxes under the seats. One under the driver seat, and one for the passenger side. Any guesses as to what these are? I appreciate any help. Once completed, I will show pictures and create a howto guide for you all.
They are not too hard to get at. you remove all the trim covers from the bottom of the door frame, and run the ries from there under the seat back into the trunk space. There is a post with photos on how to do it somewhere here, but cannot find it for the life of me.
Buried within the Audio forum is some excellent information and diagrams by others who have done the hard initial work. The "easiest way" is to unbolt the passenger seat and tilt it forward out of the way. Then you have easy access to the JBL amp whic you can also unbolt and work on that way. You need to cut wires between the three and wiring harness. After that the easiest thing to do is attach wiring bullet connectors (small gauge/red/Radio Shack) Then splicing or reconnecting back to original if needed is fairly easy. You have three connectors going in to the JBL - White - front-most for access to Front tweeters, Blue - middle connector front woofers and rear woofers. You probably want rear woofer wires ( Yellow (-) left; black (+) left) (Red (+) right; white (-) right). Also in the White rear-most connector you can tap into the gray wire for the 12 volt remote turn-on connection. I have the 2007 with JBL premium sound system and I believe the connections are the same for yours. rt
I don't use them, but some people have had success with Scotchlok signal taps. You can just clamp them over the speaker outputs coming out of the amp - no need to tap a signal in the door (no one with a clue would do that).