Hey David! Any luck with your install? .. I am almost done with mine hoping to finish it up this weekend and see how it turns out! I will keep you posted the wiring diagram from the other post was huge!!! It should save me some time once i get it all opened up
Sorry for the late reply AlphaLame.
GM made this a nightmare by adding the chimes/blinkers to the factory audio system. Hopefully they release a software fix in the future? Until someone figures out how to quiet up the amplified chimes/blinkers here is where I ended up.
I separated my system from the factory head unit. This appeared to be the only way to get rid of the amplified chimes/blinkers. This system hits "EXTREMELY HARD" but does not cause any battery issues or "flickering" of lights and no sound clipping or cutout.
As of now here is my system config (with thumbnail photos):
1-Audio Control Three.2 EQ tucked in front above the wireless charging pad (used to control all volume & combined bass control)
2-separate black bass control knobs tucked under the armrest (controls each set of subwoofers interdependently)
My Phone plugs directly into EQ via USB-C or Lighning with instant connection to music (could have been Bluetooth but I did not want any lag and connection issues)
The EQ feeds all 4 JL Audio digital amps (front/rear/subs ~ all tucked under the rears seats)
1-JL Audio Xd400/4v2 amp feeds 4 factory Bose speakers in doors (front/rear)
1-JL Audio Xd1000/1v2 amp feeds 2-JL Audio 12tw3 subwoofers (shared box space closest to the lift-gate)
2-JL Audio Xd600/1v2 amps feed 2-JL Audio 12w6v3 subwoofers (independent box space just behind rear seats)
The factory head unit feeds the factory Bose center speaker only (on top of dash) for all chimes/blinkers and radio stations (not the best but the loud chimes drove me crazy)
. The stereo shop said they still need to swap the factory feed from the left front drivers door speaker with the center speaker feed so that the factory Bluetooth/OnStar "Mic" will work properly. Supposedly they just ran out of time but I am hesitant to believe it. I think they tried this and it failed but they did not want to admit it?
I will update when I do this.
My subwoofers use the space where the spare tire/storage was housed (yes I'll need a tow if I get a flat). You'll notice I removed the aluminum guide rails and the factory lift-up tire/storage cover for a clean look.
I also have an elevated platform/cover (not in photos yet) that is being carpeted and will have LED lighting that covers the woofers and allows for full storage space in the back. It will have the blackout "BLAZER" emblem (used on the outside of the drivers/passenger doors) visible on the edge when you open the lift-gate and will have the "JL" Audio logo lighted up through the carpet where each subwoofer is underneath.
If anyone wants a shop local to them to cut this box with a CNC router I might be able to send them the file??? It just glues & screws together, then you seal the inside with silicone and carpet it. Pretty easy for a novice to do.