Subwoofer Install Help

So I know this isn't on my Tacoma but I'm hoping you guys can help me out. My brother has a 2015 Jeep Grand Cherokee with the factory upgraded 9 speaker alpine upgraded sound system that includes a factory amplifier and 8-inch Subwoofer. He bought a 12 inch Alpine Type S and a JL JX 500/1D amp from a buddy of his that he wanted to put into his car. I've only installed subwoofers into vehicles with aftermarket headunits so we went to our local car audio shop and bought the wiring kit and they recommended this PAC LocPRO Series. I found this diagram of the pins for the headunit and wired the PAC as follows: Front Right positive to wire from pin 46, front Right negative to pin 50, front left positive to pin 47, and front left negative to pin 51, and then grounded the PAC unit. The problem is when we turned the car on the subwoofer continues to play music if the JL RBC-1 dial is turned up even if the volume on the headunit is turned all the way down. Also when we do turn the volume up on the headunit the subwoofer gets quieter. My only thought is that the factory speakers are also wired into the factory amp and now that we tapped the wires for those speakers the factory amplifier is trying to power all the factory speakers, factory sub, and aftermarket sub, hence why the sub gets quiet when we turn the radio volume up due to the speakers pulling more power from the amp.

We tested the amp and the sub in my truck that already is wired for a subwoofer and both work great.

I'm not audio expert so I would love any assistance you guys could offer us and I will happily answer and questions.

 

Sounds like ANC microphones are kicking in and picking up the low frequencies from the new sub. Need to find a diagram, locate, and disconnect them.
ANC are designed to pick up low frequency noises and distort them from the human ear.

Also that LOC start with the gain turned down on the adjustable dial and work your way up until you start to hear distortion and then 1/8" turn back down and your set.

 

The issue you’re having is because it’s the Alpine system

The radio is sending an audio signal to the amplifier, and all of the volume control and EQ is done in the amplifier. So when you tapped into the wiring behind the radio, you are getting a full volume non-adjustable signal. You need to tap into the subwoofer outputs at the amplifier

or, the best possible option, is return that LOC and get this, made specifically to do what you want to do

https://www.crutchfield.com/S-C2Vgg...MIxYDt7529hQMVR6daBR0PIAWnEAAYASAAEgKlzfD_BwE

 

They definitely will not let us return the loc because weve already spliced it into the headunit, how much worse will it be to just tap into the outputs from the amp, quality wise. Also what do you think about the other posters reply?

 

Off the top of my head I don't know if that vehicle has ANC, but if it does, the ANC module will need to be disconnected because what he is describing will happen.

That AmpPro module is literally the perfect solution. Perfectly flat signal, unlike the factory sub output that is tuned specifically for that driver and enclosure and all that.
The loc you got is like $22 on Amazon so hopefully the shop didn't price gouge you too bad. I'd stick it in the garage for later.

 

Installed the kit you recommended, so much easier and I'll definitely look for those kits in the future. Thanks a ton!

 

Thats great to hear!
There are a lot of solutions like that and it's one of those things that you just dont know about until someone tells you about it.