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Discussion Starter · #1 ·
Well, I was hoping that the ‘premium’ HK audio system would be good enough for me and I wouldn’t have to mess with it, but I probably knew all along that it wouldn’t be... So I decided to upgrade the subwoofer. One thing that I found to be a little odd is that I had a hard time finding info on the best way to do this. So here’s what I did. It was simple and I’m very happy with the results. Hopefully this makes it easier for someone else.

To get the RCA pre-out I used a PAC Audio AP4-CH41. It plugs into the CAN bus behind the touchscreen and gives the sub pre-out and remote turn on lead. It also has a gain potentiometer for sub volume, but I opted to use the one that came with my amp instead and mounted it in the USB port cubby. Leaving the AP4-CH41 gain pot disconnected is the same as having it connected and set at full output. Getting behind the touchscreen is very simple. The trim panel around it pulls off with something like 8 clips holding it in place, then there are 4 screws that hold the touchscreen down. Yes, I could have used something cheaper than the AP4-CH41 to get just a sub output, but for ease of installation and being sure I was getting a proper full range signal it was worth it to me. If you buy it from Crutchfield they will give you their install instructions, which are a handy reference that takes the guesswork out of how to get the various panels apart.

For the amp, I used an Infinity Kappa One K, which is the thinnest high output amplifier that I could find. I needed a thin amp because I opted to mount it on top of the battery, and with the passenger seat adjusted fully down there’s a bit less than an inch and a half to work with because of a metal bracket that holds a connector harness in place. If you removed that bracket you’d have a little more room available, but I didn’t want to mess with it. The amp is a bit over an inch and a half tall so if I were to put the seat all the way down the bracket would contact the amp, so I just leave the seat up slightly. Installing the amp there made the power wiring super easy and it’s virtually invisible unless you’re looking for it. I attached a couple pictures of the install from the back seat looking forward.

The sub box is from a place out of Jacksonville that will custom build it to the sub that you’d like to use. Here’s a link to their webpage:

Jeep Grand Cherokee Subwoofer Box | Made in the USA

Note that the cost of the box will depend on the sub that you want to use, and not every sub will fit – I wanted to use a 12” JL W7 but that was a no go. I recommend calling or emailing them to discuss what you’re looking for before you place an order. I ended up going with a 12” Memphis M6 instead, which is a great sounding sub. There are a couple pictures attached that show the new box vs the OEM box and what it looks like in the car. It was necessary to cut a little sheet metal to get it in there, and the rubber surround on the sub was too tall so I also had to modify the trim panel to get that to clear. But it was worth it to me for big bass without losing the spare tire or any storage space.

The ANC mics also very likely need to be disabled. I just killed them from the start and didn’t bother doing any before and after testing. The mics can be disabled by clipping 4 wires at the factory HK ‘amp’, which is located on the rear driver’s side quarter panel. Once you take out the spare tire trim it’s 100% accessible. I’ve attached a diagram of the wires to clip to accomplish this.

So the verdict? Bass is night and day better, and the sub hits surprisingly hard especially considering it’s in a small sealed box. The OEM system (other than the weak sub) actually sounds pretty damn good to me, so I really didn’t see any need to mess with it. Now that the low end is there, I’m happy.
 

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Very well done sir. Could you have tapped the PAC unit wires at the factory amp to prevent removing the touch screen?
 

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Discussion Starter · #3 ·
One of the benefits of the PAC unit is it comes with a harness that makes it completely plug and play, no splicing required. But the harness only works with the plug behind the touchscreen. I was a little apprehensive about pulling the trim off and removing the screen but it really couldn’t be simpler. Just open the door to the USB cubby area then tug on the bottom of the trim ring. The clips release pretty easily and it comes right out. I had to get back there anyway to mount the sub volume control behind the cubby door so putting the PAC unit in there didn’t really create any extra work.
 

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Discussion Starter · #5 ·
Yes, definitely considered a JL stealthbox. It houses a 10” W3 sub, which is still a huge upgrade over what’s there from the factory. However, for my listening style it’s almost impossible to have too much sub, so the 12” M6 was a good compromise for what can fit in the OEM location without losing the spare tire. Plus, the install effort is basically the same, so why not go bigger?
 

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Discussion Starter · #7 ·
The PAC unit is great. It's compact, completely plug and play and just does what it's supposed to do with no drama. Plus the support guys over at PAC are pretty awesome - they're the ones who gave me the info on how to disable the ANC mics when I asked if they had a solution.
 

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Discussion Starter · #9 ·
They do have a ANC disable harness, but it’s only for the non-amplified head units. If you have an upgraded HK system no harness exists, so it’s necessary to clip the wires at the amp in the back. Definitely cheap and easy, but I still would have rather bought a harness to avoid that “I hope these are the right wires” moment 😂
 

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Discussion Starter · #11 ·
Yes, I believe if you don't have the HK amp in the back then PAC's ANC disable harness should work for you. Submit a question on their webpage to confirm, they're very good about responding.

As far as the weight of the box goes, yes it is definitely heavier than the plastic 'sub' that came out. The inside of the box is actually coated in fiberglass to give it additional strength, but I don't think they have the capability to build the box completely out of fiberglass. I didn't weight it, but as someone pointed out in another thread, Trackhawks are basically giant heavy bricks so another 20 or 30 pounds in the back isn't really going to matter much. I suppose if you wanted to be picky about it, the weight is sprung and located directly above the tire that's most likely to spin, so maybe there's a benefit ;)
 

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So, how does an audio upgrade mess with the ANS? I’ve used thot PAC unit on my Ram and Hellcat and it allows you to bypass everything. So I’m confused as to what happens when the ANS is not disabled and if “drone” is not allowed into the cabin.

forgot to mention I have the base Alpine system (if it matters). The HK was ok in the H*llcat but I changed it out to Hertz ASAP and already have Focal waiting to throw in the TH.
 

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So, how does an audio upgrade mess with the ANS? I’ve used thot PAC unit on my Ram and Hellcat and it allows you to bypass everything. So I’m confused as to what happens when the ANS is not disabled and if “drone” is not allowed into the cabin.

forgot to mention I have the base Alpine system (if it matters). The HK was ok in the H*llcat but I changed it out to Hertz ASAP and already have Focal waiting to throw in the TH.
The ANC system uses the sub to play some of the frequencies to cancel the noise. When you add an aftermarket amp/sub, it can cause boominess.
 
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