I thought I'd share my experience of upgrading the 8" sub in my 2018 RDX advance. After doing some research here on the forums, I decided to upgrade the existing 8" sub and added an amplifier to get some better boost. The sub upgrade by itself did not do very much, if anything. After additional amplification, it's like an entirely new system. The items I added were a Kicker 48CWRT84 CompRT Series shallow-mount 8" subwoofer with dual 4-ohm voice coils (300w RMS / 600 Pk) (Crutchfield) and an existing Rockford Fosgate R250X1 (verified at 315 W RMS) from a previous install. This pair matches really well together with the RF amp using the high level inputs from the existing sub wires.

Below is a picture of the cover removed from the driver's side of the center console.

Driver side existing radio amplifier under center console


In order to power up the amplifier you have to find a way through the firewall. I found the easiest way through was from the passenger side footwell. Remove the plastic trim that covers the fan below the radio and that will give you access to the grommet located in the passenger footwell shown below.

Grommet in passenger footwell - through firewall


Grommet through firewall in passenger footwell


Grommet through firewall in engine bay


The grommet is pretty stout. You will need something sharp to create a hole though. Be careful not to puncture any existing wires (bad news will ensue). I used a very sharp fillet knife to puncture a hole to the left side of the grommet. Once you have a hole through, you can fish the wire from the passenger side through the firewall into the engine compartment. I used 8ga welding cable (I find it works great for car amplifier installs) - very flexible and very durable. I zip tied it to the existing harness all the way to the battery. Make sure you use good practice and fuse right at the battery. Finally to finish off, I used Permatex The Right Stuff to seal both the engine bay and passenger side grommet wire. This is very good sealant and holds up to extreme temps well.

Through the firewall


You will also want to remove the ANC plug under the center console as shown in the picture below. Otherwise you get some bad feedback as the system is very overdamped when starting. It does settle out after about 20-30 seconds, but was too annoying to me to keep the ANC. I don't notice any additional cabin noise without it.
Remove ANC plug - under center console driver's side


Below is a picture of the sub mounted in the existing enclosure. I added a bit of polyfill to make add a bit of dimension to the existing enclosure. And, contrary to what is posted, do NOT pry the grill off from the front. In fact, there is no need to mess with it at all. Remove the entire right side trim including the grill to access the sub enclosure. It has quite a few fasteners and you will need a square-X bit to remove the cargo tie down points before removing the section of trim. You will need to remove the back section near the bumper first in order to to remove the right side trim. I did not fully remove it (really no need), but mostly removed it and folded it out of the way in order to gain access to the sub enclosure. Everything from then on comes out pretty easily. I mounted the amp in the spare tire well area right side - after I cut out a bunch of the foam to create a space. As an aside, I removed the spare, all the foam and built my own custom support for the deck. I already have a compressor, tire repair kit, tools, etc. from previous vehicle. The spare takes up a bunch of room. That's a personal preference. There is ample space to mount an amp in the area if you want to keep the spare, just need to be creative.


Upgraded Sub


A couple of critical things I have learned after the install. 1) There is no reason to duel tap the sub and center channel from the built in amp. The center channel (at least where I tapped in) has zero low frequency sound. This is apparently different in other years. 2) There is no need to tap into the sub wires under the center console. I would only do it right at the sub itself if I had to do this over. 3) You get some horrible feedback from the ANC system when first starting. I disconnected and viola, the problem went away. I also don't notice any additional noise in the cabin.

It sounds great. It really pumps out quite a bit of bass from that 8" kicker. I use the subwoofer level in the existing controls to adjust the volume level of the bass from the sub.

 

Excellent detail. Thanks for taking the time to document this process.


RFT!!!
Dave Kelsen
--
Most of us go to our grave with our music still inside of us.

 

Thank you for your post! I copycat your build 😅 same subwoofer but with Kicker key500.1 300w at 2 ohm. Very happy with the results. Next step is Jesse’s Phantom audio amp upgrade.

 

Nice install. Glad you are happy with the results. Did you happen to disconnect the ANC system as well?

 

Yes I did. Followed your steps to the T 😅 thanks again for the detailed write up!

 

Hey do you still have pic of how your amp is installed? I don't have spare tire and for now i just put mine on the foam. Looking for ideas on how to secure it. Thanks!