Car Stereo Upgrade: Subaru STI Edition

As one of World Wide Stereo's car audio specialists, I live and breathe cars every single day. When it came time to upgrade the audio equipment in my Subaru WRX STi, I knew from the get-go that I wanted a high performance stereo system, while keeping the stock interior panels intact. The result? A stealth system I can enjoy every day, and repurpose when it's time for a new ride.
Check out our finished product in the video and photos below!

Planning the system upgrade.

The build for my Subaru WRX STi stereo upgrade was simple. My installer, Frank, and I wanted the new system to play as true-to-life as possible throughout the volume spectrum. We also wanted it to be an “everyday build,” so I could fit two amplifiers and a subwoofer into the trunk without gobbling up too much room. This car is my daily driver, and I still needed to fit things like luggage and grocery bags.


I already had the Kenwood DDX9903S in place, which is a great platform to build off of. I’m an Android user, so it was very important for me to have a touchscreen with Android Auto built-in to ensure I could access my Spotify and TIDAL playlists, as well as navigation platforms like Google Maps and Waze. I also wanted the ability to control the system with voice commands, so I don’t have to remove my hands from the steering wheel or shift knob while driving.

Subaru WRX STi front
Subaru WRX STi interior
Subaru WRX STi Kenwood Receiver

Choosing the right speakers.

For the front speakers, it was a no-brainer to go with something from Focal’s car audio selection. After some deliberation, Frank and I moved forward with Focal’s Utopia Be 165 W-RC 2-way 6-1/2” component speaker kit from their Utopia Be series. The pure Beryllium tweeters are extremely musically accurate without sounding “bright.” The accompanying woofers are built to belt out great mid-bass response, which helps bring the sound of the trunk-located subwoofer closer to the front of the car.

I knew we wouldn’t be using the included crossovers, as I wanted the tuning flexibility of going “active.” In this type of system, an amplifier is installed and wired to power each speaker separately instead of using the crossovers. For example, the JL Audio 300/4v3 amplifier installed in my Subaru is wired in such a way that channels 1 and 2 power the tweeters in the dash, and channels 3 and 4 power the woofers in the doors.

The rear speakers run off of the power supplied by the Kenwood touchscreen, so we went with a pair of speakers that thrive off that type of power and sound really good, too: Focal’s 165 AC Access 2-way 6-1/2” coaxial speakers. What’s unique about these speakers is that the tweeters sit angled up on a rotatable post. This allows them to be twisted to fire the high frequency audio tones up towards the your ears, allowing you to hear more detail. The end result: an even better listening experience.

Focal Utopia Be 165 W-RC 2-way component speaker
Subaru WRX STi replacement speaker
JL Audio 300/4v3 amplifier

Bringing the bass with JL Audio.

When searching for the right subwoofer, I wanted something that could deliver a clean and loud bass response. The JL Audio 10W6-series subwoofer was the no-brainer solution for me. I had the option to get the JL Audio CS110G-W6v3 10" sealed subwoofer that comes with a rugged, compact, sealed enclosure, which was a big bonus for me. Not only does it sound fantastic, but it can also be easily removed from my trunk in case I need to make room for groceries.


A JL Audio 600/1v3 600-watt monoblock subwoofer amplifier was selected to drive the subwoofer. It’s a bit more power than the subwoofer needs, but I wanted to ensure perfect sound quality regardless where the volume was set, so that extra power comes in handy.


Both amplifiers aren’t contenders for the “Smallest Amplifiers in the World” competition, but they are compact enough to live on the back of the passenger-side rear seat of the car. That keeps them up off the floor so they aren’t taking up valuable trunk real estate.

To pull power from the battery located under the front hood, a JL Audio XD-PCS2-2B 2-gauge power kit was employed. Frank ran the thick power wire to the trunk area where it plugs into a compact distribution block. From this block, slightly smaller 4-gauge power wires emerge and run to the power inputs on the JL Audio amplifiers. This distribution block is fused to help protect the electrical system of the car, as well as the amplifiers.

JL Audio Subwoofer
Subaru WRX STi back exterior

Sound deadening with Dynamat.

The Subaru STi is a ton of fun to drive, but it rattles like a tin can loaded with pebbles. So we decided to enhance the sound quality inside the car and reduce outside noise with a one-two punch from Dynamat. When the speakers were installed, Dynamat Xtreme was applied to the metal door pieces to help combat road noise and limit resonation. To further insulate the doors, a Dynamat Dynaliner kit was placed over the Dynamat that had just been laid into place. (Dynaliner is a closed cell foam that helps further stop road noise from entering the cabin of the Subaru.)

Giving the new system a test drive.

After giving the system a quick tune, the speakers were slowly broken in over the course of about two and a half weeks. Once they had time to truly shine, I brought the car back into the bay for the final tune, which took about a half hour to complete.


The final result of this stereo replacement is pretty darn impressive; I just love the way it sounds. I am a perfectionist, though, so I will constantly be working to improve the sound. I didn’t sacrifice too much space, so I am able to put luggage or other things into the trunk without the amplifiers or subwoofer getting in the way. The Focal speakers are all tucked behind the factory speaker grilles, so the new speaker system looks like it was installed into the car from Subaru. All of the wishes on my audio upgrade checklist have been checked off.

Interested in upgrading your car stereo? Learn more about our car installation services and contact us today to see how we can help.

Subaru WRX Sti

Featured products in this project

Meet the System Installer

Chris Mulhearn

Chris Mulhearn

Sales & System Designer
Montgomeryville Showroom

215-368-8343, ext. 412


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