Based on discussion in this thread: Any interest in a writeup for 5th gen JBL nav system overhaul? I am posting a write-up for how to replace the stock JBL system in a 5th gen 4R with a new amplifier, speakers and sub, while retaining the stock H/U and all of its functionality.

I'll post this in several individual posts over the next few days. Feel free to ask questions along the way.

Objectives
I wanted to replace my factory JBL system while retaining the stock HU and all of its functionality (satellite radio, BT, aux, etc.). In this project, I replaced all factory JBL speakers (including the sub) and added an aftermarket amplifier to power the new speakers.

This project is not for the faint of heart. It requires significant wiring splicing, panel removals, and other modifications that could render the system inoperable. That said, it is a straightforward project if you have the requisite skill sets, plan appropriately and keep track of each step in the process along the way.

General approach
We are basically going to convert the output signals from the JBL stock amplifier into line level signals, combine them to achieve a stereo, front & rear output signal, then use a DSP to normalize the signals, feed the signals into an aftermarket amplifier to push to the individual speakers. Here’s what the signal path looks like:

Stock H/U --> Stock amplifier --> signal summing interface --> DSP to normalize the EQ --> aftermarket amp --> speakers

Ok, why do we have to take this approach?

We can’t go from the stock H/U directly to an aftermarket amplifier. The outputs from the stock H/U are proprietary, digital signals, which makes the H/U useless without its amplifier counterpart.

The stock JBL system has 9 discrete channels/speakers. The amplifier has internal crossovers that send only high-pass (HP) signals to the dash speakers, only MP signals to the front doors, and MP/HP range to the rear doors and hatch. The sub is obviously a discrete channel receiving only a LP signal. If we want to achieve a true stereo approach that allows for front/rear fading, we need to use signal summers to combine those discrete outputs into full range outputs the amplifier can accept.

We need a DSP to normalize the EQ. Stock systems are often tuned specifically for the vehicle and also to allow the system to reach maximum volume…BUT this comes at the cost of sound quality. I wanted to “clean” the stock amplifier’s outputs to remove any preset EQ curves and send the aftermarket amplifier a flat output.

I decided to use JL Audio exclusively for this project, primarily due to my history with this brand and also because of their DSP products that fit this application perfectly. Here are the parts I used:

Speakers
(2) JL Audio C2-650x (Rear doors & rear hatch)
(1) JL Audio C2-350x (Front dash)
(1) JL Audio C5-650x (Front doors)
(1) JL Audio 8W3v3-4 (Subwoofer)

DSP
(2) JL Audio CL-SSI (used in 2-way mode, to allow for complete fading capability, the first SSI combines the front signals, the second one combines the rear)
(1) JL Audio CL441dsp (takes outputs from SSI and normalizes EQ)

Amplifier
(1) JL Audio XD600/6 (single amp to power all speakers)

• Ch 1 & 2 – front speakers, dash and door wired in parallel

• Ch 3 & 4 – rear speakers, rear doors and hatch wired in parallel

• Ch 5 & 6 – bridged to subwoofer

The next post will focus on how we pull all of this together for the install. I'll also give some recommendations for where to purchase the speaker mounts that actually fit (there are tons of places that sell mounts that are claimed to fit, but do NOT).

Don't worry, yes, this next post will include pics.

Thanks Helix! I appreciate the time and effort you are giving us on how to do this! Ihave changed my speakers out less the Sub and Gate speakers. This write-up will help tremendously. Thanks again for sharing your knowledge!

...nice to see you're back, @Helix26404 . looking forward to reading your write-up.

Hi Preston,

This post promises to be an extremely 'refreshing' piece of work ('Important' would be far more accurate), but still my comment here is an understatement. There are many posts here on speaker upgrades and amplifier installs but not one that I can find pertains to the JBL (James B. Lansing) brand HU, D/A signal processing, gain structure, and it's amplifiers!

I've written a few (gen-5) '4Runner' audio system essay/tutorials, but never have I approached the subject from a JBL audio system POV because I don't have that system in my truck... So glad to see that someone has 'FINALLY' taken the time to give the JBL audio system the attention that it so respectfully has earned!

Best to you!

This isn't entirely accurate. There are four pairs of wires that go from the H/U to the stock amp in the rear. Two of these are right and left analog line outs which are full range and unaffected by the volume or balance controls. Another pair is the digital signals that control the amp. And the last pair is another analog audio signal like the first but it is only used for the navigation voice (and maybe a few other sounds).

Doing something similar for the 5th gen which is wired different...
Dash and doors in parallel
Rear door and hatch in series
Sub independent channel.


5th gen JBL stereo upgrade build Diary

New here and wanted to say thanks, read through this and many other posts, found this one of the most helpful. I am doing an audio overhaul of my own and hope to share my experience, for better or worse. Can't hurt to have a variation in setup as my approach may encounter different things along the way. 2018 Limited w/ JBL upgrade here also.

Ditch the radio, saves a lot of headache and you get a much better deck with carplay/android auto.

If youi just have to keep the OEM deck, get this Amplifier Integration Interface for Select 2014+ Toyota and Lexus vehicles with Premium Amplified Sound Systems - PAC

Don't waste time and money on a DSP to correct the factory limitations. The integration part will give you f/r/sub preouts with no OEM equalization and no bass roll off.