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.
