Introduction
Upgrading your car's factory stereo system can transform the listening experience in your vehicle. While simply replacing the head unit or speakers can provide an improvement, rewiring the system from scratch allows for complete customization and the ability to add more powerful amplifiers and subwoofers. Rewiring the system properly is crucial for achieving crisp highs and thumping lows. In this guide, I will walk through the full process of rewiring a car stereo system, from choosing the right gear to connecting everything for optimal sound.
Step 1: Choose New Stereo Head Unit
The first step is selecting an aftermarket stereo head unit to replace your factory one. Look for a head unit with at least 50 watts RMS power per channel, pre-amp outputs to connect amplifiers, and the latest connectivity options like Bluetooth, Android Auto, and Apple CarPlay. Brands like Pioneer, Kenwood, Alpine, and Sony make excellent head units with high-quality internal amplifiers for powering speakers.
For my Honda Civic, I chose the Pioneer DMH-1700NEX head unit for its 7-inch touchscreen, built-in Google Assistant, and 5 volt pre-amp outputs. This will provide a solid foundation to build out the rest of my system.
Step 2: Choose Speakers, Amplifier(s), and Subwoofer(s)
Now it's time to select new speakers, amplifiers, and subwoofers to really give your system some power.
Speakers
Look for component speakers with separate woofers and tweeters. This allows you to place the tweeters higher in the doors for better highs. Popular brands are JBL, Infinity, Rockford Fosgate, and Alpine. Match the speakers to the available channels on your head unit.
For my build, I'm installing JBL GTO609C components in the front and JBL GT7-6 coaxials in the rear.
Amplifiers
Adding at least one amplifier will help provide clean power to your speakers. A 4-channel amp can power both front and rear speakers, while a 2-channel amp is ideal for just the front. Look for amplifiers that output 45-100 watts RMS per channel. Brands like Alpine, Rockford Fosgate, and JL Audio make reliable amplifiers.
I'll be running a JL Audio JX400/4 to power my front and rear speakers.
Subwoofers
No system is complete without hard hitting bass. Look for subwoofers in 10, 12, or 15-inch sizes from brands like JL Audio, Rockford Fosgate, and Kicker. Make sure to get a powered subwoofer enclosure or an amp with enough power to drive your sub(s).
For my Honda Civic, I'm going with a single Kicker CompC 12" in a ported enclosure powered by a Rockford P300-1 amp. This will provide plenty of tight bass.
Step 3: Sound Deadening
Before wiring up your new gear, apply sound deadening mat to dampen external noise and vibrations for better sound. Brands like Dynamat and Kilmat make excellent deadening mats that stick to door panels and other surfaces. Cover as many areas as possible, focusing on doors and the rear hatch.
For my Civic, I used Dynamat Xtreme to treat the doors, rear hatch, and roof which made a huge difference in reducing road noise and vibrations.
Step 4: Rewire the Head Unit
Now it's time to wire up your new head unit.
- Disconnect the battery before beginning work.
- Remove the factory head unit and disconnect all harnesses and connectors.
- Connect the head unit power harness adapter for 12 volt constant, 12 volt ignition, and ground connections. I used a Metra 70-1721 wiring harness.
- Connect the speaker outputs if you are only running speakers from the head unit. My Pioneer has front, rear, and sub RCA pre-outs instead to connect amplifiers.
- If installed, connect steering wheel control and backup camera harnesses. An adapter like the Axxess ASWC-1 retains steering wheel controls.
- Mount the head unit in the dash opening and test it for proper operation before moving to amps and speakers.
Step 5: Install Amplifier(s) and Subwoofer(s)
Time to mount your amplifiers and subwoofer enclosure.
- Find a clean mounting spot for amps like the trunk or under seats. Use an amp wiring kit like the NVX True Spec 4 Gauge for power and ground connections.
- Mount your pre-fab subwoofer enclosure or custom box securely in the trunk. Make sure subs fire rearward.
- Run 8 gauge power and ground wires from the amp install location to the sub box. Use thick gauge speaker wire for sub amp connections.
- Connect RCA cables from head unit pre-amp outputs to amplifier inputs. This carries the signal from the stereo to amps.
I mounted my JL and Rockford amps under the front seats and my ported Kicker sub enclosure fires rearward in the trunk. 8 gauge wiring connects everything.
Step 6: Install New Speakers
The last wiring step is to install your new front and rear speakers.
- Remove factory door speakers and panels.
- Mount component woofers and tweeters in optimal locations for best sound. Tweeters should be ear level.
- Run new speaker wire from amp speaker outputs to crossover inputs, and then to each speaker. Use 16 or 14 gauge wire.
- Connect speaker wire outputs from crossovers to the woofers and tweeters. Observe polarity.
- Install grilles and reassemble door panels.
My JBL component speakers required custom mounting of tweeters in the A-pillars at ear height for excellent imaging. The woofers fit perfectly in the factory door speaker locations.
Step 7: Tune the System
With everything wired up, it's time to tune your system for the best possible sound.
- Set amplifier gains properly with an SMD DD-1 or similar tool to avoid distortion.
- Adjust balance and fader on the head unit for ideal front/rear speaker volume.
- Set the crossover filters on amplifiers to bandpass frequencies to speakers.
- EQ head unit and amps for flat response. Boost bass and reduce highs slightly.
- Adjust subwoofer phase and cutoff frequency for tight, punchy bass.
Proper tuning resulted in crystal clear highs from my front components and hard-hitting lows from the sub. The system achieves an immersive soundstage throughout the interior.
Conclusion
Completely rewiring your car stereo enables you to build a system tailored exactly to your needs for the best possible listening experience. While it requires time and effort, the end result is well worth it. With high-quality gear, proper installation, and tuning, you can achieve remarkable crisp highs and thumping lows. Just follow these steps and take care with the wiring, and your custom stereo will sing. Let me know if you have any other questions!