How to Hook Subs to Factory Radio in 8 Simple Steps

As an experienced car audio technician, I’ve installed hundreds of subwoofer systems over the years. One of the most common questions I get is “How can I add a subwoofer to my factory radio?” In this article, I’ll share everything I’ve learned through years of hands-on experience to help ensure you can safely and effectively integrate subs into your vehicle’s stereo.

Let’s examine the different options available, factors to consider, and step-by-step instructions for connecting subwoofers to your vehicle’s factory audio system. By the end, you’ll have a solid understanding of how to hook subs to factory radio.

Subwoofer Installation Options

The first decision is deciding how you want to integrate the subwoofers into your vehicle’s stereo. Here are the primary options:

Line-Level Outputs

Many factory radios have available “line-level” outputs that can be tapped into to feed an amplifier. These outputs provide full-range audio but at a lower voltage/power level than speaker-level outputs. An amplifier is still required to boost the signal to a level that can drive subwoofers. Tapping line-level outputs is usually the cleanest installation option.

Speaker-Level Outputs

If line-level outputs aren’t available, you can tap speaker wires before they reach factory speakers. This provides full-range audio at a higher voltage/power but introduces potential noise issues. A line-out converter (LOC) must be used to extract the low-frequency signal for the amplifier. This is a more rugged installation method.

Adding an Interface

For newer vehicles without any accessible outputs, an interface like the PAC AOEM+ can be purchased. These “piggyback” onto factory harnesses/modules and provide dedicated line-level outputs for an amplifier. Consider an interface if other tapping options aren’t feasible.

Factors to Consider

When determining how to best integrate subs with your factory system, weigh these important considerations:

• Vehicle Make/Model – Outputs and installation difficulty vary significantly. Research your specific year/model.
• Level of Disassembly – Tapping speaker wires often requires panel/trim removal. Consider labor required.
• Sound Quality – Line level is usually cleaner than speaker tapping which can introduce noise.
• Ease of Use – Interfaces simplify installation but add expense over direct tapping.
• Upgrading Head Unit – Replacing the factory radio provides the most installation options/flexibility long-term.
• Budget – Factor in costs of adapters, converters, amplifiers, and labor hours required.

How to Hook Subs to Factory Radio

Step 1 – Gather Your Gear

Before you start, gather all the necessary components:

• Subwoofer(s) and enclosure(s) suitable for your vehicle
• Amplifier sized properly to power subwoofer(s)
• A wiring kit and fuse holder
• Multimeter (helpful for testing factory outputs)
• Wire strippers, crimping tool, soldering iron (if needed)
• Electrical tape and cable ties
• Interface adapter or line-out converter (if needed)

Double-check that you have all the required parts before beginning disassembly work.

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Step 2 – Pick an Access Point

Carefully inspect your vehicle’s factory radio, connectors under the dash, fuse box, speaker wires, etc. Determine the best option:

• Test factory line-level outputs with a multimeter if accessible
• Evaluate speaker wire routes and access points under trim panels
• Consider an interface adapter if the above aren’t viable

Marking the planned wiretap points before disassembly helps plan your approach.

Step 3 – Disassemble Panels

Remove necessary plastic panels, trim pieces, and headliner material to access planned wire access locations. Carefully store hardware for reinstallation. Refer to your owner’s manual if needed.

Wear safety glasses when working under the dash and use plastic trim tools to prevent damage. Go slowly, taking before/after photos if needed.

Step 4 – Connect the Wires

With the tap points accessible, it’s time to interconnect audio sources and stereo components:

• Crimp or solder wire taps onto chosen factory wires
• Connect input wires from amplifiers to taps using crimp connectors or solder
• Run new power and ground wires to a fused distribution block near the batteries
• Run speaker wire to each subwoofer enclosure location

Use electrical tape generously and bundle loose wire neatly with cable ties.

Step 5 – Mount Subwoofer Enclosures

Find suitable, secure mounting locations for subwoofer enclosures based on your vehicle’s construction and cargo/passenger space. Options include:

• Trunk/cargo area (sealed if possible to avoid rattling)
• Under the rear seat (use sound deadening for maximum output)
• Rear floor/package shelf (secure firmly to unibody)

Use weatherproofing tape and sealant for any exterior panel modifications.

Step 6 – Amplifier Installation

The amplifier should be securely fastened in the interior passenger compartment, usually under a seat or in the trunk. Use self-tapping screws or bolts suitable for the mounting surface.

Connect speaker wire inputs from each subwoofer to corresponding amplifier output channels. Also, connect the remote turn-on wire to connect amp operations to the stereo/head unit.

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Step 7 – Finishing Touches

Almost done! Wrap up integration work by:

• Reinstalling trim panels, headliner and any removed interior pieces
• Programming the amplifier crossovers and settings to suit subwoofer(s)
• Concealing unsightly wiring and bundling neatly with cable ties or conduit
• Reconnecting the negative battery terminal temporarily for testing

Step 8 – Test and Enjoy!

After reconnecting the battery, power on the stereo and enjoy the fruits of your labor! Verify all connections by playing music at various volumes. Tweak amplifier controls until satisfied.

Reattach any remaining trim pieces that were temporarily removed for testing. And there you have it – subs successfully integrated into your factory stereo! Enjoy the added bass.

Upgrading in the Future

While tapping factory outputs allows sub-integration, upgrading your vehicle’s head unit can unlock even more options down the line. A quality aftermarket stereo provides dedicated subwoofer-level outputs, improved sound processing, Bluetooth/smartphone connectivity, and app-based controls.

When the time comes for an upgrade, your subwoofer system installation work makes adding a new head unit much simpler by reusing existing amplifiers and subwoofer wiring.

Troubleshooting Subwoofer Connection to Factory Radio

No installation goes perfectly smoothly 100% of the time. As an experienced car audio tech, I’ve encountered virtually every hiccup under the sun in my years turning wrenches. In this article, I’ll discuss some common issues that can arise when integrating subs into a factory stereo setup. Learning to methodically troubleshoot is key to keeping your bass bumping down the road.

No Sound from Subwoofer

The most frequent complaint I hear is a lack of low-end output despite everything “looking” correctly hooked up. When this occurs, systematically work through potential causes:

• Check the amplifier fuse and ensure power/ground wiring is terminated properly
• Verify signal wiring is hooked up to the correct amplifier input channels
• Inspect RCA connections and speaker wire splices for loose or faulty joints
• Confirm correct wiring polarity on signal and speaker wire connections
• Test audio signal strength reaching the amplifier with a multimeter
• Reset or try new amplifier gain settings

Noisy or Distorted Sound

A fuzzed, rattling, or otherwise degraded sound quality can stem from a variety of gremlins:

• Inspect RCA cable runs for proximity to power wires (can induce noise)
• Test speaker wire connection points for short circuits or loose shielding
• Check amplifier Gain is neither too high nor too low for the system
• Isolate signal wire grounding points from power/ground wires
• Look for faulty amplifier components like onboard fuse or capacitor
• Replace factory head unit if internal issues exist

External Noise Complaints

Whining, humming, or buzzing originating outside the vehicle may signal:

• Loose or corroded ground points between battery and vehicle chassis
• Needy alternator charging system putting out electrical noise
• Bad battery connection creating voltage drop issues
• Ground loop between the head unit chassis and amplifier ground wiring
• Poorly shielded antenna or factory harness wiring picking up noise

Bass Level Issues

Complaints of weak, booming, or inconsistent bass could mean:

• Incorrect amplifier Gain setting for subwoofer impedance/sensitivity
• Wrong subwoofer box enclosure size/parameters for the speaker
• Faulty crossover components like capacitors in amplifier
• Head unit EQ or sound settings boosted/cut certain frequencies
• Blown voice coils due to an undersized amplifier or over-excursion

The key is systematically troubleshooting one possibility at a time using a multimeter, audio test tones, and isolation techniques. With patience and a process of elimination, nearly any issue can be identified and resolved. Feel free to reach out if you need an extra set of ears!

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Frequently Asked Questions on How to Connect Subwoofer to Factory Radio

Can you connect a subwoofer to a factory stereo?

Yes, it’s possible to add a subwoofer to a factory stereo. You’ll need an amplifier and either tap into existing output wires or use an adapter with RCA outputs.

How to hook an amp up to a factory radio?

To connect an amplifier to a factory radio, you’ll need to run RCA cables from the amp to the radio’s outputs. Then run power/ground wires and connect the amp to your subwoofer’s speaker wire inputs.

How to connect subwoofer to car radio?

To hook up a subwoofer to your car’s stereo, you can run speaker wire from the sub to a line output converter. Plug the converter into the head unit and amp for power. The amp then pushes sound to the sub.

How do I connect my subwoofer to my music system?

Run RCA cables from your music system to a car amplifier. Use a speaker wire to connect the amplifier output to your subwoofer. Power the amp using battery power/ground wire connected to your music system remote turn-on lead.

Can I put a subwoofer in my car without an amp?

You can install a subwoofer but it won’t perform well without an amplifier. Amps boost head unit signals to levels that can drive a subwoofer’s woofer.

Can you hook up a subwoofer without a subwoofer output?

Yes, you can tap into a speaker wire running to your factory speakers and use a line output converter to isolate the low-frequency signal and feed it to an amplifier powering your sub.

Final Thoughts on How to Add Aftermarket Subwoofer to Factory Radio

I’ve certainly covered a lot of ground in this discussion on how to hook a subwoofer to a factory radio. From assessing factory options to troubleshooting potential issues, I hope sharing my first-hand expertise has helped shed some light on successfully taking on this common installation project.

As someone who has hooked countless subs to all manner of factory head units over the years, I feel I’ve got a pretty solid handle on tackling the challenges this niche topic can present. But at the end of the day, there’s no true single “right” way to accomplish integration – every vehicle is unique, and adaptable solutions differ accordingly.

The main takeaways I want to leave you with are to go slowly, methodically test everything, and don’t be afraid to get creative when standard practices don’t pan out. Taking the time upfront to scope out factory wiring capabilities and consider all installation angles will save loads of headaches down the road. An ounce of prevention is worth a pound of cure in this game!

And if issues do arise after everything is said and done, stay cool and use logical troubleshooting processes to identify the root cause. Chances are it’s a simple fix if you just slow down and analyze things step-by-step. We’ve all been there – no shame in tweaking a setup to get optimal performance in the end.

I hope sharing a behind-the-scenes look into my world as an experienced car audio tech who’s hooked subs to factory radios for eons has proven insightful. Please feel free to reach out if you need any other guidance on the topic. I’m always stoked to lend another perspective to help car audio lovers get their bass bumping sweet and clean.

Now get out there and start integrating some subs into your factory system! With the right knowledge and careful execution, I’m confident you’ll be cranking that low-end before you know it.