How To Install A Subwoofer To A Factory Stereo – 8 Easy Steps In No Time

If audio quality is important to you, then a factory stereo is likely to leave you feeling flat.

Let’s face it, car manufacturers have other things on their minds and a factory sound system is often an afterthought. If you want bass that sounds like your car’s about to take off, then you’re going to have to go aftermarket.

Car Stereo With Adjustable Volumes

A whole new aftermarket sound system might be intimidating. As well as being pricey, you’re going to have to deconstruct your dash.

But installing a subwoofer on your factory stereo is a quick job that gives you bad-ass bass, without a big investment.

You can install an aftermarket subwoofer in an afternoon, and by keeping your factory stereo you’ll keep all the factory controls you’re familiar with.

So let’s go back to bass-ics. Before we get to the step-by-step guide for installing your subwoofer, let’s get to know the difference between active and passive subwoofers. Then we’ll get under the hood.

Active vs Passive Subwoofer

You can choose either an active sub, also known as a powered sub, or a passive – unpowered – sub for your factory speaker. Both will work great to boost your sound system, but it’s important to know the difference before you get to work.

What Is An Active Subwoofer?

Active subs are also known as powered subs. They have their own power source – usually a built-in amplifier. That means you don’t need to install an amp alongside your sub, which can simplify the process.

But because of the built-in amp, they’re best used in systems where you only have one subwoofer. That makes placement more important because you don’t have multiple subs raising the roof.

What Is A Passive Subwoofer?

Passive subs, known as unpowered subs, don’t have a built-in amp. If you’re installing a passive sub into your car sound system, you’ll need to hook an amp up to the system too. It’s not too much more work, but it is an essential component.

Passive subs need an amp, so you’ll need more equipment to install these to your factory stereo. But they do give you the flexibility of adding more subs to the system.

Passive subs also tend to be cheaper than their active cousins, and they’re more compact. That comes in handy when you’re working in a small space, such as a vehicle.

Now you know about active/passive subwoofers, here’s an easy-to-follow, step-by-step guide for installing either variety of subwoofer to a factory stereo.

How To Install A Passive/Unpowered Sub And Amp

First, let’s take a look at passive subs. If you’ve got a small vehicle, you’ll appreciate saving space with a smaller sub.

Step One: Disconnect The Battery

Before working on your car’s electronics, disconnect the negative terminal of your battery. Ensuring there’s no power in your system will keep you save from an electrical mishap.

Step Two: Place Your Subwoofer

Locate a space for your subwoofer and the housing. Usually, you can find space in the rear of the vehicle or under the rear seats.

Step Three: Secure Power Wire

Secure your power wire to the positive terminal of the battery and run it to the amplifier. You’ll have to find a gap in the vehicle’s firewall to get it to the cab – find this by following the factory wires, and see where they enter the cab. And you may want to cover the portion of the wire in flex loom tubing to protect it from the heat of the engine.

A good wiring kit will include a fuse, which you should install as close to the battery as you can. This will keep you safe in the event of a power surge from your battery.

Run the power wire through the vehicle and connect it to the amplifier.

Step Four: Grounding The Amp

With a short black wire, you’ll want to ground the amplifier to a piece of metal in the vehicle – anything painted or plastic won’t do. Grounding the amp will make the system safer, as well as reduce additional signal that might mess with your audio quality.

Step Five: Connecting The Stereo To The Amp

Disassemble the dash, remove the factory stereo and find the wiring harness behind it. You’ll need to identify the speaker wire and tap into it, adding a connection that will run to your amp.

You can cut and splice into the wires, but using posi taps is a great shortcut for getting your speaker wire in.

Step Six: Connect Power And Ground To The Wiring Harness

While you have the wiring harness out, connect the power wire for the amp to the wiring harness. This will turn the amp on with the stereo, and off when the stereo’s off. You can connect the ground here to the ground wire coming from the wiring harness, too.

Step Seven: Connect The Speaker Wire To The Line Output Converter

Once you’ve connected your speaker wire to the wiring harness, you can run it back to the terminal on the line output converter. This is necessary because few factory speakers have pre-amp outputs.

With the speaker wire connected to the LOC, you can connect the RCA connectors to the LOC and then run them to the amplifier. Choose the opposite side of the vehicle from where you ran the power wire: this keeps the signals separate.

Step Eight: Connect Your Amp And Sub

Now you have everything wired in, you can connect the RCA cables to the amp and hook the amplifier up to the subwoofer with some heavy-duty speaker wire. Your new sub will be good to go once you reconnect the battery. Give it a whirl!

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How To Install An Active/Powered Subwoofer

If sound quality is your number one priority, then you’ll consider a powered subwoofer. With a deeper and richer sound, they’ll take your tunes to another level.

Installing a powered subwoofer is an identical process to an unpowered sub, only, in this case, the amplifier is built into the subwoofer. You’ll run the power wire directly to the sub, and ground the subwoofer directly to the vehicle.

You should also be able to plug the RCA wire directly into the sub once you’ve run it through from the factory stereo.

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Safety Precautions

Installing a subwoofer into a factory stereo will take your sound to the next level. But there are a few things you need to know to protect yourself and your system while you work.

  • Always disconnect the battery before doing any work to your car’s electronics. You can disconnect the negative terminal to take your battery out of the system, and you’ll be safe to get under the hood.
  • Take care of your wires to keep your car’s electronics in good condition. Ensure the wires take gentle curves rather than sharp bends on their journey to your subwoofer to reduce wear and tear.
  • Test your system with the gain down. Although you’re eager to crank the volume up to 11, when you test your sub you should start at lower volumes with the gain down. Putting a huge gain through your sub first thing could overload the system.
  • Add a capacitor to the system if you’re head-banging to high volumes. A capacitor will keep the voltage stable as the bass in your audio varies and can extend the lifespan of your sub.

    Add the capacitor to the system right next to the amp and ground it with the same wiring.

Wrapping Up…

If you care about audio quality, but don’t want to dive into the deep end of a full aftermarket sound system, then adding a sub might be the way to go.

Installing a sub on your factory stereo is easy once you know how. You get elevated bass while keeping all the factory features you’ve come to love.

Get your hands on the right equipment and our step-by-step guide will see you right. You’ll find your sound system hitting new lows!

Installing a subwoofer doesn’t have to be complicated – in fact, it’s pretty bass-ic.

Robert Muñoz

I’m Robert, a US-based auto electrician, auto mechanic, trained engineer and fanatic about all things motor vehicle. After studying engineering in college I returned to my original passion - car mechanics - and I ran a garage for a number of years serving my local community. Through my garage, I got involved in numerous road safety campaigns in my local area until eventually, I decided to share what I've learned with the world. Know more about me... You can follow me on LinkedIn.

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