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How to Connect Subwoofer to Car Stereo Without Amp

How to Connect Subwoofer to Car Stereo Without Amp 1

Are you stuck figuring out how to connect a subwoofer to your car stereo without an amp? 

The process can be daunting, especially for a beginner, let alone experts with experience.

Luckily, this step-by-step post will guide you through the process and let you in on the best practices. 

Follow these steps actively to revolutionize your car music experience.

How to Connect Subwoofer to Car Stereo Without Amp

Step 1.    Purchase the Required Equipment and Note the Ground Rules

To connect a subwoofer to a car stereo without an amp, you need to get either an under seat, spare wheel, or bass tube subwoofer because they have an in-built amplifier. Such subwoofers are known as powered or active subwoofers and save you the stress of buying an external amplifier.

Before proceeding to buy the work tools and other requirements, assess whether your car’s stock stereo has RCA pre-outs.

If the stereo does not have RCA pre-outs, you must purchase either a line-out or hi-low converter to change the speaker output signal to an RCA preamp signal, making the transmission of sound signals from the stereo to the sub through RCA cables possible.

This guide will assume you do not have RCA pre-outs because most stock stereos are not fitted with them.

Next, you need to buy a wiring kit because subwoofers are not sold with wiring kits, unless your vendor included some. 

The wiring kit must include different sized cables and connectors. Here is a reference list of what to buy:

Tools or equipment for the task include:

Step 2.    Select a Suitable Spot for the Subwoofer

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Subwoofers require power to generate the bass you desire, meaning they dissipate heat. Therefore, you must find a well-ventilated and stable space in your car to keep the subwoofer. 

Make sure there is enough space around the subwoofer to allow for proper air flow and bass output.

By default, under-seat subs go under the seat, bass tube subs go in the trunk, and spare wheel subs go in the spare wheel space, but that should not be the guiding rule. 

Do not risk placing your subwoofer in a tight place as continued poor heat dissipation reduces the lifespan of the subwoofer and affects sound quality.

Once you find a suitable spot, leave your woofer there and continue to the next step.

Step 3.    Disconnect the Car’s Battery and Kill the Engine

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For your safety while undertaking the process, you must turn off the car and disconnect the positive and negative terminal wires of the car battery.

After killing the engine, pop the wood open and observe the battery for any form of corrosion first. 

If the battery is corroded, get a pair of gloves and goggles before proceeding to disconnect the terminals.

Following the battery assessment, use an adjustable wrench or any other fitting wrench to unbolt the positive and negative terminals. In most cases, you can unbolt the negative terminal only.

Place the negative and positive wires away from each other and ensure none of them are close to a metal surface and proceed to the next step.

Step 4.    Route the Power Wire Through the Firewall to the Subwoofer

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The power wire is usually red, but you should be careful with the labeling. You can easily spot it due to it being the longest among all the wires.

To ease this phase, look for a hanger, straighten it out and then create a hook at the end. The hanger will help you get the power cable through the firewall easily. 

The firewall is the metal chassis separating the engine from the sitting area.

Look for a clear opening running from the engine side through the firewall to the passenger side. 

You can light a torch down the engine area and observe if you can see some light come through to the passenger side.

If you do not find an opening, you have to use a knife to create one, but be careful not to cut the wires that transmit either signals or power from one car component to the other.

After finding or creating an opening, insert the hanger from the engine side to the passenger side and hook the power cable. 

Pull the power cable through the firewall to the engine side. Gently pull the power cable until enough of it reaches the battery.

Run the rest of the cable on the passenger side to the subwoofer. You can hide the wires under the car carpeting.

After getting the cable to the subwoofer, leave it there and execute the next phase.

Step 5.    Connect the Power Cable to the Fuse and Battery

Connect the Power Cable to the Fuse and Battery

Head back to the hood section to connect the power cable to the fuse and battery. Keep the cable protection conduit close.

Using pliers or a sharp knife cut about 15 cm of the power cable from the end that is supposed to be connected to the battery terminal. 

Strip both ends of the 15 cm power cable using a stripper. Using an Allen key, open one of the fuse holder’s terminals and connect the wire to it.

Proceed to protect the other long power cable from which you cut a 15 cm piece from with the cable protection conduit. 

After that, strip the end of the wire and connect it to the other end of the fuse holder. Now you have a fuse holder that is approximately 15 cm away from the end to be connected to the battery. 

Place the fuse in place and then proceed to connect the wire to the positive battery terminal. 

First, strip the wire and slide it into one crimp ring. Use a crimping tool to press the metal endings of the crimp ring to hug the wire tightly. 

Finally, slide the crimp ring down the positive terminal of the battery.

Step 6.    Run the RCA and Blue Remote Cable from the Subwoofer to the Stereo

Starting from the subwoofer, run the RCA and blue remote cable to the stereo. Do not run the cables through the same path the power cable lays to avoid audio signal interference by the flow of electricity.

Since the power cable went from the passenger side, lay the RCA and remote cables through the driver’s side. 

Tuck the cables underneath the side panels or carpets. Leave the cables and proceed to the next step.

Step 7.    Take Apart the Dashboard and Stereo and Connect the Converter and Cables

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Look for your car manual to determine the best way to pry your dashboard open and to reach for the stereo. 

Some dashboards are put together using plastic connectors while others require you to use a Philips screw to unscrew the components apart.

Follow the car manual and take the dashboard apart, gain access to the stereo and slide the stereo from its spot to access the speaker wires behind it.

Take the speaker cables and connect them to the speaker cables plugged into the stereo. The speaker wires are usually four with a fifth cable being the remote wire.

Rather than stripping the speaker wires, use plastic crimp connectors such as Posi-connectors to tap into the speaker signal. Then, connect the speaker wires to the line-out or hi-low connector.

The line-out or hi-low converter must have RCA pre-out ports that you can insert the red and white connectors of the RCA cable.

After plugging the red and white connectors into the pre-outs, connect the blue-remote wire to the blue wire connecting to the stereo. The blue wire to connect to is labeled antenna, amplifier, or remote.

Do not reinstate the dashboard or stereo to its initial state, proceed to the following step after evaluating whether you have connected the wires correctly and properly.

Step 8.    Attach the Ground Wire to an Exposed Metal Plug

Despite a powered subwoofer having an in-built amplifier, it must be connected to a grounding wire. The ground wire protects the amplifier in case of a power surge.

Head to where you have kept the sub and look for an exposed bolt or screw to connect the ground wire. Since the ground wire is short, ensure the bolt or screw is close to the subwoofer.  

Before stripping the ground wire and connecting it to the screw or bolt, ensure there is no paint on the bolt or screw. 

Paint hinders the proper flow of electrical charges. Using a paint scraper, scrape the paint off. If you do not have a paint scraper, use sand paper.

Strip the ground wire and tightly connect it to the metal plug. Finally, connect the ground wire to the subwoofer.

Step 9.    Connect the RCA, Power and Remote Cable to the Subwoofer

Complete the circuit by connecting the RCA and remote cable to the subwoofer. Plug in the white and red cables of the RCA cable into the RCA ports on the subwoofer and the remote wire to the signal control pin. Lastly, connect the power cable to the subwoofer.

10.  Reconnect the Battery Terminals and Test the Subwoofer

Head to the hood area and reconnect the terminals of the battery and switch the car on. Play some music to test whether the process was successful.

In case of any issues, check the connections for any loose wire contacts.

If the subwoofer works great, head back to the dashboard area, slide back the stereo and put back the dashboard to how it was. 

At this point, you would have successfully connected your subwoofer to the car stereo without having to buy an external amplifier.

Related Posts


Can I run a subwoofer without an amp?

Yes, you can run a subwoofer without an amp but the performance and sound quality will be significantly reduced compared to when an amplifier is used. Without an amp, the subwoofer will not have enough power to reach its full potential and will be unable to produce loud bass notes or deep lows. Additionally, the lack of an amplifier means that the subwoofer will be unable to handle higher frequencies and will sound muffled. To get the best out of your subwoofer, it’s highly recommended to invest in an external amplifier. This will allow you to control the volume and make adjustments as needed while providing high-quality sound.

Can we connect the subwoofer directly to the car stereo?

Yes, you can directly connect a subwoofer to your car stereo. However, for the best sound quality and performance, it’s usually recommended to use an amplifier in between the subwoofer and your car stereo. With an amplifier, you can adjust the volume of the subwoofer easily and independently from your stereo.

What happens if you play bass without an amp?

If you play bass without an amp, the sound will be quieter and not as full. Without an amp, the low-end frequencies that make up a lot of the character of bass sounds are lost. You may also encounter difficulty in keeping up with other instruments or vocals when playing live shows without an amp. Additionally, not having an amplifier limits your ability to experiment with effects and tone shaping. In general, it is best to use an amp when playing bass in order to achieve the sound you desire.

How much does it cost to put a sub in your car?

The cost of adding a subwoofer to your car audio system can vary greatly depending on the type of subwoofer you choose and the complexity of the installation. On average, expect to spend anywhere from $100 for a basic setup to over $1,000 for a more elaborate sound system with multiple subs and custom enclosures. Labor costs will also vary from shop to shop, so make sure to do some research and get estimates before committing.

Miles Walker is the founder and lead reviewer at CarAudioWise. com. With over 20 years of experience in the car audio industry, he is an acknowledged expert on all aspects of car audio technology and installation.

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