How to Connect Subwoofer to Car Stereo Without Amp


Jamming out to music in the car while on a road trip creates one of the greatest memories. Connecting subwoofers to your car audio can be a bit tricky if you do not have an amplifier.

Well, let’s find out how to connect a car subwoofer without an amplifier.

As a general rule, connecting a subwoofer to the car stereo without an amplifier requires an active subwoofer. If you have a powered subwoofer, connecting it is straightforward, and the only thing to do is to plug its jack wire with the installed stereo.

As an Amazon Associate, ImproveCarAudio will receive a small commission from qualifying purchases made through the links in this article.

Tip: As you know, typical car subwoofers require an external amplifier. The most popular subwoofers which you can connect directly with the stereo are active subwoofers.

My favorite is the thin but high-performing under-seat Rockford Fosgate PS-8 Punchwhich you can install in nearly every car thanks to its height of barely 3.3″.

In the article below I will show you which subwoofer types work the best when connected to the car stereo without the amplifier, and how to wire them.

How Does a Car Subwoofer Work?

A subwoofer gives you deep thumping bass that cannot be produced by standard speakers.

Any sound system without a good subwoofer might sound flat and not dynamic. The subwoofer produces low-frequency sounds, leaving the tweeters to create high-frequency sounds like vocals. The low frequency is typically in the range of 20Hz to 100Hz. Human ears have a hearing range of 20Hz to 20,000Hz. 

A benefit of having a subwoofer for bass is they are not dependent on the placement. Since low frequencies do not need to be strictly directional towards ears, it does not really matter where in the car you install the subwoofer.

do i need amplifier to connect car subwoofer

Although the majority of subwoofers are installed in the trunks, many find their places below the seat or inside the spare wheel. 

How to Connect Subwoofer to a Car Stereo Without Amplifier 

Connecting the subwoofer to the car audio will depend on the subwoofer type, and there are two ways:

  • for passive subwoofers
  • for powered subwoofers

Connecting a passive subwoofer

A passive subwoofer, which in other words means a speaker without a built-in amplifier, can be connected to the car stereo in the same way as any other speaker.

If you have existing speaker wires in the area where the subwoofer will be installed, connect them with a subwoofer wire. And that’s it. You will not get a shattering bass by wiring rear speaker output as a subwoofer output, but you will get a lower bass frequency in comparison to the speakers.

If there are no existing speaker wires, you have to drive wires from the head unit harness, the same way as you would for the car speakers. If you would like to learn a few tricks about wiring car speakers, check out this article about running new car audio wires.

Before starting any work with car audio, make sure to disconnect a ground wire from the car battery.

Connecting a powered subwoofer

The powered subwoofer connects to the stereo in the same way as the standard amplifier. This process is straightforward, and most of the active woofers come equipped with all the necessary wires, so let’s start:

  • Disconnect ground wire from the battery
  • Run power cable from the car battery to where the subwoofer will be installed. Do not forget about the main power fuse, which has to be placed close to the battery. Inside the cabin, run the power wire under the carpet to avoid any wire damage.
  • Remove the stereo from the vehicle’s stereo mounting dock to gain access to the wiring harness and outlets on the stereo’s rear panel.
  • Run the RCA signal wires from the car stereo to the subwoofer. Same as for the power wire, run the RCA cables underneath the carpet. Do not run RCA and power wires together. That can cause sound distortions.
  • Ground a subwoofer in the back of the vehicle. Make sure you use metal to the metal connection without any paint between the car body and the wire.
  • If your subwoofer is equipped with the control wire, run it from the woofer to the place you will use it. It can be either on the dash or close to your seat. Just make sure the steering panel will be easily accessible and will not cause interruptions while driving. 
  • With all connections done, place a removed earlier ground battery wire on the battery negative terminal and screw it back, ensuring a stable connection.
how to connect car subwoofer to factory stereo

Can I Connect a Subwoofer Without an Amp?

The amplifier’s job is to amplify a signal, and this power is required by large magnets in the bass speakers.

In most cases, if you want louder and distortion-free sound, you would get an amp. If you, however, decide not to use an amplifier and still want to have clear and strong bass at the same time, you should consider installing an active subwoofer.

On the other hand, if you can deal with some distortion in your sound and maybe some loss of loudness, just using the built-in amp that comes in head units should be sufficient. In these cases, however, the large passive subwoofer will not act as it should. Instead, you will hear a full range of distorted but not even close to the real bass sounds. 

Here are the benefits of using an amplifier with your standard subwoofer:

  • clear and real bass
  • louder sounds
  • low distortion 

Which Subwoofer Type Can I Connect to a Car Stereo Without an Amplifier?

The best, and I think only one type of subwoofers that will work without an external amp, are active subwoofers. These types of subwoofers are generally compact and not as strong as large enclosures with 12″ woofers. 

If you need decent enough bass without much hassle, an active subwoofer is an excellent option to choose from. And let us be honest, a car stereo without any bass is not worth it. 

They come in several popular sizes and shapes (links to Amazon open in the new windows):

  • Under-seat subwoofers
  • Bass Tubes
  • Spare wheel subwoofers

Under Seat Subwoofers

Under-seat subwoofers are most often installed in cars, especially when the trunk has limited space or is disconnected from the passenger cabin space.

For example, in sports cars with a centrally placed engine, there is no other way than to install a flat box with a slim-type subwoofer. A great example of the high-performance under-seat subwoofer is the Rockford Fosgate PS-8 Punch that, thanks to its 3.3″ height, can be installed in nearly every car.

how to connect car subwoofer without amplifier

Bass Tubes

Next up are bass tubes. If you happen to have a smaller car, these are the ones to go with. Bass tube subwoofers do not take up much space and are easy to fit. They can come in different sizes as well. 

The majority sizes can range anywhere between 6 to 12 inches. The speakers will be enclosed in a ‘tube’ – thus the name. It is a pretty good way to add some bass to the overall sound system without taking too much space in the trunk. 

Bass tubes are known for producing softer bass compared to other subwoofers, and if you are not looking for strong “kicks,” an excellent tube worth considering is the MTX Audio RT8PT.

how to connect subwoofer to car stereo without amp

Spare wheel subwoofers

Have a room in the spare wheel? Great. You can utilize this space in the trunk and install a subwoofer there. A subwoofer can be placed either inside the spare wheel or instead of the spare wheel if you do not have one. 

The main benefit is that you will not use any space from the trunk, and the subwoofer itself can be bigger and stronger than under-seat models. Choosing the right woofer depends on the installation possibilities and individual preferences, but for me, the absolute best is JBL Basspro Hub with its 12″ flat speaker.

Conclusion 

Connecting a subwoofer to a car stereo is not that difficult if you know how to do it.

Now that you know how to connect a subwoofer to a car stereo without an amplifier, go ahead and enjoy more bass from your new and improved sound system. 

Martin

Welcome to ImproveCarAudio! I am Martin, and I love to write about everything related to car sound systems. I strive to provide the most accurate and helpful information about car audio through extensive research, as well as my experience with car audio installations.

Related Articles