Key Takeaways
- A car subwoofer reproduces low bass (roughly 20 to 80 Hz) and is only part of a system: driver, amplifier, and enclosure.
- It works by moving a cone with a voice coil in a magnetic gap; clean cone travel is the one-way Xmax.
- Four types: component drivers, loaded enclosures, powered/active subs, and shallow-mount subs for tight spaces.
- Most subs are passive and need a mono (monoblock) amp; powered subs have the amp built in.
- The specs that matter are RMS power, one-way Xmax, voice coil impedance, and the T/S parameters that size the box.
A car subwoofer is a speaker built to reproduce the low bass your door speakers cannot, and it only works as part of a system: the subwoofer driver, an amplifier to power it, and an enclosure to control the sound off the back of the cone. This explains what a car subwoofer is, how it works, the types you can buy, and the specs that actually matter.
This is the overview of the category. When you are ready to pick a specific model, use our guide to choosing a car subwoofer, size it with the subwoofer sizes guide, and power it using the mono amplifier guide. Browse the full subwoofer collection any time.
What is a car subwoofer?
A car subwoofer is a speaker dedicated to low bass, roughly 20 to 80 Hz, the range that regular door and dash speakers cannot reproduce with any authority. It is not a plug-and-play part on its own. A subwoofer driver needs an amplifier to feed it power and an enclosure to control the sound wave coming off the back of the cone. Driver, amp, and box are the three pieces of a bass system, and all three have to match.
How does a car subwoofer work?
Audio current from the amplifier runs through a voice coil that sits in the gap of a magnet. As the current changes, the magnetic field around the coil pushes and pulls it against the fixed magnet, and that motion drives the cone in and out. The moving cone displaces air, and moving air at low frequency is what you feel as bass. To make deep bass loud, the cone has to move a large volume of air, which is why subwoofers have big cones and long travel.
The distance the cone can travel cleanly in one direction is the one-way Xmax, and it is one of the honest measures of how much output a sub can make without distorting. Because low bass is non-directional, one subwoofer run in mono handles it for the whole vehicle, which is why sub amps are mono. Here is a slow-motion look at the cone doing the work:
What are the types of car subwoofers?
There are four types you will actually shop between. They differ in how much you build versus buy, and how much space and power they need.
| Type | What it is | Best for |
|---|---|---|
| Component driver | The bare subwoofer; you supply the box and amp | Custom builds, best sound per dollar |
| Loaded enclosure | A sub already mounted in a matched box | A correct box without building one |
| Powered / active | Sub, box, and amplifier in one unit | Simplest install, tight spaces |
| Shallow-mount | A reduced-depth driver (often under 3.5 in) | Behind or under a truck seat |
Component drivers
A component driver is the bare subwoofer. You pick the box and the amp, which gives you the most control over the result and usually the best sound per dollar. The Audiomobile GT2 2010, a 10-inch driver with 400 watts RMS and 11.9mm of one-way Xmax, is a good example of a standard-depth component sub.
Loaded enclosures
A loaded enclosure comes with the sub already mounted in a box sized for it, so you skip the design and build. Our direct-fit truck enclosures loaded with the JL Audio 10TW3-D4 are an example: the box is cut on our CNCs to the vehicle, and the driver is matched to it.
Powered and shallow-mount subs
A powered, or active, subwoofer packs the driver, box, and amplifier into one unit, so it only needs power, ground, and a signal input. It is the simplest install and a common pick for tight spaces. Shallow-mount subs solve the space problem a different way, with a reduced mounting depth. The Wavtech thinPRO10 is 2.875 inches deep and the JL Audio 10TW3-D4 is 3.25 inches, both built to make real output behind a truck seat. This video breaks down active versus passive:
Sealed, ported, or bandpass enclosures?
The enclosure shapes the sound as much as the driver does. Sealed boxes are smaller and give tight, accurate bass. Ported boxes are larger and play louder around their tuning frequency. Bandpass boxes are specialized and loud in a narrow band. A quick way to see which way a driver leans is EBP, its efficiency bandwidth product, which is Fs divided by Qes: under 50 leans sealed, over 100 leans ported, and 50 to 100 works either way. The full tradeoff and how to build each is in the enclosure guides.
What specs actually matter?
Four numbers do most of the work when you compare subs:
- RMS power handling. The continuous power the sub is built to take. Match your amp's RMS to it, and ignore the inflated peak or max numbers on the box.
- One-way Xmax. How far the cone travels cleanly in one direction. Always read the one-way figure; a sub listed at a big peak-to-peak number is only moving half that each way.
- Voice coil impedance. Single or dual coil, and the ohm rating. Two 2-ohm coils in parallel present 1 ohm, two 4-ohm coils in parallel present 2 ohms, and two 2-ohm coils in series present 4 ohms. Wire to a load your amp is stable at.
- Thiele-Small parameters. Fs, Qts, Vas, and the rest set the correct enclosure. They are what turn a driver into a working bass system in the right box.
One spec-sheet detail to keep straight: the bolt circle diameter is always larger than the cutout diameter, never the reverse. For the parameter side in depth, see our enclosure and Thiele-Small guides.
Frequently Asked Questions
What is a car subwoofer?
How does a car subwoofer work?
What are the types of car subwoofers?
Do all subwoofers need an amplifier?
What is a shallow-mount subwoofer?
What specs matter most on a car subwoofer?
Sealed or ported enclosure for a car subwoofer?
Where to go next
Now that you know the category, pick a model with the guide to choosing a car subwoofer, settle on a size with the subwoofer sizes guide, and power it with the right mono amplifier. Driving a truck? The truck subwoofer guide covers behind-seat fitment. Or browse the subwoofer collection.
Want a driver, box, and amp matched for you instead of picking each yourself? Contact us. We cut the enclosures on our own CNCs and tune every system before it leaves the shop.
About the Author
Scott Welch is a Multi Time IASCA National and MECA World Sound Quality Champion, an active SQ judge since 2019, and the owner of Audio Intensity in Tullahoma, Tennessee. He cuts every Proline X enclosure on the shop's CNCs and tunes every customer system before it leaves. Audio Intensity is the original US importer for Goldhorn DSP and an authorized dealer for Prodigy, Crescendo, Image Dynamics, Wavtech, Tru Technology, and more.
