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What is a subwoofer? What to know about this bass-boosting speaker

How do subwoofers work and what’s the best subwoofer? Here’s what you need to know.

Elizabeth Thorn
| Updated on
What is a subwoofer? What to know about this bass-boosting speaker© 2023 SvetaZi / Shutterstock

Whether you’re blasting a drum solo in your car, setting up your home theater system to watch the new Avengers movie, or building a stereo system for your band, you’re probably searching for that deep, juicy bass. To achieve that kind of sound, you’ll need a subwoofer.

A subwoofer is a loudspeaker that reproduces low-pitched frequencies such as bass and sub-bass. The subwoofer will take low-pitched audio signals and convert them into sounds that woofers aren’t able to generate.

The result is a deep, full-bodied sound that you can feel if you’ve got the speaker system set up just right. How do subwoofers work, what’s the best subwoofer, and do they really make that much of a difference in your overall sound system? Here’s what you need to know.

What is a subwoofer?

If you have a subwoofer, then there must also be a woofer, right? Correct. Most woofers or regular speakers can only produce sounds down to about 50 Hz. Subwoofers produce low-frequency sounds down to 20 Hz. Hence the name “woofer” comes from the deep, roaring sound that dogs make when they bark.

While the difference between the 50 Hz threshold of most speakers and the 20 Hz threshold for subwoofers sounds trivial, the result is noticeable. Subwoofers let you feel the sound of the bass in a song, movie, or any other sound that you’re listening to. The lower the low-frequency response of a subwoofer, the stronger and juicier the bass.

Because these tones are so low, some people actually aren’t even able to hear the bass that booms out of a subwoofer. That’s why the feeling component of a subwoofer is so essential.

Young, healthy human ears are only designed to hear sounds with a frequency down to 20 Hz, meaning that it can sometimes be difficult for middle-aged human ears to hear sounds that deep. With a subwoofer, even if you can’t hear it, you can certainly feel the vibrations.


How do subwoofers work?

Subwoofers connect to the other speakers in a full sound system. If you’re playing music at home, you’ll have likely connected the subwoofer to your audio receiver. When the music plays through the speakers, it’ll send low-pitched sounds to the subwoofer to reproduce them effectively.

When learning about how subwoofers work, you might encounter the two types, active and passive. An active subwoofer is also known as a powered subwoofer, as it comes with a built-in amplifier. Passive subwoofers require an external amplifier. If you choose to go with a powered subwoofer, you’ll need to invest in a subwoofer cable as you’ll have to connect it to the sound system’s receiver, as mentioned above.

You’ll notice that in home theater sound systems, subwoofers are the largest speaker. Is bigger better? Yes! The larger the subwoofer speaker, the deeper the sound is going to be. Only physically large speakers are able to produce the deep tones you hear coming out of a subwoofer.

What about the vibrations? How does that work? The effectiveness of a subwoofer largely depends on the placement of it. Expert audio engineers suggest placing subwoofers:

Under furniture. If you really want to feel the vibrations coming from deep, rich sounds in a film or musical piece, placing it under your furniture, such as a couch or a chair, can enhance those sensations.

Next to a wall. Place your subwoofer box next to a wall so that the outgoing sounds reverberate off the walls and strengthen the bass.

How do subwoofers work

How to choose the best subwoofer

Similar to regular speakers, subwoofers come with specs that make a difference in the purchasing process. Depending on what you’re after, here’s what to look for.

Frequency range

The lowest frequency of a subwoofer is the lowest sound a speaker driver can produce. The highest frequency is the highest sound the driver can attain. The best subwoofers will produce sounds as low as 20 Hz, but it’s essential to look at the frequency range to get a good idea of how the subwoofer will fit into the stereo system as a whole.


When looking at the specs of popular subwoofers, look at the sensitivity. This indicates how much power is needed to produce a particular sound. The higher the sensitivity, the less power a subwoofer will need to produce the same low-pitched sound as a speaker at the same level.

Enclosure type

Enclosed subwoofers that are already built into a subwoofer box will tend to give you deeper, fuller sounds than those that aren’t enclosed. Ported enclosures are better for louder sounds, but not necessarily deeper tones.


Measured in Ohms, impedance relates to a device's resistance to the audio source’s current being pushed through. Most subwoofers have 4 Ohms of impedance, but you can also find 2-Ohm and 8-Ohm subwoofers.

Voice coils

Most subwoofers come with single voice coils, but truly experienced or enthusiastic audio junkies often opt for dual voice coil subwoofers. With two voice coils, you’re able to wire the sound system as you see fit.


When choosing the best subwoofer, be sure to check out the power rating. In subwoofers, the RMS power rating is more important than the peak power ratings. This is because it measures the continuous power as opposed to peak power. If you have an amplifier already, make sure the subwoofer you’re looking at can handle that power output.

How to choose the best subwoofer

Subwoofers for cars

Have you ever pulled up to a red light and felt a deep vibration shaking your car? Somebody in the car next to you likely has a pretty great subwoofer powering the bass in the blaring music.

Subwoofers are particularly popular as part of a car audio system. Sonic Electronix sells car stereo subwoofers that are usually classified by size (8”, 10”, 12”, etc.) with the lowest frequency getting down to about 20-22 Hz.

How do you choose between an 8-inch subwoofer, a 10-inch subwoofer, and a 12-inch subwoofer? Well, it helps to start by analyzing the sound system currently in your car. Most cars come with factory-installed subwoofers as part of the sound system. However, those subwoofers are usually too small to handle the lowest frequency sounds a really good subwoofer might handle.

Then, it helps to figure out what you’re looking for out of the subwoofer. Things like dual voice coils, enclosure type, and impedance are all factors to consider as they affect the overall sound and compatibility with the amplifier and other speakers you currently have in the car.

Really, what you’ll want to look at are the types of subwoofers.

Component subwoofer 

This is just the speaker, which means you’ll still need to install it in a subwoofer box and power it with an external amplifier. Component subwoofers are great for customizable sound systems as they come in a variety of sizes and with a variety of features (impedance, voice coils, etc.).

Enclosed subwoofer

As the name suggests, these subwoofers are enclosed in the box already. While this is more convenient, it limits the number of choices you have in terms of customization. Similar to the component subwoofer, though, you’ll still need to purchase a separate amplifier.

Powered subwoofer

We talked about these earlier. Remember? Powered subwoofers are active in that they have an internal amplifier that means there’s less wiring involved in the installation. Because of this, they’re pretty compact and make a great addition to a car stereo system that just needs a little extra bass boost.

Subwoofers for cars

Subwoofers for home theater systems

The biggest difference between subwoofers for cars and subwoofers for home theater systems is the size. SVS home theater sound systems come complete with SVS subwoofers ranging from 12-inches all the way up to 16-inches.

The SVS SB-2000 Pro is an elite subwoofer optimized for deep bass production, churning out vibrating sounds that’ll go deeper than even the 20Hz human hearing threshold. And, the PC-2000 Pro stands at 34-inches tall, offering a unique take on the traditional subwoofer box that most are accustomed to.

Is all of that necessary? It depends on your home theater, really. If you’re trying to set up a sound system in a larger room, one 12-inch subwoofer box isn’t likely to cut it. It’s best to opt for one with over 100 watts of power. And, if you can, place two subwoofers strategically around the room for the best sound and feel.

Subwoofers for home theaters

Choosing the right sound

Choosing the best subwoofer depends on your overall audio goals. Where will the subwoofer go and what kind of existing sound system will it be a part of? If you can answer those questions, then you’ll be in good shape.

From there, you’ll want to start exploring other audio options that will help you make your decision.

Have a favorite subwoofer or a recommendation for a specific speaker based on different needs (bands, home theaters, cars, etc.)? Make sure to let us know on Facebook or Twitter.

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