Subwoofer Facts for Kids

Subwoofer

A subwoofer is a special type of loudspeaker that plays very low sounds. These deep sounds are called "bass" or "low frequencies." Subwoofers are designed to produce sounds in a range like 20 to 200 Hz. This is much lower than the sounds most regular speakers make.

Subwoofers are usually quite big and heavy. This is because making very low sounds needs a lot of air to move. A larger speaker cone and a strong box help create those powerful bass vibrations. While humans usually can't hear sounds below 20 Hz, if the sound is strong enough, you might not hear it, but you can definitely feel it as vibrations!

What Does a Subwoofer Do?
- Why Are Low Sounds Important?
Where Are Subwoofers Used?
How Subwoofers Work
- Speaker Drivers and Enclosures
- Active vs. Passive Subwoofers
Images for kids
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What Does a Subwoofer Do?

A subwoofer's main job is to add depth and power to sound. It handles the lowest notes in music, like the bass guitar or kick drum. In movies, subwoofers make explosions and rumbling sounds feel more real. Without a subwoofer, these low sounds might be weak or even missing from what you hear.

Why Are Low Sounds Important?

Low sounds, or bass, are a big part of how we experience music and movies. They add excitement and realism. Imagine watching an action movie without feeling the rumble of a car chase or the boom of an explosion. Subwoofers make sure you don't just hear these sounds, but you also feel them.

Where Are Subwoofers Used?

Subwoofers are found in many places where great sound is important.

Home Theaters: Many people use subwoofers with their TVs to make movies and video games sound amazing.
Car Audio: Car enthusiasts often add subwoofers to their cars for a powerful music experience while driving.
Concerts and Events: Large subwoofers are used at concerts, festivals, and clubs to make sure everyone can feel the music's beat.
Computer Speakers: Some computer speaker systems include a small subwoofer to improve sound for games and music.

How Subwoofers Work

Like other speakers, subwoofers work by vibrating a cone to create sound waves. However, subwoofers have larger cones and stronger magnets to move more air. This helps them create those deep, low-frequency sounds.

Speaker Drivers and Enclosures

The main part of a subwoofer that makes sound is called a "driver." This is the cone that moves back and forth. The driver is usually placed inside a special box called an "enclosure." The enclosure is very important because it helps direct the sound waves and stops them from canceling each other out. Without a good enclosure, the sound from the back of the driver would mix with the sound from the front, making the bass sound weak.

Active vs. Passive Subwoofers

There are two main types of subwoofers:

Active Subwoofers: These are the most common type. They have a built-in power amplifier inside their enclosure. This means you just plug them into a power outlet and connect them to your sound system. The amplifier helps make the bass sound strong and clear.
Passive Subwoofers: These subwoofers do not have a built-in amplifier. They need to be connected to a separate amplifier, just like regular speakers. Passive subwoofers are often used in custom sound systems where people want to choose their own amplifier.

Images for kids

12" (30cm) subwoofer driver. A driver is commonly installed in an enclosure (often a wooden cabinet) to prevent the sound waves coming off the back to cancel out the sound waves being generated from the front of the subwoofer.
View of the underside of the downward-firing Infinity Servo Statik 1, showing the size of the 18-inch (45cm) custom-wound Cerwin Vega driver in relation to a can of Diet Coke, to show scale.
A display of Cerwin-Vega speaker enclosures at the 1975 Audio Engineering Society meeting.
Heavily braced and built subwoofer enclosure.
A large subwoofer cabinet used in a home hi-fi system.
This picture of the internal components of an active (powered) subwoofer shows the circuitry for the power amplifier.
This rear panel of a powered subwoofer shows the heat sinks used to cool the power amplifier.
This picture of the rear panel of a Polk subwoofer cabinet shows a low-pass filter adjustment knob.
The rear panel of a down-firing, active subwoofer cabinet.
The 1987 Bose Acoustimass 5 stereo bass driver contained one six-inch (152 mm) driver per channel and provided crossover filtering for its two cube speaker arrays
A small subwoofer cabinet designed for use with a home computer.
Multiple subwoofers in a car hatchback
A homemade car audio subwoofer speaker box with a 15-inch Boss Audio subwoofer and an empty space for a second driver
Each stack of speakers in this sound reinforcement setup consists of two EAW SB1000 slanted baffle subwoofers (each contains two 18" drivers) and two EAW KF850 full range cabinets for the mid and high frequencies.
A row of subwoofer cabinets in front of the stage of a rock concert. One enclosure out of every three is turned backward to make a cardioid output pattern.
Large subwoofer enclosures.
Cardioid dispersion pattern of two end-fire subwoofers placed one in front of the other. The signal feeding the enclosure nearest the listener is delayed by a few milliseconds.
CSA: Six subwoofers arranged for less bass energy on stage. Signal going to the reversed enclosures is delayed a few milliseconds.
End-fire array using three rows of subwoofers. Each row is delayed a few milliseconds more than the previous row.
Bass reflex enclosure schematic (cross-section).