What Does a Car Subwoofer Do?

Ever wondered what the point of a subwoofer is in a car? Wonder no more! (Hint: it’s all about that bass.)
Written by Cameron Thiessen
Reviewed by Amy Bobinger
Not all cars come with dedicated subwoofers—subwoofers are audio speakers dedicated to lower frequencies. A subwoofer will improve the audio quality and allow you to pump the volume—and the bass—louder without distorting the sound.
If you love listening to music on your car stereo system but find that the sound quality is compromised at high volumes, you might be in the market for a subwoofer! Low frequencies are the most difficult sounds for regular car speakers to process. If you try to pump the bass too loud through them, these low-frequency sounds can overpower the speaker, distorting the overall sound quality.
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What is a car subwoofer, and what does it do?

A subwoofer is a speaker dedicated to pumping out low frequencies—sometimes referred to as “sub-bass” frequencies—to allow for more clarity in the overall mix. Ultimately, this should result in a more “realistic” sound and an overall improved listening experience.
There are various types of speakers that can be used to reproduce sound for an audio system. The main elements of a speaker system are usually tweeters, midrange speakers, woofers, and subwoofers. A car’s stock speakers will usually have tweeters, midrange, and woofers, and they’ll be able to comfortably reproduce frequencies above the 80 Hertz range. A subwoofer is used to reproduce the 20 to 200 Hz frequency range.

How a subwoofer can improve your car audio 

A subwoofer improves your audio by reproducing a full range of bass frequencies, taking the load off of your smaller speakers. This will achieve a better bass response and a fuller sound overall, with far more clarity and less distortion.
Most deep bass sounds—including kick drums, bass guitars, bass synthesizers, and low voices—sit around the 16 to 60 Hz sub-bass range. That doesn’t mean you won’t hear them at all if you don’t have subwoofers. All of these instruments still produce sound that has harmonic frequencies in the range that your woofers can handle, but you won’t get the fullness of those sounds as they were originally recorded or mixed.
A good way to imagine this difference is to think about how bass “hits you” when you’re listening to it in a club with big speakers versus when you’re listening on a little bluetooth speaker. You might still hear some of the bass sounds on the little speaker, but you’re only hearing the higher bass and mid-range frequencies they produce. When you’re in the club or in a car with a subwoofer, you can hear a much broader range of those frequencies, and the bass sounds much fuller as a result.
The reason you can “feel” bass like this is because speakers reproduce sound by pushing and pulling at the air in front of them. Bass frequencies are longer sound waves (lower Hertz) that require the movement of more air to reproduce them. This means a subwoofer enclosure needs to be bigger than your higher frequency speakers. 

Types of car subwoofers

All subwoofers fit under one of two categories: passive and active (or powered). Within these two categories, you’ll have to decide on the size and type of enclosure, the size of the woofer, its RMS power rating, sensitivity, and impedance, and the number of voice coils it has.

Passive vs. powered subwoofers

Any subwoofer needs to be connected to a sub amplifier. Powered subwoofers have a built-in amp, while a passive subwoofer needs a separate external amplifier component. If you’re looking for a simple, affordable subwoofer system setup, powered is the way to go. However, a properly arranged passive subwoofer system will be more versatile, so it might be your best choice if you want top-level sound quality.

Enclosure

The enclosure is the box that the subwoofer speaker is mounted into. Some subwoofers will come pre-mounted into a standard enclosure—these are called enclosed subs. However, if you want a custom fit, you might prefer to buy or build an enclosure and install a subwoofer speaker component into it.

Size

When deciding on the size of your subwoofer, consider the type of music you’ll be listening to and how you want your bass to sound. A smaller subwoofer—like an 8-inch or 10-inch sub—will have quicker response, allowing for clearer, punchier bass. However, a bigger subwoofer—we’re talking 15 inches—will produce boomier, fuller bass. Generally 12 inches is the sweet spot. Also, bear in mind that a bigger subwoofer will be able to produce louder sound than a smaller one.

Power

If you’re using a separate amp and subwoofer, it's important to make sure that the RMS power rating matches between them. However, you also need to make sure that your power specs match your car audio system’s head unit. You want to use a subwoofer that won’t draw more power than your amps can put out.

Sensitivity

The sensitivity of your subwoofer refers to the amount of volume—measured in decibels—it will put out with 1 watt of power. However, as you apply more power, the output will only go up 3dB per watt. This is why there’s an advantage to having multiple voice coils.

Impedance and number of voice coils

Your amplifier is the part of the puzzle that pushes the voice coil in the subwoofer to produce sound. The voice coil meets the power delivered by the amp with electrical resistance, otherwise known as impedance, measured in Ohms. The lower the impedance, the less power the amplifier will have to put out. 
Car subwoofers have either one single voice coil (SVC) or a dual voice coil (DVC) setup. A DVC sub will be able to produce twice the volume, as it allows you to optimize the power output of your amplifier.

Benefits of adding a car subwoofer

Adding a subwoofer to your car audio system will allow you to listen to high-quality audio with low bass frequencies in your car at louder volumes without overpowering your stock speakers.

How much does a car subwoofer cost?

Price can vary greatly between subwoofer setups, since there are so many different options available. Generally speaking, adding a subwoofer to your car will cost anywhere between $50 and $1000.

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FAQs

Technically, no. It's an amplifier that will make the sound louder as you increase its power output. The subwoofer itself will improve the clarity and realism of the sound by reproducing low frequencies that regular speakers struggle to reproduce.
The worst thing that a subwoofer can do is it might drain your battery faster. It is possible for a poorly-installed subwoofer to cause rattling, which might lead to some components shifting or loosening. It’s also technically possible that a subwoofer at extremely high volumes can cause windows to shatter, but this is extremely rare, and shouldn’t happen unless you install your system so that the subwoofer is blasting directly at a window.
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