Subwoofers 101:
A Complete Guide to Understanding Subwoofers
Subwoofers: You've heard them everywhere, whether it's cruising down the freeway or deep in space at a movie theater, but you've also heard when they weren't there. So what is a subwoofer exactly?
What is a Subwoofer
A Subwoofer (often referred to as a Sub) is a reliable and efficient means of improving the sound of any speaker system. It extends the range of your speakers by producing low-frequency audio that smaller speakers cannot, giving you that bone-shaking bass we all know.
What Does a Subwoofer Do
A subwoofer is used to reproduce the lowest frequencies that other speakers in the system can't reach at full volume. In the most general application, the subwoofer will work with a pair of smaller speakers to produce the bass that the smaller drivers are not capable of reproducing faithfully. While some media may not contain much low bass information, many types of rock, hip-hop, jazz, classical, or electronica rely heavily on low frequency content. In these cases, using a subwoofer will help fill out the sound and produce a more realistic experience. In home theater systems, there is a specific channel of sound specifically designed for the subwoofer, including most bass effects such as explosions, gunshots, and rumbles. Most home theater processors also contain settings to divert all low frequency content to the subwoofer, which frees the satellite speakers to play much louder and with less distortion.
What's the Difference Between a Woofer and Subwoofer
These terms have become almost interchangeable, and there is definitely a gray area between the two. The difference can be in the woofer itself, or how the woofer is being used. A raw speaker or "driver" that we call a subwoofer generally has a limited frequency response range, often not extending above about 400 Hz. A standard "woofer" can have frequency response easily reaching 2500 Hz or higher. This upper limit is a function of electrical and mechanical characteristics; often the large voice coil inductances on high-excursion subwoofers limit their high-frequency capabilities. It is a matter of compromise in the design of the woofer: trying to achieve good high frequency performance generally will cause poor low frequency and power handling abilities, while producing a powerful subwoofer with ultra-low frequency abilities and high-power handling will not be able to play well at higher frequencies. However, if a wider-range woofer is used only below 80 Hz or so it could be called a subwoofer due to how it is being implemented.
How Do Subwoofers Work
A Subwoofer comprises two main components; the Woofer and the Cabinet. The woofer moves back and forth to generate a wave of air at specific frequencies. The cabinet affects the rear wave of this swing to take advantage of the full swing of the woofer (more on this in a moment). After some time, the wave is picked up by your ear and interpreted as a note in a funky bass line or maybe the roar of an engine.
The Woofer
The woofer is the main component that makes the low-frequency audio. Woofers come in various sizes, but here, bigger is better. Anywhere from 8 to 21 inches, to be specific. It is made up of a magnet surrounding a winding wire called a voice coil, then attached to a cone. A current of electricity passes through the voice coil, which interacts with the magnetic field to drive the cone back and forth to push the air surrounding it. This is only half the magic behind a subwoofer.
The Cabinet
The cabinet looks like a big box, which is what it is, more or less. A big box with an important job; managing the soundwave that emanates behind the woofer. There are many types and sizes of cabinets to choose from, but you'll likely find similarities between different designs.
The dimensions and design of the box will depend on some characteristics of the woofer and the designer's ultimate goal, but that is outside the scope of this article (kind of).
Need Some More Help?
If you are looking for some more help with your subwoofer we have some resources. We have a guide to troubleshoot issues that you could have with your sub as well as a guide for selecting the best subwoofer for any DIY build.
A Fork in the Road...A Utensil Drawer
You still have a few choices to make after deciding you cannot live without a subwoofer, ported or sealed?
Sealed Subwoofers
A Sealed subwoofer is a cabinet with a completely sealed interior that confines the rear soundwave inside. This confined wave cannot interact with the woofer's front soundwave, resulting in cleaner output. This type of cabinet is often compact, limiting its lowest range to frequencies in the mid-30s.
(CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=52702)
Ported Subwoofers
A Ported subwoofer is a cabinet with a resonating pipe in its interior -or port that leads to the box's exterior. This port works with the woofer to increase range and output. This type of cabinet lends itself well to reaching frequencies in the 20s and lower but rather large.
(By Image based on Bassreflex-Gehäuse_(enclosure).png created by User:Melancholie., CC BY-SA 3.0, https://en.wikipedia.org/w/index.php?curid=2745689)
Bass Shakers?
The bass shaker is a relatively new low-frequency component that has recently reared its head. Instead of creating sound waves through the air, it uses your furniture as a medium. Bass shakers are exemplary at reproducing the tactile effects of booming bass without the high volume but are best for experiencing the absolute lowest frequencies.
TLDR:
Ported subwoofers can generally reach lower frequencies than sealed subwoofers but at the expense of size and complexity.
Sealed subwoofers integrate better than ported subwoofers with most rooms but at the expense of the lowest frequencies.
Bass shakers are the cherry on top but won't completely replace a subwoofer.
Now what?
Where Can You Use Subwoofers?
Subwoofers (and now bass shakers!) can be used pretty much anywhere you're expecting sound, from your home theater to your car, concerts, clubs, pretty much anywhere that needs to get loud.
Home Audio
If you are lucky enough to find a subwoofer in a home, it's likely for a home theater or hi-fi music system, typically both. Versatility is the name of the game here; you want it to get low when watching a movie and loud when you're jamming out. The ported sub is versatile enough for home audio and your safest choice if you can't decide.
Shop Home Audio
Car Audio
If you spend a lot of time driving around, you've probably considered getting a subwoofer for your car. There are a few schools of discipline regarding priority, High output, or overall quality. Bassheads looking for high output will want to get a ported subwoofer or its cousin, the bandpass subwoofer. Audiophiles will reach for the sealed subwoofer, taking advantage of the natural gain of the car to extend its lowest range and decrease distortion.
Shop Car Audio
Pro Audio
If you are here looking for the best subwoofer for your band, you're going to be doing some heavy lifting. There are many designs to choose from; Bass reflex, Horn, Bandpass, Transmission Lines. There are too many details to dive into here, but a popular choice is the Bass reflex. It is similar to a ported subwoofer in its range but optimized for high output. Just what you need!
Shop Pro AudioWhat's the Catch?
Besides the obvious concerns with the size of the subwoofer, the next consideration is probably all around you; your room. Location is one of the most influential things on your sound next to turning the thing on!
Room Nodes
A room node occurs when soundwaves bounce off walls and into each other at specific frequencies. This is less noticeable at high frequencies, but at lower frequencies you can have seats in your room with absolutely no bass. You'll have to experiment with placement to find a location that gives you the best sound in your listening spot or around the whole room.
A Fix?
Subwoofer Systems will produce more bass when they are placed in a corner. Choose a corner that is close to the component area and place the sub at the front of the listening area.
If you need a little more control over the way your sub sounds, consider adding DSP and acoustic treatment.
Learn About Acoustic Treatment
Power
You'll need to give your subwoofer plenty of juice if you want it to work for you. A subwoofer will only work if you have an amplifier to drive the woofer inside. This has been simplified with the popularity of powered subwoofers or subwoofers with a built-in amplifier. If you are not using a powered subwoofer, make sure your subwoofer has an impedance above your amplifier's minimum impedance. The output wattage of the amplifier should be as close to your speaker's power limit as possible.
Subwoofer Amps
If you are using a passive subwoofer, you will need a sub amp in order to power your sub.
Shop Sub AmpsWhere Do You Go From Here...The Plug
With your newly acquired knowledge of subwoofers, you can make your next decision, confident that you are doing justice for your system. Visit our website at Parts-Express.com to see a few of our favorite subwoofers or purchase one of our subwoofer kits designed by our speaker experts!
Still want more? Head over to our TechTalk forums for more in-depth discussion on subwoofers and all things audio!
Additional Tools To Optimize Your Subwoofer
Dayton Audio's DSP-LF Low Frequency DSP Controller gives you the power to revolutionize your home theater or listening room's low-end dynamic using digital signal processing. Easily integrate the DSP-LF into an existing audio system and take control over your bass response all from your smart mobile device. In tandem with the free iWoofer, Android/iOS app, the DSP-LF puts you in control of your bass's sonic character, tailored perfectly for the sound you desire.
Learn More
How To Build Your Own Subwoofer
Building a Subwoofer
There are quite a few really good subwoofer systems on the market today that give excellent performance. for a price. We have seen home subwoofer systems at high end hi-fi shops sell for as much as $5000. While $5000 will certainly get you one heck of a home theater experience, most of these subs will contain less than $1000 in materials. Likewise, many $1000 subs have less than $250 in materials. With a few common tools, a weekend or two of your time, and some elbow grease, Parts Express can show you how to build a sub that will perform like the commercially available ones and save you money.
Shop DIY Subwoofer Kits
Learn From The Best
Parts Express is a leading supplier in raw drivers, speaker components, and resources for speaker builders. Whether you are a seasoned vet or someone looking to find a new hobby, Parts Express has the gear and resources you need to complete your next project. The large community of speaker builders on our Tech Talk forum allow you to learn from some of the best in the business. For more inspiration, check out the Project Gallery which showcases a variety of designs from the speaker building community.
Want a second or third opinion about your speaker cabinet design or other audio related problem? Post your question or comment on TechTalk, our Technical Discussion Board. Hundreds of technicians, engineers, and hobbyists, nationwide read and discuss electronics related questions each week. We welcome your participation!
