What Is A Subwoofer… And What Does A Crossover Do?
Last updated on January 8th, 2023 at 12:25 pm
What Is A Subwoofer?
A subwoofer is a speaker (or driver as it is sometimes called) that is dedicated to producing the low-end of the audio spectrum.
This is the bass, or “bottom end” that is very much a part of most popular music, and just doesn’t sound quite right with out it.
The sub-bass is the part of the sound that really makes the music sound, and feel, good. It’s a little harder to reproduce because low end has longer wavelengths that the higher mid-range and treble frequencies do.
Because of this, it takes a larger driver to create those longer wavelengths. The speaker has to move in and out farther to reproduce those frequencies.
What Does A Subwoofer Do?
A subwoofer makes louder only the frequencies in the lower end of the sound of your music. It only has the lower range of the music sent to it from the amplifier. (See “What Does A Crossover Do?” section for more info.)
The upper low end, mid-range and high end, treble frequencies are sent to the main stereo speakers. This is the part of the music that they are designed to handle.
And because these low frequencies are filtered out, by a crossover (more on that in a minute), they don’t go to your main full-range speakers at all.
So the subwoofer also takes a big load off of the main speakers in your stereo system, And it allows them to be much more efficient.
Where Would I Use A Subwoofer?
Subwoofers can be used in just about any situation. And you may already have one.
Subwoofers For Home Theater
Samsung Soundbar With Subwoofer
The speaker system that you have with your TV might include a subwoofer. If you have a soundbar under the TV and maybe a couple surround speakers, there might also be a larger speaker cabinet that has one speaker in it. That’s the subwoofer. When watching your favorite movies, action scenes, car chases, and blowin’ crap up just doesn’t sound the same without it.
Also available from: Samsung & BestBuy (non-affiliate)
Subwoofers For Your Computer
Klipsch ProMedia 2.1 Computer Speakers
You probably have a couple speakers sitting on your desk or computer table next to your monitor. And there may be a larger square shaped cabinet sitting on the floor next to your desk. That’s the subwoofer. Computer speakers are a great place to add a subwoofer. We spend time on video sites and maybe even have music playing while we’re on the computer. The subwoofer can really help fill out the sound in this situation.
Also available from Walmart
Subwoofers For Your Car Or SUV
Rockville SS8P Slim Under-Seat Car/Truck Subwoofer
Subwoofers do the same thing in a car stereo: they produce the low end (bass) part of the music. And we’ve all heard just how loud these can actually be. Cars or SUV’s that you can hear from blocks away. And they shake the ground when they drive by. Not all of us want quite that much bottom end.
But car subwoofers come in a wide variety of shapes, sizes, and designs. From the speaker by itself that has to be mounted somewhere, to larger cabinets that sit in the trunk or the back of an SUV. There’s under-the-seat designs that are out of sight and out of the way, as well as many others.
Also available from Walmart
Outdoor Subwoofers
Polk Audio Atrium Outdoor Subwoofer
You can even have a subwoofer outside. You read that right. Outdoor subwoofers have become very popular in the last few years. And there’s lots of good reasons why. When the weather is nice, where do we like to spend a lot of time? Outside on the patio or by the pool. Hanging out with family and friends, grilling, eating a great meal, etc. And you always want some tunes on when you’re outdoors.
A subwoofer will take your outside listening game to the next level. Chances are you may already have a couple outdoor speakers mounted in your patio area. Or even the rock-type speakers that blend into your landscaping. It’s not that hard to add a subwoofer to your outside system. There are several different types of outside subwoofer, so there is sure to be something to fit your needs. There are surface type like the Polk Audio unit above, which you just sit where ever you want it. Partial and full burial type, that you actually put in the ground are becoming popular as well. And even rock type outdoor subwoofers that are nearly undetectable.
Also available from: Polk Audio & B&H Photo (non-affiliate)
Take a look at Coolest 5 Outdoor Subwoofers
ALSO READ: Best Outdoor Subwoofer For Your Home, Pool, And Patio
The Coolest5.com article that will help you find the Best Outdoor Subwoofer.
What Does A Crossover Do?
What is a crossover? And why am I talking about crossovers in an article about subwoofers? Answer: If you are looking at adding a subwoofer to any of your audio system, crossover is a term you’re going to be running into. A lot!
Simply put, a crossover is an electronic device that splits up the audio spectrum into sections and send each section to the speaker best suited to reproduce it. In our situation with subwoofers, that would mean splitting the full range signal into two sections. One that goes to the speakers that contains all frequencies except the low or sub-bass. The other section is sent to the subwoofer. Typically this will be only the audio frequencies below 200 Hz or so.
Depending on your application you will want to check the specs of your subwoofer and make sure that the signal being sent to it is crossed over at the correct frequency. This will help it perform more efiiciently and give you the best sound.
What Is A Passive Crossover?
A passive crossover accepts the amplified signal sent from the amp and it crosses it over to the correct speaker. In other words, the crossover splits the audio signal into pieces. Each piece contains a range of frequencies – ie, high, mid, and lows.
For example, if you have two-way speaker cabinets, a tweeter and a woofer, it splits it into two sections. The highs, everything above around 2,500 Hz goes to the tweeter. The rest of the signal goes to the woofer.
Passive crossovers will be the type you are most likely to encounter with home and car stereos. And they are generally inside the speaker cabinet, so you’ll probably never see them.
Passive crossovers accept an amplified signal. They let you connect a wire directly from the amplifier outputs to the speaker.
Active crossovers are mainly used is high end system and large PA rigs. They accept the line level coming from a pre-amp, split the signal and send it to sperate amplifiers. I won’t be dealing with active crossovers in this article.
How To Connect A Subwoofer
cheapaudioman has a helpful video on How To Connect A Subwoofer.
Passive Subwoofers
Now back to our main topic: Subwoofers. They can also be classified as passive and active. Here again, we’ll concentrate mostly on Passive Subwoofers.
Passive subwoofers accept a powered signal from the amplifier. You will need to look at the subwoofers specs to be sure that it contains an internal crossover. It is safe to send a
full-range, amplified signal to this type of sub. It will let only the low range frequencies pass through to the speaker. TIP: this also called a Low-Pass Filter.
Some receivers will have a Subwoofer Output. If it it an amplified signal, just hook that up to you sub. You may also have an adjustable subwoofer output on your receiver. This will allow you to set the crossover frequency from the amp in the receiver. Be sure to check the specs for your sub and match this frequency on your Subwoofer Output to the top end of the sub’s frequency range.
There are also some subwoofers that accept a full-range amplified signal and cross it over. (See diagram) Keeping the low end there at the sub, and sending the rest of the signal, minus the bottom end, to the satellite speakers. For a good example of this see the TIC B50 Outdoor Subwoofer on the Coolest5.com “Best Outdoor Subwoofer” comparative review page. The advantage of this would be that you only have to have on amp to drive all of the speakers.
Active Subwoofers
Active subwoofers have an amplifier built-in. And they have to have power. That means they require two things: a pre-amp level signal from your receiver, and 110AC power (in the US) for the amplifier. In other words, they need to be plugged in.
Powered subwoofers have their advantages. If your receiver has a pre-amp level output, you can just run it to the subwoofer and be done with that part. This could also mean that you won’t have to buy a separate amplifier. But, the subwoofer will be a little more expensive because it contains an amp.
Another advantage to an active subwoofer is that the internal amp, the driver, the cabinet will all be designed to work together by the manufacturer. You will be pretty much guaranteed to have enough power to drive the sub efficiently.
One little note here: there are very few, if any, active outdoor subwoofers. Almost all outdoor subwoofers are passive and require a powered (amplified) signal. The electronic components of an amplifier are just too hard to keep dry and protected when they are left outside in the weather. Plus, with being constantly outside in the weather, you wouldn’t want to have to run a power line to the sub. That would be too hard to keep protected, and unsafe as well.
Where To Put A Subwoofer
Where to place a subwoofer is an important topic as well. You can put a subwoofer just about anywhere. Frequencies in the low and sub-low end of the audio spectrum are omnidirectional. In other words, you can’t tell where they are coming from. This makes the location of the subwoofer less important than the other speakers.
Subwoofer Placement – Home Theater/Stereo
You will want to try different setups and placements. Because the waveform of low frequencies are very long, there may be spots in the room or listening space that are bass heavy, and others that are thin. Experiment with different type of music, and watching some movies to determine the best place to put a subwoofer. This will also work when deciding where to put your outdoor subwoofer.
Here’s a couple examples of how placement will affect your subwoofer sound. If it is placed in a corner it will enhance the low end and make it sound louder. Also, how close to, or how far away from the wall behind it will affect how the low end sounds in the room. This is especially true with rear ported subwoofers.
Another factor to consider in where to place a subwoofer is cabling. You will want to make sure that you can conceal or hide any cable running to the sub so they are not a tripping hazard or unsightly. You may also be limited on the placement if the sub is active (or powered). It will have to be placed near a power outlet.
PRO TIP: To ensure the best performance for your subwoofer, set it on a solid surface. This lets the cabinet resonate the way it was designed to. Do not sit it on a cardboard box. A wood or metal box will act as a resonant chamber that will color or change the sound. Setting it on a shelf will de-couple the cabinet and it will decrease the low end performance. A hardwood or concrete floor is best.
Subwoofer Placement – Car/SUV/Van
Subwoofer placement is not as much of a factor in automobile stereos. There’s a couple different reasons for that. Car stereo subwoofers come in many different sizes and shapes. They are specifically designed to perform in the smaller space of an automobile interior. And most are designed to be installed in a specific place. Some get mounted in the trunk or other places. There are even subwoofers that just slip under the seat. So there may not be a lot of options on where to put it.
The second reason that subwoofer placement is not as important in automobiles is the limited space. If you have a sub cabinet that mounts in the trunk or the back end of an SUV, moving it a few inches or even a foot one way or the other is probably not going to make much difference. Again, car subwoofers are usually very specifically designed. There is a certain place they are meant to be mounted. There won’t be any options about where to place it. But this also eliminates a lot of the guesswork.
Conclusion
Subwoofers are a specialized and important part of any stereo or sound system. We’ve all experienced full-range sound in theaters, at concerts, and lots of other places. We know how much better everything sounds when there is that low-end that you can feel. And it is not hard to add that element to your stereo/home theater, your computer system or car stereo, and even your outdoor system.
There are some things you’ll have to know to get the best type of sub for your situation and to make sure it is wired up, installed, placed, and powered correctly. I have tried to cover all of those aspects in this article without diving into too much detail and getting lost in the weeds.
I hope you enjoy your new listening experience after adding a subwoofer. And I hope you enjoyed this article and found it helpful. If so, please share it on social media and with friends. Please send any further questions or any comments to me directly at info (@) coolest5.com.
Thanks for reading.