There can be a lot of reasons why you would want to use a subwoofer without a box. Perhaps the most common is the desire to save trunk space when placing a subwoofer in your car. While this sounds like a dream come true, you might have to consider if it will truly work or not.
Subwoofers should not be used without a box as they require an enclosure to balance the front and back frequencies that are emitted. Using a subwoofer without a ported or sealed box can result in negligible sound.
In essence, the box is an essential component of how the subwoofer will emit the low-frequency bass tones that you are likely intending to play when you install a subwoofer in the first place.
Choosing to nix the box or another type of enclosure could result in minimal bass effect as the free-air concept would not quite work. However, there are still ways to rig your car to make this work, even with non-free-air subs. Continue reading to learn more.
Also read: Does a Subwoofer Need an Amp?
Why Should You Not Use a Subwoofer Without a Box?
Before you decide whether or not to attempt to set up your subwoofer without using a box, it can be important to understand why subwoofers need an enclosure in the first place.
Using this knowledge, you can then decide how to make an appropriate setup for your sub (either by purchasing free-air subwoofers or through rigging your own enclosure).
Subwoofers are designed with a few main components that work to emit low-frequency audio signals from the front and back of the speaker.
Without a sealed or ported enclosure, the frequencies that would typically be cast back into the enclosure are sent into the air freely and will likely cancel out the sound effect of signals sent forward.
In this way, the box (or enclosure) works to create the perfect setup for the low-frequency audio signals emitted by the subwoofer to follow the laws of physics in order to provide you with the deep bass that you are going for. Without a box, the subwoofer simply cannot perform in the same way that it was designed to.
However, there are a few different options for the type of box or enclosure that you will need to use with your subwoofer in order to achieve the deep bass in your car (or in another setting).
Specifically, you can use a ported or sealed enclosure, or you can manually modify your trunk to meet the needs that a physical enclosure would otherwise serve.
In essence, you can seal off your trunk so that it acts as the entire enclosure rather than having to place a box with your subwoofer setup.
This will save you loads of space as well as help you to maintain a strong aesthetic appeal with your vehicle, but it will of course take quite a bit of adjustment and modifications to make this work.
Even then, you may find that you are still not receiving the type of audio experience that you were originally hoping for.
Also read: Can a Woofer Be Used as a Subwoofer?
What Types of Enclosures Can You Use with a Subwoofer?
Now that we have addressed why there is a need for some type of enclosure for the subwoofer to perform as it was designed to do, you might be curious how you can make this work.
Specifically, if you are still wanting to use a subwoofer without a box, you are likely curious as to how you can design your setup to support the emission of low-frequency audio signals. First, let’s take a look at the types of standard enclosures before we make adjustments.
There are two main types of enclosures to use with a sub including sealed and ported enclosures. A sealed enclosure maintains an airtight seal around the sub allowing for crisp, detailed bass tones.
A ported enclosure has small vents that allow air to flow out when the subwoofer moves backward creating a booming (louder), though less clear effect.
These enclosures are specifically designed to be enjoyed by a variety of users. For example, you might find that the type of music you listen to requires a deep, clear bass to be able to fully appreciate this. Consider the deep bass of a cello that might play in classical or jazz music.
You would not want this sound to be muffled or displaced (like it would be in a ported enclosure for your sub). Instead, the best audio experience for listening to jazz or classical music would use a sealed enclosure for your subwoofer that allows the crisp, detailed bass tone to be carried out.
Then, you will be able to hear every note of the cello (or of another deep bass instrument) clearly as you enjoy your favorite song in this genre.
With a sealed enclosure on a subwoofer, you will not find any holes or vents as the airtight seal maintains the frequencies that are emitted when the sub moves backward.
Then, the signals that are sent forward (when the sub moves in this direction) complement the echoing effect that takes place in the sealed box.
Alternatively, ported enclosures have tiny holes or vents typically located at the bottom of the enclosure. These vents allow for air to pass through them.
So, as your sub moves forward and backward, the sub emits low-frequency audio signals as it moves forward, and then it emits them backward into the ported enclosure.
But, since there are tiny holes or vents in the ported enclosure, the sealed boom is not entirely contained in the box. Instead, some of this bass is sent through the air that flows through the ported vents.
In this way, a sub using a ported enclosure will sound louder or have more of a booming effect when it is used caused by the tiny echoes or bursts of air that are coming from the vents.
If you are listening to rock, rap, or another type of music that does not require the crisp, clear bass sounds that need to be distinguishable from one another to be enjoyed, then using a ported enclosure would be a great option.
The sound might not be as detailed, but the low bass emitted by your sub will be louder than what you would typically hear when using a sealed enclosure on your bass. So, if you are ready to jam out in your car, this might be the way to go.
If you are hoping to avoid using a box with your subwoofer, you will still need to create some type of setup that will allow the subwoofer to perform as it was designed to by casting low-frequency audio signals forward and backward as it moves in those directions.
So, in this case, you might be looking at creating a makeshift or a do-it-yourself enclosure for your sub.
A few options are available if you choose to go this route. First, you could choose to use your trunk as the “enclosure” by completely sealing off the cabin of your car.
This could take some serious work to ensure that there is no air escaping through the cabin- otherwise, this would almost be like a ported enclosure.
Instead, using the trunk as a “sealed” enclosure, you increase the likelihood that the audio signals sent by your sub will not be canceled in the free-air makeshift setup.
Another option is to design an enclosure that is specifically fit for the dimensions available in your car. While this might not be the typical route, designing an enclosure (sealed or ported) that can surround your sub while still fitting into a smaller space in your car can help you to achieve the best of both worlds here.
To do this, you would choose the best possible placement for your sub in your trunk (or in another location). Then, taking precise measurements, you could cut and design an enclosure that would fit around the sub while fitting like a puzzle piece into your trunk.
In this way, you eliminate the hefty amount of space that a typical box would take up. But, you still provide your sub with the proper equipment to be able to perform at its best.
Finally, you could choose to purchase free-air subwoofers that can install with ease in the trunk without the use of a box.
Since these are specifically designed to be used without a box, you will not have to make your own enclosure to make up for what is missing. Instead, the structural components of this type of sub are designed within its inner workings.
So, whether you choose to purchase a subwoofer that is specifically designed to be used without a box, or you choose to create or purchase an enclosure for your sub, just be sure that you make some type of safe and appropriate box that allows your sub to work as it was physically designed to do- with forward and backward movement encapsulated and emitted through the enclosed space and then to your ears.