Sealed vs Ported vs Bandpass Subwoofer Enclosures — What’s The Difference?

If you’re buying a subwoofer, there are probably two things on your mind. How do I get deep bass? And how can I get loud bass?

Subwoofers are excellent aftermarket additions to your car sound system. They can handle low frequencies your OEM (original manufacturer speakers) simply can’t produce without considerable distortion.

But nobody wants half-hearted bass. Without an enclosure, you’ll be losing out on a huge majority of the power your sub can handle. The result? Meek bass that doesn’t blow anybody’s mind.

Subwoofer enclosures can seem complicated – there are sealed enclosures, ported (also known as vented) enclosures, and hybrid bandpass enclosures. And then there’s the possibility of free air subs to discuss.

And choosing the right box for your subwoofer can make a difference to volume, depth, and quality of sound as well as the space it requires in your vehicle.

So let’s get deep into the world of subwoofer enclosures.

Why Do Subwoofers Need A Box?

Subwoofers produce the deepest and loudest bass when they’re enclosed in a custom box that stops the sound from the rear cone from hitting the sound from the front and canceling each other out. All enclosures separate the front of the sub from the rear – but they do it with differing constructions that trap air or allow it to move in different ways.

An enclosure doesn’t just improve the sound of your sub either – it can also protect it from damage by containing the driver’s vibrations. When you’re shopping for a top rated car audio subwoofer, you’ll have to consider the right enclosure.

Sealed vs Ported vs Bandpass: What’s The Difference?

Subwoofer boxes are found in three common configurations – sealed, ported, and bandpass. So what’s the difference?

Sealed Enclosures: For Tight And Accurate Sound

Sealed boxes are extremely common in subwoofer and speaker box design. As the name suggests, these enclosures are sealed so that no air can escape from the box built around the back of the sub.

Sealed boxes effectively separate the front and rear of the subwoofer, and the wave from the rear of the cone can’t affect the output of the subwoofer. The air pressure in the enclosure is changing constantly as the driver moves, acting as a spring to keep the cone of the subwoofer in the right place. This means that sealed enclosures produce exceptionally tight and accurate sound.

However, because of the forces in the internal, sealed enclosure, the amplifier has to work harder to power the sub – overcoming these forces in the process. That means sealed enclosures are less efficient when it comes to power.

Lastly, sealed subs can be built smaller than ported subs because they require less space. The smallest sealed subs will have a super tight, smooth response but limited production at the lowest frequencies, while larger sealed subs have a deeper bass response, but can’t handle as much power because the movement in the box can damage the cone.

Ported, aka Vented Enclosures: For Bass That Packs A Punch

Ported subwoofer enclosures differ from sealed enclosures because ports, or vents, allow air to escape from the internal space around the rear of the subwoofer.

These vents allow sound waves to escape the rear of the subwoofer and couple with the sound from the front – effectively increasing the output of your subwoofer. That’s why ported enclosures are more powerful, and louder, than sealed subwoofers.

Ported enclosures are much harder to build than sealed enclosures because if the vents are arranged incorrectly, air will move too quickly into, and out of, the enclosure risking damage to the sub itself. And the sound waves from the front and rear of the subwoofer won’t be aligned, so the sound from a ported enclosure won’t be as tight.

Ported enclosures are almost always roomier than sealed subwoofer enclosures – and the volume of air contained in the enclosure will have a dramatic effect on the durability and performance of your sub.

Bandpass: For Deep Bass That’s Extra Loud

Bandpass boxes are a hybrid enclosure, functionally providing the best of both sealed and ported enclosures. Naturally, they’re more challenging to build and more expensive to buy.

Bandpass enclosures divide the total box into two chambers, one of which is sealed while the other is vented. This makes them able to operate efficiently with a high power output while also offering a great deep bass response with little distortion.

However, the output of a bandpass enclosure will depend heavily on its construction. If the sealed compartment is smaller, deeper bass will be the most efficient, but some frequencies will play louder than others – excellent if you’re after deep bass. Meanwhile, a larger volume of air in the sealed chamber will provide a smoother frequency response. Generally, a bandpass box won’t provide as smooth a bass as either sealed or bandpass, because they prioritize certain frequencies.

Another benefit of the bandpass enclosure in car audio is that through the porting you can direct the sound into the cab. If you’re installing a subwoofer behind steel seats, for example, this will dramatically boost the quality of your audio.

Free Air: Convenient But Underpowered

Some subwoofers can be mounted without an enclosure – known as free air. Free air subs are built with a reinforced rear deck and a stiffer basket to facilitate sound quality without an enclosure, but they’ll usually be a lot less punchy and booming.

What Are The Best Enclosures For Deep Bass?

All of the best subwoofer boxes will hit the low frequencies well, but a bandpass box with a smaller sealed chamber will put a premium on the lowest frequencies, playing them loud and proud.

Final Thoughts…

Don’t get boxed in thinking about subwoofer enclosures. Finding the right enclosure for your sub will give you the bass you want, whether that’s tight and accurate, super deep or just plain LOUD.

Most subwoofers are versatile and can be enclosed in either sealed, boxed or bandpass enclosures – but free air subs are built differently. The space you have for installation will be another consideration when you choose an enclosure.

Whatever you choose, an aftermarket subwoofer is an essential component in your sound system. It’s time to feel the bass.

Robert Muñoz

I’m Robert, a US-based auto electrician, auto mechanic, trained engineer and fanatic about all things motor vehicle. After studying engineering in college I returned to my original passion - car mechanics - and I ran a garage for a number of years serving my local community. Through my garage, I got involved in numerous road safety campaigns in my local area until eventually, I decided to share what I've learned with the world. Know more about me... You can follow me on LinkedIn.

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