Why do the speakers have a hole in the back?

Look through a list of speakers and you’ll quickly notice that many models – from large, bulky towers to sleek, modern bookshelf speakers – have holes in the back. Although sealed enclosures exist, variants with this opening seem to be much more common. Why is this so? Why do the speakers have a hole in the back?

In short, these holes are called ports. Think of them as tuned openings that allow air to flow in and out of the enclosure while the woofer operates, boosting low frequencies and helping your speakers achieve rich bass. Technically, a ported speaker enclosure is tuned to a specific resonant frequency where the bass response of a closed enclosure of similar size would decrease. By introducing a port, the speaker achieves a wider frequency response than the woofer would typically be able to produce on its own if the enclosure were fully sealed.

Although the position of the port affects the sound (especially how it plays with the air in your room), in most cases a ported design makes the speaker efficient and reduces distortion at higher volumes. If you compare it to a sealed speaker, you’ll see that a closed-back design can provide a tighter bass response, but it also requires a more powerful amp. This doesn’t mean that ported speakers are inherently better, just that they deliver punchier sound at similar power in smaller packages, so to speak.

The speaker ports may look like a typical audiophile woo-woo at first glance, but it’s actually pure physics. Each time the woofer comes out, air is pushed out of the port, and once it returns to its original position, the port draws air in again. That’s the bottom line: the speaker will gain a lot more punch with a lot less amp power and relatively underpowered speakers. And while many wonder why speakers have a hole specifically in the back, there are front-port speakers as well. The acoustic ports are a nice feature, but they can introduce excessive noise at high volumes. In most cases, this isn’t a problem because the extra noise blends into the bass. However, for optimal sound, speakers with rear ports should have at least two feet of clearance from the rear wall.

So, are ported speakers the ultimate solution to the speaker world? It’s really a matter of personal preference. There’s no shortage of audiophiles who swear that sealed drivers deliver more “realistic” bass sound. Whether they’re right or not, in general, ported speakers are just more user-friendly. That said, choosing the right amp size can be tricky in itself, as there are many variables to consider, including room size. A similar level of variability also extends to the question of ports versus no ports. For example, speakers with ports can give the sound more “body” at reasonable power. Sealed speakers are somewhat the opposite. If you plan to listen to genres that don’t rely heavily on bass, a sealed pair may end up sounding more musical to your ears, especially if you’re listening in a smaller room. So ultimately things are different for different people, just like most other audio related questions.