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What is a subwoofer, how does it work, and do you need one?

If you have just started your journey in the world of high-fidelity sound, you might wonder why it’s crucial to add a subwoofer to your audio system. After all, perhaps you just spent hundreds of dollars on professional bookshelf speakers, so why investing more and adding a subwoofer to your system?

By enhancing lower frequencies, a subwoofer adds depth and dimensionality to audio, bringing to life an immersive sound texture that’ll upgrade your listening experience, whether you’re an audiophile or want to improve your home theater system.

A common misconception is that subs are great only if you listen to heavy-bass music. The truth is that a subwoofer will enrich the sound dynamics and make it more compelling, creating a more accurate and engaging soundstage you’ll love regardless of the purpose of your sound system or the music genre you reproduce.

Let’s learn more about subwoofers, how they work, how to make the most of them, and what to look for when choosing one.

About the author

I’m an audio engineer and audiophile with over 10 years of experience in the music industry. I entered the world of subwoofers when I started mixing and mastering music for a living. I’ve been studying and researching the best audio systems for years to ensure that whatever comes out of my studio sounds perfect on all playback devices. To achieve ideal results, I’ve experimented with dozens of audio systems and subwoofers, trying to find the perfect balance between sound accuracy, depth, and vibrancy.

Klipsch Reference subwoofer
Image: Klipsch

What is a subwoofer?

Subwoofers are loudspeakers designed to reproduce lower frequencies, generally within the 20-200 Hz range. They can reproduce lower frequencies more accurately than regular speakers due to their large speaker drivers, which can move more air and are designed to faithfully bring to life bass sounds.

Subwoofers are used in conjunction with bookshelves, floorstanders, and other types of speakers to perfectly replicate sound across all frequencies.

Subwoofers can be found in home theaters, live venues, cars, and home sound systems, and their purpose is always to enrich and deepen the soundstage with powerful low frequencies.

How does a subwoofer work?

Due to their structure, standard speakers can’t reproduce lower frequencies as accurately as higher ones, which is why we need a loudspeaker explicitly designed for bass sounds. The larger woofer of a sub, which can be anywhere between 8 and 21 inches, ensures the lower side of the frequency spectrum is reproduced with accuracy and depth.

Just like standard speakers, subwoofers can be either active or passive. Active subwoofers require a power supply and have their own built-in amp, while passive subs must be connected to a power source (a receiver or an amplifier).

Subwoofer placement

A few months back, I wrote an article specifically about subwoofer placement, so if you want to find out more about the topic, you can check it out here.

KEF speakers with subwoofer
Image: KEF

In a nutshell, being lower frequencies omnidirectional, you should be able to place your sub anywhere in the room and get an excellent bass-frequency response. Lower sounds tend to propagate across the room in all directions, giving you that immersive, cinematic sound typical of a sound system with a subwoofer.

If you want to make the most of your sub and ensure the sound is at the highest level of accuracy, you can place your subwoofer in various places in the room and use songs you’re familiar with as a test.

If you’re not satisfied with the sound or want to enhance even more the lower spectrum, consider buying two subwoofers and placing them on opposite sides of your listening room.

Choosing a subwoofer

Here are some of the most important things to consider before buying a subwoofer:

1. Purpose

There are subtle differences between subwoofers optimized for home theaters and hi-fi audio systems you might want to take into account if you want to get the best listening experience.

Essentially, subs that work better in a home theater system have a broader frequency response, capable of reproducing the deep sounds typical of audio-visual content.

On the other hand, hi-fi subwoofers focus more on accuracy and balanced frequency, often with a narrower frequency range but better integration with the existing audio system, and EQ controls to blend the sound coming out from all speakers.

2. Frequency range

You should always look for subwoofers that can get at least as low as 50 Hz; the lower, the better. Normally, you’ll find subwoofers that can reach down to 25-35 Hz, which is more than enough for most purposes.

A subwoofer with these features will perfectly reproduce frequencies within the audible range, enhancing the characteristics of bass-heavy music genres such as hip-hop or techno.

3. Wattage

While peak power is not something you should worry about when choosing a subwoofer, the RMS (root mean square) power is an essential factor to consider if you want to achieve a transparent sound reproduction at high volumes.

RMS is the power handling capability of the subwoofer over an extended period of time: a high RMS power rating means the subwoofer can produce louder and deeper bass. An RMS wattage of 150 watts or higher is more than enough for most small/medium-size rooms.

4. Wired or wireless

We’re constantly surrounded by cables, so a great thing about a wireless sub is that you won’t need any to connect it to your sound system. Plus, you can move it freely without having to worry about stumbling on wires scattered across your room.

Sonos wireless subwoofer
Image: Sonos

However, wired subwoofers offer a more reliable connection and generally deliver better and more powerful audio.

5. Size

Depending on your room, you might want to take into account the size of your subwoofer. Since it’ll need to be placed somewhere on the floor, choosing one that doesn’t occupy plenty of space is always ideal, but also bear in mind that the sub’s size often has an impact on its ability to reproduce low-end frequencies.

6. Compatibility

Finally, make sure your sub is compatible with your existing gear. Some producers (like Sonos) tend to release gear compatible exclusively with their product range, so it’s always a good idea to read reviews or double-check with the producer before purchasing the sub, should you have any doubts.

Frequently asked questions

In this section, I will answer some frequently asked questions about subwoofers.

Is a subwoofer only for bass?

Yes, a subwoofer is designed to handle exclusively lower frequencies, specifically, the ones between the 20-200 Hz range.

A subwoofer works together with standard speakers to deliver an accurate, full-range sonic experience, with the latter focusing on mid and high frequencies.

Can I use a subwoofer as a speaker?

No, you can’t. A subwoofer is designed to reproduce only low frequencies, and as such, it has to work together with a set of floorstanding, bookshelf, or other speakers to deliver accurate sonic reproduction.

Does a subwoofer need an amp?

Active subwoofers have a built-in amplifier that only requires a power source to function. On the other hand, passive subwoofers do require an amplifier or receiver to work.

How many subwoofers do I need?

In most cases, one subwoofer is enough to satisfy the needs of a home theater and audio system.

However, when placed opposite each other, two subwoofers can further enrich the depth of the soundstage, especially in a medium/large listening room.

Does a soundbar need a subwoofer?

A soundbar doesn’t need a subwoofer, but adding one would definitely improve the audio quality of your system.

Not all soundbars allow connecting external speakers or subwoofers, so ensure your model has this option before purchasing a sub. Although soundbars are designed to be an all-in-one solution for home theater systems, the sonic reproduction of a dedicated hi-fi system is often superior.

Final thoughts

I hope this guide helped clarify some of the most common doubts about the subwoofers. All in all, a sub is a crucial addition to your sound system if you want to achieve a pristine, immersive sound.

Nowadays, you can get exceptional results even with budget-friendly subs, so my suggestion is to just get one that fits your budget and needs and upgrade your sonic experience today.

Have fun!

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