What does a subwoofer actually do? We asked an expert

In partnership with KEF

If you want to know more about subwoofers, you’re barking up the right tree. David Bosch, Senior Research & Development Engineer at high-end audio specialists KEF, is top dog when it comes to audiophile tech.

Put simply, he tells NME, “a subwoofer is a type of speaker – a speaker is any device that transforms an electrical signal that represents music into sound that you can hear. Since the ‘80s, ‘90s, with the onset of home theatre, a new term was coined: subwoofer.”

This new bit of wizardry emphasised “the lowest bit of sound; the lowest two octaves”, resulting in fuller and more satisfying bass. Things have come on a lot since then, and KEF are at the forefront of all things ‘woofer. They offer a whopping eight subwoofer models: Kube MIE subwoofers (four models in the range, currently 10 per cent off until January 6), KC62 subwoofer, KC92 subwoofer, T2 subwoofer and the Reference 8b subwoofer. They’ve got the right model for any budget, room size or system type.

Active subwoofers contain their own amplifiers, while passive ones connect to a separate sound system. We’ll focus on the former magic boxes in this feature, which make your favourite tunes sound even more special. Get practicing your bass face.

With speakers, bigger is better (but not always practical)

“A speaker has circular membranes that push air to produce the sound waves that reach your ears. To produce bass, you need to move a lot of air really quickly, which means you need a lot of area or a lot of displacement. The size of the speaker box is usually directly related to how well they reproduce bass. The bigger the box, the better it can reproduce bass. A tiny laptop speaker, for instance, doesn’t do bass really well.

“If you want to produce something that is as low as 20Hz, which is at the threshold of human hearing – in a movie it’s a deep rumble; in music, it’s the lowest kicks – you would need a really, really big speaker. That’s not really practical in most homes.”

Which is where the subwoofer comes in

“To make a smaller speaker reproduce really low bass, you add some technologies. Active subwoofers modify the signal to boost the bass artificially, so that a small speaker can move a lot of air. You put a lot of force into it, which means a lot of amplifier power. That’s essentially what makes a subwoofer.”

Here’s what you’ll hear (and feel!)

“With a subwoofer, you don’t just hear the lowest frequency content in your music and movie. It’s also felt by your internal organs. Sub-bass excites your body because the size of the wave is so big. We usually talk about feeling the music. When the bass moves you, it can be very exciting. When you listen to a live band, a rock band, with a kick drum that’s kicked really hard, you can feel it. That’s the magic of trying to reproduce the lowest sound in movies and music: it’s extremely physical.”

Good vibrations: why it feels so right

“With a subwoofer, there’s so much more nuance. We like bass: human brains are hard-wired to get really excited by anything that vibrates us. Music, by definition, is emotional, right?”

Try it out on this track

“One song that springs to mind, which I like a lot, is ‘Sola Sistim’ by Underworld. The moment you add a subwoofer to that song, you’re like, ‘Now you’re talking!’ Most of the interesting bits of the song actually happen in the bass and sub-bass. It’s quite a dirty, square-wave bass. The lowest portion is, like… grunty.”

Hear songs as the artists intended

“A good audio system should be able to reproduce whatever the artist’s intention was, whether it was live music (assuming it was well-recorded) or studio-produced. If the artist intended for there to be any bass in particular, then obviously you need an audio system that can reproduce these sounds. Otherwise, you’re missing out.”

Everything in its right place

“It matters immensely where you place the subwoofer. A room is essentially a box. When sound is produced by a speaker and it travels to the walls, a part of it is reflected – and sometimes it is reflected back and forth many times before it gets absorbed, eventually, by the surfaces. In some areas of the room, it will sound very loud; in other areas, it will sound very quiet.

“It’s a very complex topic and something that is being researched actively in the scientific community of acoustics. At the end of the day, it requires every person to spend quite a bit of time trying positions until they find what is best for their room – because every room is different.”

Turn the lights down and the ‘woofer up

“Sitting down to listen to music is not that common anymore. People don’t have a lot of time to do that. We usually listen to music as a secondary activity while we are running or cooking or driving – et cetera. But there’s a whole different experience in sitting down in the dark and shutting down the rest of your senses so that the listening can fully take over, and trying to feel yourself in that performance. It’s quite powerful.”

Visit uk.kef.com to explore their subwoofer range and…

• Book a demo with one of their authorised retail stores via the KEF website. It’s a personal listening experience that can be customised to each individual with bespoke advice for their particular set-up
• Find an authorised KEF retailer for guidance on which KEF model is right for you
• Discover more about the all-new KEF Music Gallery London, located on Great Portland Street in London. The Gallery is a welcoming hub and event space for music lovers to be fully immersed in an ultimate high-fidelity listening experience

* Promotional savings shown are on suggested retail prices

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