KEF KC92

Just as it has with wireless ‘system in speakers’ set-ups (such as the excellent LS series), so KEF has the concept of ‘big bass from tiny subwoofers’ pretty well mastered – and not only sheer bass weight, but tight, controllable, extended low frequencies just as well suited to enhancing your music as shaking the room with action movie soundtracks.

Its latest arrival, the KC92, is not as compact as the football-sized KC62 launched a while back, but it’s hardly massive. It’s a near-cube, just over 36cm deep, a little more than 35cm tall and 33cm wide - so it’s going to slot in almost anywhere in even the smallest rooms, and is finished in gloss black or white to keep the domestic harmony going. And while the dimensions suggest it might be the ideal partner for a LS50 Wireless II speaker set-up – there’s even an optional cable-free transmitter/receiver for the sub – the appeal of this diminutive powerhouse goes a lot further than that.

Back in the dim and distant, when powered subwoofers first prowled the earth, I stumbled across them as an add-on for surround systems - these were the days when Dolby Pro-Logic was the thing and a 5.1-channel set-up was as much as anyone would countenance having in their listening room. We all went a bit bonkers with subs in those days: if they couldn’t make your sofa vibrate, rattle the china flying ducks on the wall and threaten to rearrange your internal organs, they weren’t worth having - and for a while I ran a subwoofer the size of a decent chest of drawers in my system

When I grew up, I realised that subs were even more effective as a means of making more of my music: schooled by a passionate fan of classical music and advocate of full-range listening, I dialled down the room-shaking and sank further into realistic sound, which is where this latest KEF comes back into the story. Yes, it can do the bangs and crashes with the best of them – but even the worst subwoofer can make a reasonable fist of that – but where the KC92 really scores is in its ability to integrate smoothly with speakers from small standmounts to large floorstanders, significantly extending their capabilities. Take a look at the KEF website, and you’ll see a ‘serving suggestion’ using a pair of the company’s Blade speakers, each one partnered with a trio of subwoofers (yes, really!) used together with the company’s optional stacking kit.

The KC92’s styling matches that of the latest KEF wireless speakers, but the appeal and capabilities of this subwoofer are much wider. It has both preamp-level inputs and connections at speaker level, the latter via the Euroblock multicore connector provided in the box, and more than enough scope for adjustment to accommodate just about any speaker pairing or room position. What’s more, the fundamentals of the design are all about clean, controlled low-end extension without any of the common flaws found in subwoofer design.

For a start, there’s the drive unit/amplifier combination: rather than a single big woofer in a ported cabinet, prone to flapping and tricky to control, KEF uses a pair of 23cm drivers mounted on opposite sides of the sealed enclosure, in what the company calls a ‘force-cancelling’ configuration. In other words, the vibrations from one driver are cancelled out by those from the other. The drivers use an aluminium-over-paper cone construction for speed and extension without weight, while the pleated ‘P-Flex’ surround, apparently inspired by origami techniques, is there to allow the driver to move more accurately.

Driving all of this is a pair of 500W Class D amplifiers – one for each driver – chosen for their efficiency, accuracy and cool running, and fed from a suite of KEF technologies to enhance performance. The proprietary ‘Music Integrity Engine’, running digital signal processing, is a series of algorithms designed to optimise the working together of all the systems in the KC92, while ‘Intelligent Bass Extension’ analyses the incoming signal and adjusts for consistent performance at any listening level.

Meanwhile, controls are provided to set the level and the crossover frequency (i.e. the upper frequency point at which the subwoofer is rolled off, handing over to your main speakers), and there’s a five-position selector to tune the KC92 for various positions within the room. There’s a signal-sensing power on/standby, allowing the subwoofer to ‘wake up’ when a music signal is detected, then go back to sleep a short time after the entertainment ends. It works well, and could come in handy if you need to place the sub in an inaccessible position in the room.

And where will it fit in your room? KEF even provides a handy AR visualisation tool on its website: load it onto your phone using a QR code, and you can move a virtual KC92 around until you find somewhere that suits.

Sound quality

I spent a relatively short time with the KC92 plumbed into my surround sound system, for a couple of reasons. First, as already explained, it doesn’t take much of a subwoofer to deliver all that over-the-top ‘slam and blam’ stuff (of which I’m not exactly a fan anyway), and second, of late any movie watching has been taking a back seat to music listening. And the KC92 – while more than up to the task of giving a good impression of that A-bomb test in Christopher Nolan’s Oppenheimer, or punching out the aerial combat of Masters of the Air, played on a reasonable surround system – is ideally suited to the subtler demands of making music just that bit more real.

Whether used with my desktop system, using a NaimUniti and Neat Iota speakers, or a main set-up employing the HiFi Rose RA280 amp and a pair of PMC Prodigy 5s, the KC92 does that clever subwoofer trick of not only filling in the low bass – yes, even with the substantial-sounding ‘big system’ – but also subjectively bringing out the qualities of the speakers used as the main pair. It’s something I’ve noted in the past (it also works when supertweeters are employed to deliver ultra-high frequencies above the capabilities of the main speakers, but that’s a story for another day) - and it’s something at which the tight, clean bass of the KC92 seems particularly adept.

The claim is that it can take your system’s bass right down to 11Hz – try it with a recording of a huge cathedral organ and it doesn’t seem fanciful – but more to the point is that it seems capable of making almost any stereo speaker system just sound more real. Even with solo piano, the added sense of the weight of the instrument has a magical effect, while with more obvious candidates, such as rock or dance music, the extra low-end power is addictive.

True, with the sub set up so it ‘disappears’ into the whole sound of a set-up, it’s all too easy to accept this new-found realism for granted, and begin to wonder what the KC92 is bringing to the party. The answer is to simply turn it off for a while, and discover in very short order just what you’re missing.   

Living with

The simple fact is that, while the KEF sub is far from bargain-basement, what it brings to the sound of a system is made even more impressive by its flexibility, and the ease with which it can be set up to deliver its best performance. Connect it via interconnects, from your amp’s speaker outputs, or even using the optional wireless package (an extra £200), set up the various parameters on the control panel, and adjust the level until you can just hear what the subwoofer is producing. Then turn it down a shade until it ‘vanishes’, and you’re all set!

Conclusion

There’s no shortage of subwoofers out there, from budget options to massive ground-shakers probably best reserved for huge dedicated cinema rooms - but the KC92 strikes just the right balance between power and subtlety, giving it near-universal appeal. Yes, it’s clearly designed to complement KEF’s own speakers, but it’s even more impressive when combined with set-ups where logic suggests it may not have anything to add, where it will defy expectations in (non)spectacular style.

Listening notes

Beyoncé Texas Hold ’Em

From the box of delights that is the epic Cowboy Carter, this track’s lush production and driving beat open up with the KEF sub in harness, delivering just the right combination of good-time twang and low-end power

Béla Fleck Rhapsody in Blue(s)

Bluegrass banjo maestro Fleck’s reinterpretations of Gershwin are fresh and fascinating, and this little piece, featuring long-time associate Victor Wooten on grumbling bass, really shines with a little active low-frequency assistance

Vampire Weekend Connect

If more proof were needed that subs aren’t just for explosions and pounding beats, here the KC92 helps deliver the sometime chaotic mix of a track from the Only God Was Above Us album, full of fits and starts, rippling keyboards and stabs of high-speed percussion

Tucked away somewhere unobtrusive, the KC92 will make anything from mini-monitors to large floorstanding speakers sound bigger, richer, more open and much more expensive. Beautifully built and cleverly designed for exceptional performance, it could transform your listening – even if you never play a single movie blockbuster.