Subwoofers

KEF's new subwoofer is calling out for a slick nickname. From the brand that brought us the Blade and Muon speakers, plus The Reference range, comes the ...KC62. This moniker makes it sound like something that's fallen off a spreadsheet rather than what it is, which is arguably the coolest subwoofer I've ever had a chance to play around with. Maybe it will grow its own nickname over time, like KEF's 'Eggs'. It's certainly a cracker.

The KC62 was announced earlier this year with much fanfare by KEF, which clearly believed it was on to a winner. Here, went the blurb, was a subwoofer for everyone (well, those with a spare £1,400). Cute and compact, and packing patent-pending technologies around its dual driver implementation, the KC62, we're told, means that 'deep and powerful bass is no longer solely the domain of big-shouldered, massive subwoofers.'

Now, some of my best friends are massive subwoofers, but a compact sub has considerable appeal, mostly because it's easier to accommodate in your room, and far more likely to be allowed into a typical lounge. And, adds KEF, smaller models can be more practical for systems using multiple subs. There's also the fact that smaller environments don't actually need a woofer capable of hitting Armageddon SPL levels at 10m.

Iron Law Man
The white paper for the KC62 goes into detail about Hofmann's Iron Law. The concept of audio engineer Josef Anton Hofmann, this 'law' outlines three parameters of loudspeaker design – cabinet volume, low-frequency extension and efficiency – and says that one of these must be sacrificed in pursuit of optimum results in the other two. Related to subs, this means that a big box is needed to achieve a high output and deep bass. KEF thinks differently.

In the KC62, two 6.5in woofers are mounted in a force-cancelling (opposed) configuration. This isn't particularly unusual – the same method is used in KEF's considerably larger KF92 sub – but what's going on behind the scenes is.

In place of the standard twin magnet system, the KC62 uses just one, while the voice coils and suspensions of the two identical drivers themselves are not identical. One of the coils has a larger diameter, allowing the two to overlap and 'travel within their own gap without colliding.' KEF has named this patent-pending technology UniCore – which proves it can still think of cool names when it wants to – and claims the result is a greater excursion and higher potential SPLs. Additional tweaks around suspension mass and magnetic flux are then deployed to ensure the KC62 doesn't have two drivers behaving differently.

Heavy Metal Thunder
This is all the theory. In practice, what you get is a subwoofer that's about the size of football, but with the weight of a small elephant – well, 14kg. Some of this surprising heft will come from the KC62's aluminium cabinet, which not only enables a sultry curved design, but works to manage heat dispersion from its 2 x 500W Class D amp stage. If you think that 1,000W seems like quite a lot to drive a pair of 6.5in woofers, you'd be right.

The styling of the KC62 is clearly informed by the brand's LS50 bookshelf speakers and, to a lesser extent, its Q Series models. It replaces the square subwoofer aesthetic of old with rounded sides and corners. A flat bottom stops it rolling around your carpet.

Measurements are approximately 25cm wide in all directions, but the curves make it seem even smaller than this. There are no grilles for its woofer duo, so beware of pets and toddlers.

Terminals and controls are mounted on a tidy rear panel, and include crossover, volume, phase, LFE and stereo line in/out. To save space, speaker-level inputs are via a Phoenix connector. There's also a power switch (obviously) – when on, the status light on the KC62 glows orange to indicate the sub is in standby. When it wakes, this light glows white for six seconds, and then fades off. The reason I've mentioned this is because I experienced occasions where the sub refused to wake from its standby mode (presumably because the output level from my AVR was too low), and there appears to be no way to manually turn it 'on'. Raise the volume a bit and wait.