KEF KF92 Subwoofer
KEF KF92 Subwoofer
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KEF KF92 Check Price $599.98 Amazon

KEF KF92-the company was also showing off the new KF92 subwoofer in a corner of its translucent booth.

KEF’s compact (13.9 x 11.8 x 14.2-inch, H x W x D),

gloss-black powerhouse uses dual 9-inch drivers in a force-canceling configuration,

KEF KF92 Subwoofer 500-watt

with each driver powered by a separate 500-watt Class-D amplifier. Sophisticated DSP carried over from the company’s LSX speaker is used for limiting/compression

to prevent distortion at high volume levels, and there’s an Apartment mode that applies a high-pass filter

additional limiting and compression to avoid bass-related neighbor complaints.

Other features include a five-position EQ switch to accommodate various room placements, speaker-

line-level inputs, an LFE bypass, and a pass-through mode.

KEF KF92 Subwoofer

KEF expects to ship the KF92 in November for $2,000.

size, cost, number of drivers and so on

can certainly be manipulated, but ultimately the final result will always be governed by the immutable laws of physics… and you can’t get around them.

subwoofer manufacturers haven’t tried… and KEF has tried harder than most. In order to ensure that one of its smallest-ever subwoofers could deliver deep bass, it even invented an innovative circuit is called ‘Intelligent Bass Extension’ or IBx for short.

KEF KF92 DSP controller

IBx is essentially an algorithm built into a DSP controller that counteracts the natural tendency for a bass driver to roll-off

at low-frequencies but at the same time monitors what that driver is doing to ensure its safe operating parameters are not exceeded.

KEF’s IBx circuit was so successful – and so popular with its customers –

that KEF decided to use it in its larger subwoofers and, most recently, in this new KF92.

KEF KF92 Equipment

KEF KF92 Subwoofer Design

The cabinet of the KEF KF92 is completely sealed, which has a number of advantages over the more common ‘ported’ or ‘bass reflex’ cabinet.

The first and most obvious of these is that whereas bass reflex ports can sometimes create audible noises – usually ‘chuffing’ sounds, but sometimes whistling sounds – you won’t ever get these noises with the KEF KF92 because there is no port.

Another advantage is that because the cabinet is sealed, all the internal metal components are protected from corrosion, which can be a problem in hot, humid environments. 

Yet another advantage is that – all other things being equal – a sealed enclosure has a smoother, more extended low-frequency roll-off and lower distortion than a ported enclosure. (Ported enclosures also have advantages over sealed enclosures, but we’ll deal with those a little later.)

Finally (but far from least, depending on where in the world you live) small furry (or non-furry) ‘critters’ cannot decide the inside of your subwoofer would make a very warm and comfortable home to which they could gain access via the bass reflex port.

KEF appears to be using its own, custom-designed 230mm bass drivers in the KF92: These have hybrid cones made from aluminium-coated paper pulp.

According to KEF, using the paper pulp to form the cone keeps the mass low and ensures an accurate response, while the aluminum skin over the pulp increases the strength of the cone and provides damping.

KEF rates

Although KEF rates the driver with a diameter of 230mm, the design of the driver is such that the Thiele/Small diameter is 175mm, which gives an effective cone area (Sd) of 240cm² per driver, or 480cm² for the system. 

This means that had KEF wanted to move the same amount of air with a single cone, rather than with two, it would have had to have had a Thiele/Small diameter 247mm, which would have translated to a specified diameter of 332mm.

KEF

So why does KEF use two drivers, rather than just one? The most obvious (but wrong!) reason is that since the cabinet is only 330mm wide overall,

a driver that was 332mm in diameter simply wouldn’t fit! KEF uses two drivers for several very important reasons. 

Perhaps the most important of these is that a thousand watts of amplifier power that KEF provides is far too high for a single driver’s voice-coil to dissipate. Spreading this power across two voice-coil assemblies is a far more reasonable engineering proposition

KEF KF92 Crossover

KEF KF92 Subwoofer rear panel
KEF KF92 Subwoofer rear panel

Below the two rotary controls are four slider switches that control (from left to right), Crossover Mode (Internal or External), Equalisation mode (Room, Wall, Corner, Cabinet and Apartment), Phase (0°/180°), and Ground Lift (On/Off).

The correct position of the Crossover Mode switch will depend on where you are sourcing the audio signal you’re using to drive the KF92. If it’s from a component that is supplying an audio signal that has already been through a low-pass filter

(such as the LFE output of an AV receiver, for example) you’d set this control to ‘External’. If you’re sourcing from an ordinary line-level or speaker-level output, you’d set it to ‘Internal’, and then set the low-pass (crossover) rotary control to the appropriate frequency.

KEF KF92 Subwoofer Fascinating

KEF’s equalization mode control is fascinating. I don’t think I’ve seen its like before. Yes, I’ve seen EQ mode controls that offer two or three modes, (usually ‘Off’, ‘Wall’, and ‘Corner’) but I have never seen one that offers five modest.

EQ control

its output is dramatically affected by where it is positioned in your room relative to walls and furniture. KEF’s EQ settings adjust its output to ensure the KF92 will deliver its best performance no matter where in the room you end up putting it… even if you put it inside a cabinet.

EQ mode

As for that ‘Apartment’ EQ mode, the excellent instruction manual supplied with the KF92 contains the following advice about it: ‘Low-frequency sound can travel through walls and be heard in adjacent rooms.

To avoid disturbing neighbors, set the EQ to ‘Apartment Mode’ to reduce the level of very low frequencies (below 40Hz).’

I can see how this would be very useful for apartment dwellers… even though it does kind of defeat the purpose of buying a subwoofer in the first place.

In use

The KEF K92 comes with a small (A5) but comprehensive 22-page User Manual in seven languages,

though almost all the information is intended to be conveyed graphically, via images, rather like Ikea’s DIY furniture assembly instructions.

It’s probably just me, but I found these very difficult to follow, despite the fact that KEF’s manual is a better-than-usual example of the genre.

I then swapped out the stand-mount speakers and swapped in a pair of large, floor-standing speakers to use in conjunction with the KEF KF92

which, of course, meant re-calibrating the volume and crossover frequency controls all over again.

Luckily, the app makes this a quick and easy process, and I was able to skip the subwoofer positioning step entirely.

KEF’s internal

This time, rather than use the KEF’s internal crossover as I had with the floor-standers, I ran the main speakers full-range,

so I was really using the KF92 to reinforce to the main speakers’ own output, plus extend the bass downwards even further. In this role, the little KEF KF92 again excelled.

I found it impossible to hear the point at which it took over the deepest bass, so it was essentially a seamless integration.

The only real difference was that whereas with the stand-mounters the KF92 kept up as I turned the volume up,

I thought it struggled just a little bit at very loud volume levels when used with the large floor-standers.

verdict

The only issue with wrapping up this review is that I’ve already wrapped up because, as I wrote earlier, the bass from the KEF K92 is awesome! 

This is a subwoofer from a company that has been building subwoofers for a long time, and hi-fi loudspeakers for a whole lot longer,

so it knows what it’s doing, but with the KEF K92 the company has excelled itself

I know this is a big call in a crowded market,

but I’d say KEF’s K92 may be the best small subwoofer of them all.

FOR

  • Deep bass extension
  • Low distortion
  • Compact dimensions

AGAINST

  • switch is limited
  • Proprietary speaker terminals

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