KEF introduces the KF92 subwoofer to complement the R series. The model is based on two oppositely directed 9 ”aluminum and paper drivers. According to the manufacturer, the modest dimensions did not affect the power of the subwoofer: two D-class amplifiers of 500 W are hidden in the case, and the sound pressure reaches 110 dB. Such indicators, according to the idea of the company, should provide punchy bass at any volume.
To maximize performance, KEF engineers equipped the KF92 with iBX and Music Integrity Engine technology. The press release says that the first algorithm “unlocks the speaker’s potential and enhances the depth of the bass,” while the second adjusts the sound based on the location of the subwoofer.
Model KEF KF92 reproduces frequencies from 11 Hz. Based on the information from KEF, the sub can operate in such a low spectrum thanks to the special arrangement of the speakers, large coils and powerful enlarged magnets. The rear panel of the KEF KF92 has a very rich settings panel and connectors. There is also a massive radiator at the back for heat dissipation, which is designed to always keep the insides of the sub in “optimal condition”.
The speed and musicality of the KEF KF92 subwoofer will perfectly complement the sound of a system with high-quality speakers, and its modern appearance and compact dimensions will fit perfectly into a fashionable interior … the benefit of the model of a manufacturer specializing in the production of subs. KEF has produced a subwoofer that really deserves to be noticed.
KEF KF92: Features
The 1000W RMS Class D amplifier KF92 (500W RMS per driver) delivers tremendous power while delivering incredible levels of control. This improves timing accuracy and dynamic response, creating a more detailed sound, closer to that of a studio.
Two 9-inch KEF converters have been specially designed for the KF92. They are equipped with a hybrid aluminum-paper cone, an enlarged motor system and a voice coil. They offer incredibly low distortion and fidelity, so every bass moment is revealed even when it is operating at extreme levels.
In this model, KEF decided to show its ability to “squeeze” monstrous sonic power into a very compact cube. However, the possibilities that the new subwoofer concept opened up came as a big surprise even for us. Today, finding an active sub for a home system is not a problem. In the segment up to 50 thousand dollars, there are a lot of simple, but rather lively “lightweights”. Up to 100 thousand the offer is even wider: there are also neat fast “eight-inch” models in a closed design for musical triphonics and heavy passive-radiator or bass-reflex guns of large caliber. In the category from 100 thousand, there are already universal copies with advanced settings, from 200 – especially powerful options for large halls, from 400 – systems with an audio processor, room correction, etc.
But when you see KEF KF92 live for the first time, you don’t immediately understand what place it occupies in this market hierarchy. Against the general background, it seems rather miniature – many popular subs are much more impressive. At the same time, the model has a stylish design with expensive finishes, a heaped up rear panel and suspiciously serious heat sinks that contradict the declared economical class D amplification. Moreover, the device cannot be unequivocally attributed either to theatrical “thugs” or to musical “singers” due to the unusual acoustic registration. In it, two active heads work in push-pull mode for a common closed volume.
And the fact that the KEF baby will have to be paid for as a giant from the “over 200” category finally breaks the pattern. But let’s not jump to conclusions. KEF also has a Reference 8b – a sub, which outwardly also does not resemble a monster in any way, but meanwhile it is several times more expensive than the monitored novelty! Why? The explanation lies in a unique engineering concept that has invested a lot of scientific potential and experimental work.
The fact is that there is no clear direction in modern subwoofer construction. Someone prefers long-stroke piston drivers, someone – huge diffusers with a small offset. Some consider it extremely important that the bass head is sensitive and responsive, while others at this time build excellent bass machines on tight and heavy drives. There is no consensus either about the best acoustic design, or about the need for room correction for the bass signal, or even about the optimal place for installing the sub in the room.
KEF was looking for a solution that combined the advantages of all of these options. Therefore, they preferred drivers of not too large caliber with a light diffuser, but at the same time endowed them with a powerful voice coil – for a colossal input power. The required radiation area was obtained by an elementary doubling of the number of heads, placing them back to back. In this case, all directed inertial and reactive forces during the operation of the heads are mutually compensated. The circuit is not new, it effectively reduces the vibration of the case and is used by some other manufacturers. KEF called this design the Efortless Dynamic.
But the main thing is a pair of amplifiers of 500 W (RMS) each. In the Reference 8b mentioned above, they receive a signal from a special DSP, and such a drive has everything – the power reserve, forcing the drivers to react instantly and reach high amplitudes despite the huge back pressure inside the sealed housing, full control of the diffuser travel due to load distribution and optimal damping, and also the ability to flexibly optimize the characteristics of the path through signal preprocessing.
So, KEF KF92 offers all the same, only at a lower price and in a more compact body. 22.5cm heads – Specially designed drivers with composite paper and aluminum cones. The concave shape ensures an even distribution of mechanical forces from the voice coil and extremely high dynamic stiffness. The power of the amplifying link is exactly one kilowatt, therefore, even for class D, a solid heat sink was needed. And the role of DSP here is played by the newest Music Integrity Engine – a phase-frequency correction module with five settings. And it is due to him that the baby KEF KF92, which itself weighs only 20 kilograms, shows in its characteristics some fantastic linearity parameters starting from 11 Hz.
In addition to the operating mode selector, the KEF KF92 has a phase switch and a bandwidth control (up to 140 Hz), high-level inputs (implemented through a special block) and low-level outputs (full band or with filtered bass). The interface for connecting the KEF KW1 adapter allows you to send a signal wirelessly with a minimum delay.
We tested the British novelty in a cinema system with acoustics installed in the walls. In such projects, the effect of a real cinema is easily achieved, but it can be problematic to adjust the low frequency channel due to the fact that the subwoofer is moved either into the corner of the room, or behind the sofa, or generally into a special niche. These are the conditions we modeled for the KEF KF92 as well – we put it near one of the corners just behind the seats.
First, let’s try the basic settings: turn on the mode toggle switch to LFE, set the full bandwidth and zero phase. In this case, all the necessary settings for the LF channel (delay, level, cutoff frequency and slope) were set by an external processor for the actual placement and parameters of the built-in speakers (in our system, their range started from 60 Hz).
We turn it on and are surprised – its register KEF KF92 reproduces without any compression, laxity or hum. It really “chops” like a big powerful sub, without distorting or tightening even the lowest fundamental sounds. In principle, you can stop at this option – the result will appeal to any movie lover. It is suitable for both blockbusters and melodramas – in action scenes it amazes with effects, and in calm scenes it pleases with naturalness. Except that in musicals it does not always turn out beautifully – the entire orchestration, ideally, should be localized, as it were, on the screen, but the sub slightly pulls the bass instruments towards itself.
Let’s try to fix the situation. We put the switch in the Manual position, we limit the working band of the bass machine with the same system 60 Hz (but at the same time we expand the LFE channel so that the filter in the processor does not affect the result). It remains only to select the optimal alignment characteristic. In the default Room, we get a sound that is very similar to the base one – there are almost no changes in dynamics, showiness and solidity. But the consistency did not get better – only some of the tools were localized along the front, and some literally moved to the sub. Switch to Wall and get a noticeable clearing of the rhythmic structure. Gone are the viscous shades in the low register. Cool! But the bass is still often localized not in front, but where the bass machine is.
Corner is the mode that perfectly decoupled low-frequency sounds and effects from the subwoofer in our test system. This regime is also interesting in that tectonic components are distinguished in it, and fast shock components are slightly weakened. We get an excellent sound for night viewing – large-scale, voluminous and even threatening, but at the same time comfortable for perception and does not make you flinch from too noisy explosions. Only for music, this setting is not very suitable.
The Cabinet mode seemed to be the most indistinct, in which the bass stood out noticeably in the region of 30 – 40 Hz. But again, you need to make a reservation – specifically in our case. If the sub is removed from the walls and corners, then this alignment will probably be the best for working with monitors in scheme 2.1. The Apartment mode gives even more bass boost, and the characteristic here seems to rise at the edges of the flange, since the bass is very dense, and the effects are extremely seismic. Such a correction is suitable for large rooms and especially for those cases when the subwoofer will be installed according to science – so as to excite standing waves in the room at a minimum.
And briefly about the most revealing qualities. The KEF KF92 performed well with the widest possible bandwidth. It is really fast and clear with an extended range, and does its job very cleanly, without the slightest overtones. It also easily matches the satellites – we fed a range from 40 Hz to the front channels, and the subwoofer was limited to 100 Hz and we got an amazing result – the bass didn’t just move forward, but literally went off the screen and was embodied as a physical object. However, for this we had to again turn to the help of the processor – in particular, to establish by ear the optimal value of the time delay.
For me personally, this sub was the first in twenty-five years of expert practice, which showed musical abilities in a purely theatrical system. There is not the slightest doubt that the KEF KF92 will turn out to be just as good in musical 2.1. Of course, in a classic configuration without a processor it will be more difficult to achieve bass coherence, but I do not foresee any problems – just try to find the optimal place for the KEF KF92 and experiment with matching. This is a good option if you have nowhere to put large floorstanding speakers.