The British firm KEF is well-known for its high-quality loudspeakers. Both its professional monitor speakers and its audiophile-grade home loudspeakers are generally given good reviews. The primary downside is usually the price. The KC62 is no exception - its price is quoted as $1500 each - but for some users, it is worth the price. (See below.) This speaker is about the size of a basketball, but it weighs 31 pounds. Its performance is made possible by the combination of three primary features - its opposed dual-driver design that shares a single magnet structure, a patented cone surround support material, and the special dual-channel Class D amplifier with integrated DSP.
The patented P-Flex speaker cone surround can effectively resist the sound pressure generated by the sound while breaking the traditional suspension edge design’s sensitivity limitation. The design is inspired by Japanese origami art. It adopts a unique folding design to resist internal air pressure.
Another element behind creating a better performance for KC62 is the well-known KEF Music Integrity Engine. It is a series of DSP (digital sound processor) calculations designed for KEF products, including iBX (intelligent bass extension technology, a current-sensing feedback loop from the actual voice-coils that feeds information about incipient distortion to the DSP.) and continuous SmartLimiter that analyzes music and prevents sound breaks. Its dual drive unit is driven by a specially designed 1,000W RMS (2 X 500W) Class D amplifier, which provides excellent control and generates instant explosive power when needed.
Some of the technology incorporated into the design of the KC62 had been used previously in the larger KEF KF92 subwoofer, but the topology of the drivers in the KC62 is unique. KEF invented a topology in which the two driver units are mounted on the same support assembly. Both units share the same magnet system, but the two voice coils are of different diameters, so one can move inside the other at large excursions, and the middle is isolated.
This design can reduce the volume of the entire speaker by one-third. Since the two units are assembled back to back, their vibrations will cancel each other, and the output gain can be increased by 6dB. There is no compromise in the performance of the two units at the same time. One important thing noted by most reviewers is that this sub contributes no noise itself - no vibration or port noise - just very deep bass. KEF specs its frequency range as 11Hz to 200Hz (-3dB) While it may not be able to fill a large room with high-level bass, in situations where it is most likely to be used, that response is amazing.
A surprisingly elaborate control and input/output panel on a side panel has the usual (but unusually nicely detented) rotary volume and crossover knobs, 0/180 degrees phase and LFE/Normal toggles, plus a five-position EQ switch that is used to tailor the sub's response according to its placement in the room. There are both line- and speaker-level inputs, and a 4-position high-pass filter can be applied to the line output.
Several reviews of this little sub have been published, and my information comes from some of these. Perhaps the most helpful is one by Gordon Lyn at HiFi Reports. Another excellent review is by Mark Craven at Home Cinema Choice. You may also want to see reviews at WhatHiFi.com, SoundAndVision.com,
Stereophile has a review. but it is short on technical details and focuses too much on the speakers that might be used with this sub. Chris Heihnonen at ReferenceHomeTheater.com made these comments: "it provides more bass from a box this small than I thought was possible thanks to its unique design. .....Value isn't great since a pair of dual 12" sealed subs is the same price though much larger in size." I might add that if you don't have room for a much larger sub, this one could be worth its steep price. It can add that lower two octaves of bass when used with small monitor speakers in a control room, for example. James Michael Hughes at StereoNet.com has an excellent review and remarks on the amazing low-frequency response of this little sub. He says this: "I would never have believed a sub so small could reproduce frequencies so low. There is no doubt in my mind that KEF’s new KC62 is a breakthrough product, one that redefines what is expected from a small subwoofer. It’s not inexpensive, but when you consider what it does and how it compares to bigger more expensive designs, it actually offers very good value."