KEF 'UNIVERSAL WIRELESS' SYSTEM Innovative units deliver fine sound — without the wires Designed with surround in mind, this system has wider applications, says Andrew Everard

One of the major drawbacks of surround sound systems is the need to run cables from the main amplification to the rear channels.

Yes, you can lay them under the carpet, but most people tend to use longer runs round the room — and then realise there's a doorway or a window in exactly the wrong place.

It's hardly elegant, so it's no wonder that a lot of design effort has gone into finding ways around the problem, such as the many 2.1channel systems on the market using digital signal processing to create the illusion of extra channels, or bouncing sound around the room from side-facing drive units.

There is an alternative in the form of wireless transmission, seen in a range of packaged homecinema-in-a-box systems and in some set-ups from specialist speaker manufacturers. Usually radio is the chosen method of transmission, but some systems have tried infrared light, adopting a variety of strategies to ensure the "line of sight” signal isn't broken.

But whichever method is chosen, the idea is the same: a transmitter at the "system" end takes the audio signals and sends them to one or more remote receivers, which also contain amplification. All that's needed is a power supply near to the rear speakers — we can't quite send power wirelessly yet!

KEF is the latest company to launch a wireless speaker system, and with the benefit of having seen how well others have tackled the problem, the Kent-based manufacturer has developed a package that's as neat as it is sophisticated. It comprises a transmitter with both speaker-level and line-level inputs, plus a pair of transmitters pre-programmed to take the left and right channel signals, each of which contains a .50W digital amplifier. And while there's a version dedicated to the company's KHT (KEE Home Theatre) speaker range, and designed to bolt onto the bottom of the KHT5005 speakers, there's also a £400 "universal" model, considered in this review, designed for "free-standing" use with other speakers.

There's some clever technology here: the system uses the 2.4GHz radio band but — to avoid interference from home wireless networks, and indeed mobile phones, microwave ovens and the like — KEF has designed "channelhopping" software. This detects problems and shifts the transmissions away from other signals you may have floating around your home in an increasingly wireless world. What's more, the system keeps monitoring and "hopping" if required — the full name is Advanced Adaptive Frequency Hopping Spread Spectrum.

PERFORMANCE

High-Fidelity Adaptive Differential Pulse Code Modulation is used for audio transmission, claiming CD-quality sound and a range of up to 25 metres, and this is what got me thinking about other uses beyond the intended de-cabling of surround speakers in multichannel set-ups.

Two connection cables are provided — one terminated with four speaker conductors and a keyhole-shaped plug to attach to the transmitter unit, the other with two phono plugs at one end and a 3.5mm stereo "headphone" plug at the transmitter end, so it was easy to experiment with connection to everything from amplifiers and small systems to CD players with variable level output, and even my laptop.

The transmitter and receivers come with mains adaptors — a small plugtop one for the transmitter, heftier in-line units for the receivers with their built-in amps — and once all is connected up and the power switched on, blue flashing lights turn steady to show communication is established.

It's the performance of the package that makes all this possible: it is entirely transparent in operation, and has more than enough power to deliver "main channel" stereo music — at least in average-sized rooms and with speakers of average sensitivity or higher — let alone fulfilling its surround duties. I played everything from solo instrumental music, allowing the system to show how well it handled the weight of piano or the sweetness and bite of violin, to larger-scale orchestral and choral music, and in every case the KEF proved more than up to the job.

So, this is a product with obvious massappeal, offering convenience without a sniff of compromise. I think it will do very well indeed. (