Mondo Audio (Feb. 1997)--THE NXT BIG THING

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Rare are the occasions when a British hi-fi company makes the financial pages of the major newspapers. Rarer still are the times when British companies force the hands of American companies. But the Verity Group has done both, achieving what must be the audio equivalent of turning lead into gold: The development of a wall-mountable, flat-panel loudspeaker that works. Unlike electrostatics or other classic dipoles, it doesn't need space behind it, making it an interior decorator's dream speaker.

Verity Group, which has been mentioned in this column before, is the parent company of venerable British makers Quad, Wharfedale, Mission, and Roksan. Once it found itself the owner of a quartet of complementary brands, covering a wide range of budgets and tastes, the company realized that it could justify centralizing its design headquarters, just down the road from the main Mission factory. And one of the first projects to emanate from V-Labs, as the R&D center is known, is a design that transcends individual brand application: NXT, the technology that made Verity shares jump overnight.

From 15 pence (25¢) on the morning of the announcement to 23 pence (38¢) by the end of that day, the price went up as high as 44 pence (74¢) in the aftermath of the announcement. The competition immediately started muttering the words "smoke" and "mirrors," while industry veterans recalled myriad launches at Consumer Electronics Shows of flat speakers disguised as paintings, which uniformly sucked.

Only this time, it's for real.

Wharfedale's managing director, Stan Curtis, while studying materials and technologies suitable for noise isolation in aircraft cockpits, saw an item in an electronics magazine concerning a distributed-mode loud speaker (DML), an idea pioneered by the British Ministry of Defence Defence Research Agency in 1994.

Curtis and Henry Azima immediately recognized DML's potential, and Verity Group became the sole licensee. It took two years of research and development for the concept to evolve from the theoretical to the practical. Azima told me that, as of late November 1996, Verity had applied for 23 patents, with at least an other 10 to follow.

Distributed-mode describes the principle under which the NXT loudspeaker operates. Unlike nearly all other viable speaker types, which work as pistons moving air (let's leave gases out of this discussion, okay?), DML uses and controls a flat panel's bending modes. A detailed explanation of how this all works is much more than I have room for here, but the upshot is a panel that can be manufactured from any number of materials, in thicknesses from about 3 to 20 millimeters and in sizes ranging from 25 square centimeters to 100 square meters. The panel can be driven from a single point by a moving-coil motor, as in conventional speakers, or by a piezo electric motor. The trick lies in con trolling the panel's resonant behavior. And it is the latter that required the most research.

The first thing the design team had to do was abandon its preconceptions, including the notions of using pistonic motion and electrostatic or electromagnetic principles.

Indeed, DML meant embracing the antithesis of conventional, cabinet-mounted speaker design, in which any movement of the stiff en closure panels is unwanted; DML does not even use an en closure. The transducer creates bending waves in the panel, its behavior dependent on a list of characteristics out lined in the company's white paper:

surface density, bending stiffness, the panel's geometry and surface area, the location of the drive point, the drive-unit type, the shear modulus of the core, internal damping, the method of mounting the panel, and other "interrelated factors." To quote the paper, "The correct blend of these parameters will specify a panel construction that will result in good distributed mode behavior.

Should one get this wrong, the panel will of course radiate acoustic energy, but it will not be a loud speaker anymore." Additionally, the NXT speaker is bipolar in operation (above a given frequency), radiating sound across its entire surface. Surprising benefits include diffuse sound radiation, with uniform directivity across the frequency band (thereby eliminating problems with off-axis seating, which normally suffers from irregularities in tonal balance), and, curiously, sound pressure levels that decrease linearly relative to the speaker lo-cation so that the sound appears to fill a room at a constant level. This is in contrast to conventional speakers, which adhere to an inverse-square law for power loss with increasing distance. Another bonus is that, should you eschew the divine option of wall-mounting an NXT speaker, its behavior in free space (given the front-plus-rear radiation) will provide an extra 3 dB of level, which is akin to doubling the power of your amp for free. Although this advantage is sacrificed when the speaker is wall-mounted, its performance is other wise unhindered. Free-space operation, how ever, isn't the main point; making the panels disappear is. So you can probably see what's coming.

Given that an NXT speaker can be made from all sorts of materials, finished in a variety of ways, and be used with or without an enclosure, the possibilities are virtually endless. And Verity, being a sensible company, isn't going to let the audiophile com munity pee on its parade. In the best entrepreneurial spirit, the company is courting licensees from all fields. The first licensees, though, are three of its own: Mission, Quad, and Wharfedale. To manage this, the company created a new division, New Transducers Limited, with Henry Azima in the driver's seat. The hope is that it won't be long before companies outside the hi-fi industry check out NXT's potential applications, to wit:

Computers Think about what a hassle it is extracting stereo sound of reasonable quality from your notebook computer.

Now picture fold-out "wings" or even an entire notebook computer's lid made from an NXT speaker. And while you, I, and other computer users with audiophilic tendencies might go all the way and use "real" hi-fi systems for the audio portion of our computing, not everyone wants full-blown speakers or even Bose RoomMate/JBL Control 1/Rock Solid-sized mini-speakers flanking his monitor. Again, a fold-out "wing" could do the trick.

Home Cinema: Yep, an entire projection TV screen could be made from an NXT speaker simply by finishing it with an appropriately reflective coating. Bye-bye hard to-hide center-channel speakers. And if you're one of those lucky souls who has the space for a 100-inch or larger screen in his viewing room, it could contain the front left and right speakers, too. Verity has already trademarked its center-channel/screen model as Sound Vu. As for the left/right and surround speakers, well, NXT's dispersion is diffuse, making it ideal for cinema-style listening. No hot spot in the room-another dream come true.

Car Stereo: Why not make a car's entire parcel shelf or even its door panels from NXT? Parts of the dashboard? The headliner? The glove compartment's door? Hell, if you're the owner of a big MPV or a Winnebago, you could pack in enough speaker to drown the blast of any low-rider at full bore.

Custom-Installed Multiroom Systems:

Sick of cutting holes in the wall to camouflage the speakers in the bathroom, kitchen, or dining room? NXT is an installer's dream. It's made to become part of the wall;

you won't even know it's there. Verity has already designed ceiling tiles from NXT speakers, under the trademarked name of SonTile.

Professional Applications Verity has identified such uses for NXT as audio notice boards in museums and at exhibitions, public address systems, airplane cabin PA systems (where space is always at a premium), you name it.

The list could go on forever. You know those silly greeting cards with synthesizer chips on 'em? NXT 'em. How about an NXT mini-speaker built into the lid of a portable CD player? Or boom boxes on diets, ultra-flat telephone handsets, higher-fidelity cellular phones, wild headphones, and "talking" briefcases? What hasn't yet been brought up, though, are high-end products.

Azima dismisses mutterings about NXT's diffuse dispersion being ideal for home theater but lousy for hi-fi. Like any new technology, it needs refinement. Affordable, commercial NXT products aren't expected to be in stores before 1998, so it's still early. Azima pointed out that the practical operating range for an NXT panel is 100 Hz to 20 kHz, and you could get deeper bass by adding an enclosure or making hybrids with cone-type woofers. Because sub-

woofers came of age long ago, few would object to a couple of NXT panels being augmented by a subwoofer sitting in the same place that today's subwoofer resides.

With NXT, it looks like Verity has a winner on its hands. It created enough of a buzz to cause an American company that has a U.K. office to issue an announcement regarding its own "flat-panel speaker technology." Noise Cancellation Technologies-with offices in Stamford ( Connecticut), in Cambridge ( England), and in Tokyo-revealed that it had been working on a not totally dissimilar piezo-driven flat panel speaker for two years. The press re lease was accompanied by a list of colleagues, including automotive heavy hitters like Magneti Marelli (which makes the electrics for Ferrari) and the U.S.A.'s largest manufacturer of car headliners. And, sure enough, NCT's working prototype fills the ceiling of a Ford Mondeo, demonstrating what has been fetchingly named TDSS: Top Down Surround Sound. So it looks as if one hell of a battle is brewing.

Verity launched NXT to the U.K. press in September, in Tokyo in October, and in Germany in December. The American launch is planned for Las Vegas, at private showings during the Consumer Electronics Show this January. The company has never been more bullish. So maybe now it's safe for you to tell your nagging decorator/architect/spouse that the future is gonna be flat.

(adapted from Audio magazine, Feb. 1997)

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