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April 2004 | IEEE Spectrum | NA 51

RESOURCESThe Solution

Was SakeStrange ingredients make

a better loudspeaker BY TEKLA S. PERRY

EUREKA: How can wood be made pliable enough

to form into loudspeaker cones? That question

stumped engineers for decades until Satoshi

Imamura discovered the answer: rice wine.

Some engineering problems takelonger to solve than others. Inventorsstruggled for decades to find the rightfilament material, before ThomasEdison tried carbon and made a prac-tical light bulb.

Toshikatsu Kuwahata, an engineerat the audio factory of JVC (VictorCompany of Japan Ltd.), in Yokohama,is no stranger to such lengthy strug-

gles. He wrestled for more than 20 years withhis own personal challenge—making aspeaker cone that could be manufactured inquantity out of wood.

The cone is the part of the speaker thatvibrates to produce sound. It is typicallymade out of paper pulp, polypropylene,polyester, or some similar pliable material.But wood, Kuwahata knew, has qualitiesthat could make it a superior choice forsound reproduction. For one thing, soundpropagates very quickly through wood,which means that the speaker can producea wide range of frequencies. Wood also hasan internal damping effect, which leads to

a smoother frequency response. This is oneof the main reasons that wood remains apopular material for musical instruments.

But unlike the parts of an instrument,the material used for a speaker cone mustbe severely deformed to form the requiredshape. And when Kuwahata tried to formthe cone out of wood, even thin sheets ofwood, it cracked.

He thought he had the solution once, twodecades ago, when he took a pile of paper-thin sheets of wood and successfully gluedthem together into a cone. Unfortunately,developing an economical manufacturingprocess proved impossible.

Then, five years ago, a colleague, SatoshiImamura, was dining at one of his favoriterestaurants. Imamura contemplated thetexture and malleability of the dried squidhe was chewing. He asked the waiter how ithad been prepared, and the waiter explainedthat the squid had been soaked in sake.

Imamura and Kuwahata tried soakingthe speaker wood in sake. It worked! (Theyalso tried Suntory whiskey; it didn’t.Imamura isn’t sure why, but he theorizesthat there is something unique about theacids in sake, which is simply fermented,as opposed to those in whiskey, which isdistilled after fermentation.)

The sake makes the wood sheets mal-leable but—crucially—withoutaffecting their strength. Thesheets are then infused withresin and a mold-release agent.The resin prevents the woodfrom absorbing moisture, help-ing it to retain its shape in hightemperature and humidity longafter it’s been molded into theshape of a speaker cone.

This year, JVC introduced itsfirst wood-cone speaker prod-uct based on Imamura’s process,the EX-A1, an executive desk-top-entertainment system with30-watt wood-cone speakers.JVC expects to use the wood-cone speaker technology inlarger audio systems in the fu-ture. The cones in this luxuri-ous model are made of birch,and the cabinets are solid cherry.They are packaged with a com-bination amplifier, tuner, andmultiformat DVD/CD player,with both audio and video outputs. Most important, thesound is seductive, even in anoisy environment.

The system ships in May, at a suggested retail price of US $550. Back in Maebashi,Japan, his mission accom-plished, Kuwahata has an-nounced his retirement. � TO

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52 IEEE Spectrum | April 2004 | NA

It’s a classic image, theflickering light of the TVproviding the only light in adark room, the faces in theroom changing color as theTV screen changes.

But lighting as a by-product of television hasalways been unintentional.Until now, anyway.

Philips Electronics NVthis month began shipping

flat-screen televisions thatare also room lights.Philips’s Ambilight technol-ogy projects backgroundlight from the rear of thetelevision onto the wall,creating a halo around thetelevision, which softlylights the room. The viewercan adjust the color choiceand brightness via remotecontrol (whether the televi-sion itself is on or off). Orthe system can be set to anautomatic mode, in whichthe lighting is continuouslyadjusted in relation to theimage on the screen and tothe overall brightness ofthe room, determined bybuilt-in sensors.

The Ambilight feature isavailable in the PhilipsMatchline 32-, 37-, and42-inch LCD FlatTVs (pricedat US $6000, $8000,and $10 000) and in thecompany’s 50-inch plasmaFlatTV ($10 000). —T.S.L.

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YOU NEVER KNEW YOU NEEDED ITTVs that light up the room—even when they’re off

AUDIOPHILES: Toshikatsu Kuwahata [right] and Satoshi

Imamura developed these wood-cone speakers at JVC

in Yokohama, Japan. Larger speakers are planned.