The Exciter: a subwoofer in the windshield


By Lawrence Papoff

Cars are getting smaller. Subwoofers will have to follow suit as the space for housing them in the car shrinks. But what about sound reproduction?

Generations of car-owning audiophiles have lavished time and money making sure their vehicles’ stereo systems produced concert-hall quality sound. Will they still want to if what they hear is cramped and tinny?

Car parts manufacturer Magna International wanted to make sure that shrinking cars didn’t bring with them low-quality acoustics and shrinking audio accessory revenue. So it bought the rights to the Exciter, a device that uses a car windshield to reproduce sound on par with the traditional subwoofer — at least Magna hopes it will.

To find out, Magna turned in May 2008 to auto research group Auto21 to see if the device could go from the drawing board to the windshield.

Based in Windsor, Ont., Auto21 farms out research work to a network of researchers in universities across Canada.

The project, dubbed Acoustovision, went to auto noise specialist Dr. Colin Novak of the University of Windsor’s automotive engineering department.

“Think of it as two mechanical springs — 12 inches long and one inch by one inch mounted at the base of the windshield glass,” said Novak describing the device.

Nicknamed exciters, each spring holds a piezzo sensor about the size of a dime. The piezzos receive signals from the rest of the sound system.

“It’s their movement,” he says, which causes the exciter to move up and down, and thus excite the glass, turning the windshield into a speaker. Instead of a conventional paper speaker, the glass moves instead, which in turn moves or pushes the air to create the sound waves we hear.”

He assures that the movement is imperceptible and will not compromise the crash resistance of the windshield. That’s been tested as has weather and vibration resistance.  

What about the sound quality? Novak is proud to say that the quality has surpassed the sounds broadcast by the standard subwoofer.

All that remains is whether the device will be able to withstand the rigors of the manufacturing process. That will take about 18 months, he says.   

There’s a bonus.

“Depending on the model, the exciter can reduce a vehicle’s weight by up to 20 pounds, increasing the vehicle’s fuel efficiency,” Novak says.