Immersive sound is the siren song of car audio makers, luring customers not to their deaths but to the options list. Audi offers Bang & Olufsen’s 3D Premium Sound System, Mercedes rocks Burmester’s high-end 3D surround-sound system, Range Rover’s Meridien promises 3D in-car surround sound. Bose has been pitching surround sound since 1996, after making its first factory-installed audio system for the 1983 Cadillac Seville.
Recreating the preternatural, submersing acoustics of a medieval cathedral these days requires a bouquet of speakers and a lot of power. The Bowers & Wilkins system in the Maserati Levante can put out 1280 watts through 17 speakers. The NAIM unit in a Bentley Flying Spur dishes out 2200 watts through 21 speakers. The Revel Ultima 3D system puts 28 speakers and 1200 watts inside the Lincoln Aviator. The 2021 Cadillac Escalade’s Platinum trim comes with a 36-speaker AKG Studio Reference system.
Manufacturers could keep adding speakers until there’s no room left in the vehicle, or maybe the next step is the approach Continental Automotive is taking. With its Ac2ated technology, the German supplier best known for tires turns the vehicle into a speaker, a process that could save weight, energy, space, and change the way designers approach the vehicle’s cockpit.
Ac2ated uses what are called actuators (hence the name) or exciters. An actuator is a small, puck-like cylinder that has an active surface capable of high-frequency vibrations. “We are putting an exciter on a surface in a vehicle,” Continental’s innovation and Human Machine Interface expert, Susan Drescher, said, “and giving it a very slight vibration to create a sound from that surface so that your car’s pieces become the speaker, as opposed to having speakers installed in the car.”
The principle is the same one employed by violins or acoustic guitars, where strings send vibrations resonating through the instrument. The science works on glass and plastic, too. The result, according to Continental, makes vehicle occupants “feel as if they are sitting in a concert hall surrounded by sound.”
The technology isn’t rare. Amazon sells Dayton Audio exciters for $20, and companies like Solid Drive make systems for home and office use. The tech isn’t new, either. Freedom Drivers hit the market in 2007, and in 2013 United States auto industry supplier Johnson Controls produced an excellent behind-the-scenes video of its Lightweight Overhead Audio System with help from studio engineer Tony Bongiovi (Jon Bon Jovi’s second cousin).
Continental first showed Ac2ated at the Consumer Electronics Show in 2018. At CES 2020, Continental announced a partnership with Sennheiser that paired Ac2ated with Sennheiser’s AMBEO 3D technology. AMBEO provides algorithms that enhance the digital source signals, spreading sound throughout the vehicle with improved spatial reproduction and fidelity.
Because the actuators live in the vehicle’s structure like traditional speakers, implementing Ac2ated properly requires working with an automaker as the vehicle is being designed, a relationship like the collaboration between Rolls-Royce and its Bespoke Audio producer for the Phantom II.
Continental says that A-pillars are generally a good place for exciters to produce high frequencies, the door panels are suitable for midrange, and the headliner and rear shelf work best for bass. However, an actuator can be placed almost anywhere, with stiffer materials working better than softer materials. “We work very early on [asking an OEM],” Drescher said, “what are you covering the surfaces in, how much air space is in that surface because you need some air space, so you’re not going to pack padding around it.”
After the actuators are placed, Continental and Sennheiser fine tune the system. Ac2ated’s dynamic range covers the spectrum of human hearing, from 20 Hz to 20 kHz and beyond. The system can be programmed with the same noise-cancellation features as today’s systems. And audiophiles retain control of bass, treble, balance, and fader—everything they’re used to controlling.
Ac2ated’s primary benefit isn’t in replacing traditional sound reproduction, however. The most important advantages are saving weight and space, freeing up design, and conserving energy.
According to Continental, a conventional high-end audio system uses between 10 and 20 speakers—even the Dodge Charger can be optioned with 19 speakers—and weighs up to 33 pounds, taking up a total volume from 0.4 to 1 cubic foot. Drescher said Ac2ated’s tweeters and midrange units aren’t much smaller than traditional speakers, but the bass unit is substantially smaller, and the subwoofer doesn’t require an enclosure “because your car is the box.” The Ac2ated system requires fewer pieces, she said, “maybe 13 as opposed to … 20 speakers” producing 12-channel audio. Compared to the traditional speaker array, a high-end Ac2ated system might weigh about two pounds and takes up 0.04 cubic feet. The weight savings help all cars but electric cars especially. That Ac2ated draws less energy and that the system is less expensive than traditional speakers doesn’t hurt, either. And Continental is working on exterior sounds for electric vehicles where the sheetmetal would become the instrument.
Since we’ve all pulled up next to that car with the 22-inch subwoofer that rocks the neighborhood, we wondered: How does Ac2ated keep from vibrating a car to death? “It’s not that kind of shake,” Drescher said. The vibrations are barely detectable.
How soon will this future arrive? Drescher told us Continental is currently working with an OEM. Which one? She wouldn’t say. It’s a big secret. But by tweaking how we listen, Continental could help revolutionize the look and feel of the cockpit. Without the need for speaker grilles scattered about, designers get more freedom. “It’s a huge change for future interiors,” Dresher said. “We see these more clean, simple, minimal types of interiors coming.”
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