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  ... computer simulation software was used to optimise the body and chassis for its acoustics even before the first prototype vehicle was built.

Car audio systems are becoming more and more sophisticated.

But Mercedes-Benz is the first to consider the acoustics when building the body.

Since 2006 Benz has been working with American hi-fi company Harman to incorporate speaker chambers into the body in white. The result is the FrontBass system in the new SL due in Australia before the end of the year with prices from about a quarter to a half a million dollars. It will also be rolled out in future Benz models.

Harman used computer simulation software called Virtual Acoustics to optimise the body and chassis for its acoustics even before the first prototype vehicle was built. Harman senior acoustics expert Arndt Hensgens says they were able to evaluate it using binaural reproduction technology with engineers listening to the audio system in a "virtual SL".

"It meant that we were able to start with fine-tuning from a very high level with the first real prototype," he says.

The FrontBass system features two 150-watt woofers in the bulkhead of the car, using it as a resonator. It will be standard in the SL with the base audio system as well as an optional 600-watt, eight-speaker Harman Kardon Logic 7 audio system with 5.1 surround sound or a 900-watt, 12-speaker Bang and Olufsen system.

Hensgens says the project presented several challenges, including reserving the crash safety and stiffness of the chassis. He says the FrontBass system produces distortion-free bass that the driver and passenger can feel, but without the trim rattling as it does with other car bass speakers. It also means that reinforcements used in door-mounted speakers are not needed and placing the woofers in the footwell allows more space for other speakers around the cabin at optimum levels for the ear.

"This focuses the sound," says Hensgens. "Sound engineers are working under very tough conditions with open-top cars," he says. "With the roof down, virtually all resonance is destroyed. The music is literally blown away by the wind."

Another benefit is that the sound won't annoy passers-by when the roof is closed because there are no bass vibrations in the doors. Because the exhaust runs close to the bulkhead, the speakers are able to withstand up to 96C. They are also watertight and isolated from electro-magnetic interference.