Spiraling toward improved sound quality

  • 11-Apr-2008 02:58 EDT
Bowers&Wilkins 1.jpg

Sound-systems specialist Bowers & Wilkins'  spiral diffuser for automotive applications has six channels.

Consumer expectations with regard to in-car entertainment sound-reproduction quality has been heightened rapidly over the past decade, partly because of reduced noise levels in vehicles but also because of higher-quality home entertainment systems. To help to meet heightened standards, sound-reproduction specialist and Jaguar supplier Bowers & Wilkins has developed a new spiral diffuser tube designed to improve sound-system performance within the limited space generally available for speakers.

Not all sound generated by a speaker driver is good; unwanted sound emerging from the rear of a speaker cone may prove detrimental to that being emitted from the front, particularly in automotive applications when sound from the rear of a car speaker may bounce around inside door enclosures, creating delayed, resonant noise.

For home applications, Bowers & Wilkins uses a long, tapering tube behind the speaker to “soak up” unwanted sound. Vehicle packaging constraints make this a poor solution, but a space-saving technology used in its home theater system, the CT800, was found by the company to be suitable for low-profile automotive applications. The tube is replaced with a novel six-channel spiral diffuser that provides the 100-mm (3.9-in) tube length in only 10% of the depth.

“Each channel absorbs a portion of the unwanted sound energy from the back of the diaphragm,” said Martin Lindsay, Bowers & Wilkins Senior Automotive Business Manager. “The small depth permits us to use this technology even in very restricted areas, such as ‘A sails’ in doors where tweeters are traditionally located. We can advance performance across the range, even in high frequencies, improving clarity for piano, violin, and vocals.”

The patented spiral, visually similar to a turbine impeller, is typically made of injection-molded plastic and can be integrated into OE speaker designs. Its small size and low weight mean that vehicle manufacturers could apply it to existing platforms. In mid-range applications the diffuser design also offers significant structural benefits because the walls of the spiral tube can be used to augment the stiffness of trim, reducing panel vibration.

“The technology, coupled with our tuning expertise, offers a discernible improvement, removing unwanted noise and resulting in a much cleaner, crisper sound, without significant changes to the vehicle architecture,” Lindsay said.

Bowers & Wilkins’ Automotive Division recently announced its first production system with Jaguar, for the XF. The premium system was exclusively engineered into the new sedan from the concept stage, with specialists from the two companies seeking to optimize every aspect of the audio environment.

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