Sound

Concert hall on wheels

Ever since the introduction of the car radio, music and driving pleasure have gone hand in hand. The right soundtrack when you’re on the road has become an important consideration for drivers. But how do you ensure optimum audio quality within a relatively confined space?

By
Thaddeus Herrmann

“If it were up to me, I’d have the speakers positioned at ear height next to the windows,” says Wolfgang Zieglmeier with a laugh, knowing full well that this simply isn’t an option. Zieglmeier is a systems engineer in the field of acoustics and since 2004 has worked for Harman Kardon, an important and longstanding partner of BMW when it comes to high-end car sound systems. Since the arrival of the smartphone, music has played an even greater role in most people’s lives. And the more time you spend listening to music, the greater your appreciation of good sound: not just at home on the sofa, but in practically any situation – not least in the car. “At BMW we have long observed this trend – since the introduction of the CD changer, in fact,” says Thomas Würdinger, head of Audio and Entertainment at BMW. “That was the real turning point: the new technology demanded new solutions, something that wasn’t as crucial in the days of the radio-cassette player.”

“BMW realised early on that the sound experience has to be considered from the outset of a car’s conception. In effect, you have to make the speakers an integral component of the chassis.”

Dan Shepherd, Bowers & Wilkins

Concert hall sound: the High End Surround Sound System by Bang & Olufsen features 16 speakers, two central bass units and – in the BMW 5 Series, the X5 and X6 – output of 1,200 watts.

Calibrated for eternity

Acoustics is a complex science. We know that from our own experience in the home. Those new speakers may have sounded perfect during the demo at the hi-fi store, but when you set them up in your own living room it takes a great deal of time and effort to position them to reproduce the sound that persuaded you to buy them in the first place. Often the results are less than satisfying, but who’s going to start ripping out a wall to create the ideal space for a loudspeaker? Sound waves move about, are reflected and amplified by certain surfaces and absorbed by others. All that impacts on the way the music sounds, as does the position of the listener. Only when you’ve located the “sweet spot”can the music enjoyment really begin. “These are the same challenges we have learnt to deal with when it comes to a new BMW,” says Zieglmeier of Harman Kardon’s approach to creating sound systems for the car. When a new model is developed, he and his colleagues are on board from the word go, long before the first prototype is built. “But our great advantage is that we know early on where the speakers are going to be placed in the cabin and where there’s some leeway for adjusting their position. That allows the sound stage to be optimally calibrated and fine-tuned for the benefit of all passengers.” The positioning, dispersion angle, and even the number of often microscopically small holes in the speaker covers, are meticulously calculated by the designers, BMW’s own sound engineers and the teams from the loudspeaker manufacturers. It’s the only way to guarantee that the sound system really does deliver what the customer expects. “Awareness of quality sound in the car is growing,” notes Würdinger.

And BMW certainly delivers. For the high-end range, the company is currently collaborating with three audio manufacturers: Harman Kardon, Bang & Olufsen and Bowers & Wilkins. The latter’s audio specialists are responsible for the Diamond Surround Sound System that turns the new BMW 7 Series into a concert auditorium on wheels with its 16 speakers, 1,400 watts and ten-channel amplifier.

Together with its partners, BMW conducts elaborate tests aimed at achieving the perfect sound on wheels.

Standard equipment in the BMW i8 already includes seven speakers, all positioned to optimum effect for the passengers.

Standard equipment in the BMW i8 already includes seven speakers, all positioned to optimum effect for the passengers.

Diamonds, Kevlar and the Fibonacci sequence

Such specifications make for impressive reading, yet on their own they are no guarantee for a genuinely convincing sound at the wheel. “To integrate these technical components into the car in a meaningful way you need an open-minded and responsive partner, and that’s exactly what we’ve got in BMW,” says Dan Shepherd of Bowers & Wilkins. “BMW recognised early on that the sound experience has to be considered from the outset of a car’s conception. In effect, you have to make the speakers an integral component of the chassis. It’s the only way to avoid undesirable reverberations that distort the sound. And that is precisely what BMW is doing.” The subwoofer, for example, is positioned under the front seats rather than the boot, while the side speakers are directly attached to the bodyshell rather than being integrated in the cladding. “As an acclaimed hi-fi brand, Bowers & Wilkins produce the best reference speakers around the world,” Shepherd continues. “We apply the most innovative technology to continually raise the bar when it comes to natural music reproduction. Adapting this expertise for the new BMW 7 Series was an exciting challenge.” For the first time ever in automotive history, the sound system has tweeters made of synthetically manufactured diamonds. “We originally developed this process for reference speakers,” Shepherd points out. “Thanks to this technology we were able to raise the resonances far above the frequency spectrum audible to the human ear. That is crucially important in the car because vibrational interference is more likely to occur here. For the midrange units we used Kevlar. Having worked with the material in the hi-fi sector for more than 40 years, we’re very familiar with it and know exactly what its advantages are: crystal-clear voice reproduction. After all, what would music be without the human voice?” And it should come as no surprise that the perforation pattern in the speaker covers takes its cue from the Fibonacci sequence that is regarded as a natural constant in mathematics. Every detail counts.

The BMW portfolio now spans up to four different audio options. The standard sound system already has up to six loudspeakers, while the BMW i8 numbers seven. These systems are designed in-house by BMW, as is the first optional system offering customers hi-fi sound with up to 12 speakers. The third level takes the form of Harman Kardon’s Surround Sound System with a peak output of 600 watts distributed across up to 16 speakers. Bang & Olufsen, meanwhile, takes sound performance to impressive heights with its High End Surround Sound System featuring 16 speakers, 2 central bass units and – in the BMW 5 Series, the X5 and X6 – output of 1,200 watts.

The choice for the BMW 6 Series and 7 Series is somewhat different. The in-house hi-fi system comes as standard in these models, while those setting their sights higher can opt for the Harman Kardon Surround Sound System with up to 16 speakers (12 in the Convertible versions). Topping that is the High End Surround Sound System from Bang & Olufsen. Moreover, as an exclusive option for the new BMW 7 Series and the top-ranging audio choice for a BMW, there is also the Diamond Surround Sound System by Bowers & Wilkins boasting 1,400 watts. “That means we are able to offer the right solutions for all our customers according to their needs and expectations,” says BMW’s Thomas Würdinger.

China is streaming

Loudspeaker technology for the car is steadily improving. But the way in which music is consumed today is changing – with a shift away from the CD towards MP3 or streaming. That means data compression, compromised sound and loss of frequency ranges. In the light of these developments, do we really need a high-end sound system such as that in the new BMW 7 Series? “Needless to say we are responding to such trends,” replies Würdinger. “In China, for example, streaming is very popular among our customers. But if you’ve got a three-hour crawling commute through traffic jams over there, you want a sound system you can rely on.” The design and development of a sound system for the car doesn’t only depend on the audio components used and where they are placed, but also on the software that controls them and processes the music before it actually comes out of the loudspeakers. The goal is to get even compressed audio formats such as MP3 and streaming to sound as perfect as possible. “It’s all part of a big jigsaw puzzle,” explains Harman Kardon’s Wolfgang Zieglmeier. “Hardware efficiency and performance have improved, and you now get better quality for fewer watts. It sounds simple but it has to be developed from the ground up. You can control a great deal with software.” Bowers & Wilkins are going a step further: “A few years ago we set up the ‘Society of Sound’, a platform for all music lovers which we founded in partnership with Peter Gabriel and the London Symphony Orchestra,” says Dan Shepherd. “Members have access to uncompressed music, and owners of the new BMW 7 Series who opt for our system will find a USB stick in the glove compartment with a selection of the best music.”

As an option, the Harman Kardon Surround Sound System offers up to 16 loudspeakers. “That means we are able to offer the right solutions for all our customers according to their needs and expectations,” says BMW’s Thomas Würdinger.

07/29/2016