A mobile phone without a clock, camera and FM Radio is considered useless and so is a car without a music system. Necessities are transforming into luxuries. As high-end quality for listening pleasure is becoming increasingly important, Audi takes the lead in the advancement of this technology. Audi has successfully collaborated with suppliers Bang & Olufsen and Bose. Audi engineers, even independent of these partnerships, have established broad-based proprietary expertise. Read through for an insight into the next revolution in the hi-fi sector.

62 speakers in one car is the new Audi Sound Concept project headed by Peter Gleim. The engineer works in Infotainment Development at Audi in Ingolstadt and uses a Q7 for his experiments. Standard on the outside, interior modifications have transformed it into a rolling hi-fi studio that takes a radically new approach.

We have learnt in our schooldays that a sound wave can be recreated by a multiplicity of small sound sources placed closely adjacent to one another along the wave front. This principle was first put into practice in the late 1980s and can be experienced even today in a movie theatre in Ilmenau, Germany. Each of the 192 individual speakers at the Linden Lichtspiele movie theatre is driven separately by a fast computer – at the precise moment in which the virtual wave front would pass through its point in space. The result is fascinating: Each moviegoer experiences perfect audio spatialization in optimal sound.

Audi began its development work in collaboration with the IDMT five years ago. The current status of the project is the Q7 prototype. A powerful amplifier takes up most of the space in the luggage compartment, and thick cables connect it to three PCs. Installed in the Audi Q7 are 62 speakers – five woofers and five tweeters plus 52 mid-range speakers in the instrument panel beneath the windshield, in the roof pillars and in the doors. Five units each door sill with Audi-typical perfect workmanship.

Specialists made cut-outs in the sheet metal, fabricated new bezels and lowered the interior door release handles. “Prepare to be amazed,” says Gleim, as his eyes light up and he cranks up the volume. A sound like a thunderhead issues from the speakers an artful mix of music, traffic noise and animal sounds. Just imagine! Only the real worthy ones can get to experience such joy.

A female narrator guides the listener through the acoustic hubbub, dancing past the listener on the right and at other times on the left. The listener’s ears are forever surrounded by the sounds of driving cars and roaring lions. A marching band seems to march from side to side through the Q7 before finally a helicopter flies a lap around the cabin below the headliner.

“That is specially created wave field material,” says Gleim, “comprising up to 32 tracks, with specific spatial information for each of those tracks.” There are no corresponding audio media available on the market because there are no playback devices, either. A few film studios are already producing films with the method, however.”

You do not need special materials to demonstrate the effect of this wave field synthesis principle. Conventional stereo signals are more than enough to create entirely new acoustic images. The vocals come from far off, apparently from the workshop’s corner, and the guitar coming from the other corner. This impression is the same no matter where the listener is; behind the wheel or on the back right seat of the Audi Q7. The sound quality is always first class. Even the slightest buzz as the guitarist’s fingers hit the strings makes its way to the ear with extreme precision.

Audi had begun collaborating with the upscale American supplier Bose a good twenty years ago; the collaboration with Bang & Olufsen began around the turn of the millennium. Audi began offering the advanced sound system from the Danish sound wizards in the A8 luxury sedan in fall 2005. The 14 active speakers, including two acoustic lenses with anodized aluminium grilles, and 1,100 watts of amplifier power brought high-end sound to the automobile direct from the factory for the first time. The advanced sound system has a penetration rate of greater than 10 per cent in both models, the A8 and Q7, in which it is available.

For a new Audi model that is to be equipped with a new premium or advanced sound system, Audi engineers prepare precise requirement specifications in which the system layout – the type, number and installation location of the speakers, the speaker characteristics, the design of the amplifier and a target sound appropriate for the vehicle are defined.

Prototype vehicles are sent to Esslingen, Germany, and Struer, Denmark, where the partners work on the speakers, enclosures, amplifiers and acoustic algorithms. The last step is fine-tuning the sound, which is performed together with the Audi specialists in Ingolstadt. The “Sound Commission,” a body comprising representatives from all units of the company, is responsible for final acceptance and approval.

How close does the high-end sound in a new Audi A8 come to the reality of the recording? “The determining factors are always the installation locations in the car and the quality of the components,” explains Gleim. “When you order a car with the advanced sound system, you get the best speakers available anywhere. Many of them have membranes made of a fiberglass composite, which has a very natural and linear sound.”

The tight interiors will not allow the sound to spread out like in a living room. Cushions and upholstery absorb it, which is why the low frequencies must be overdriven to a certain extent. The electronic fine-tuning, that is, the tweaking of the algorithms in the sound processor handles this.

The laboratory features equipment valued at nearly €10 million, from the microphones and the special amplifier test bed custom-developed to Audi specifications to the laser vibrometer. The latter uses a laser to scan the surface vibrations that occur on the speaker membrane, the speaker housing or the door in which the speaker is installed.

The colour graphics produced precisely indicate if the membrane does not oscillate properly across its entire surface. “Weaknesses in a speaker are very often a simple question of design,” says Gleim’s colleague, Wolfram Jähn. “In many cases, the manufacturer can resolve these with minor changes, such as details of the curvature or the overlap between the paper and the rubber at the bead.”

Speakers are analyzed at the Audi sound laboratory in a testing room, which is a room-in-room construction. The testing room is mounted on thick elastomer bearings and is completely decoupled from the rest of the building, an absolute necessity given its direct proximity to a roller dynamometer. A floating wire lattice serves as the floor.

Human voices lose their richness in that room. The room is also often used to refine operating noises in the cabin, i.e., to fine tune clicking rotary knobs and switches. Whereas the testing room is used for mathematical analysis, the adjacent listening room is tailored for the subjective experience. It, too, is an acoustically optimized room-in-room construction – the special wooden double walls backed with insulation only allow the linear reflections desired. The precisely calibrated, high-end sound system installed here costs around €100,000 and its tube-based end stages are the size of small refrigerators.

Thanks to these detailed tests and comparisons, the sound development engineers at Audi can define detailed specifications for the speaker suppliers. Another element for success is the tight networking between Technical Development, Production and Quality Assurance at Audi. This enables requirements from daily production work and the real-world customer experience to flow into the development of new sound systems.