|
From YourSITE.com Audi News
The Danish hi-fi and electronics specialist Bang and Olufsen has developed a ground-breaking sound system for the Audi flagship model, the Audi A8, which sets a new benchmark even in the luxury car class. Audi will be presenting the series-production version of the “B and O Advanced Sound System” to the public for the first time at the 2005 Frankfurt Motor Show in the A8. The system can be ordered for all A8 models for € 6,000. An innovative design and advanced technology, along with the highest level of quality in materials and finish – these are the values embraced in equal measure by the cooperation partners Audi and Bang and Olufsen. The character of the Audi A8 as the sportiest saloon car in the luxury segment is defined by innovative styling and technology which embody automotive engineering at its most sophisticated. The aluminium body built according to the Audi Space Frame principle, quattro permanent four-wheel drive and the Multi Media Interface MMI are just three examples of Audi’s proverbial “Vorsprung durch Technik”. The Bang and Olufsen Advanced Sound System translates this technological lead into acoustic dimensions, too. This system, developed specially for the A8, takes into account the actual acoustic properties of the interior, such as dimensions, shape and the materials used. The sound tuning also takes account of engine, wind and road noises.
Specially developed for the Audi A8 are the speaker grilles made from meticulously crafted anodised aluminium – the same material used to produce the body of the sporty luxury saloon. The sound system is music to the listeners’ eyes: because its design is seamlessly integrated into the sporty, luxurious ambience of the A8, adding its own styling features.
When the system is activated, two lens tweeters are automatically extended from the dashboard. These ensure an extremely in-depth performance at every seat thanks to their precisely aligned horizontal transmission. Here the visual fascination of visible technology is combined with the acoustic brilliance of the new Bang & Olufsen Advanced Sound System. More than 1000 Watts on 14 channels
The Audi Advanced Sound System from B and O has 14 speakers. Each of the front doors incorporates a two-way speaker unit with a 90 mm mid-range speaker in a single housing with a volume of one litre, and a 140 mm woofer with a volume of 2.5 litres. The treble is reproduced by Acoustic Lens speakers that are extended out of the instrument panel. A 70 mm cone speaker serves as the centre speaker. There are two-way speakers installed in the rear doors. The 130 mm woofer has a volume of two litres and is supported by a 25 mm tweeter. The low bass tones are reproduced by a 200 mm subwoofer installed in a 10 litre housing. Together with two 70 mm wide-band loudspeakers for surround reproduction, it is installed beneath the rear shelf. The front tweeters using Acoustic Lens technology are among the most important elements of the new sound system. A dome with a high-attenuation, coated silk baffle emits sound into an ellipsoidal volume. The waves reflected by the wall of the ellipse all pass through the same focal point – hence the name "Acoustic Lens". Sound is projected evenly in a semi-circle in front of the speakers and not focused on a small area, as is usually the case with conventional tweeters. The way the sound is guided at the top helps to reduce the angle of vertical sound projection. This avoids earlier reflections by the windscreen.
The cleanness and transparency of reproduction are very important criteria for sound quality. It is important to avoid the various component signals being superimposed on one another during speaker decay. The problem is that speakers have a tendency to vibrate because they are spring-mass systems. However, they are held in check by the amplifier because the voltage generated during speaker decay is regulated by reverse coupling of the amplifier. In order to make this regulating process as precise as possible, the attenuation factor, in other words the ratio between the speaker's internal resistance and the output resistance of the amplifier, must be as high as possible. The 8 Ohm coil resistance (impedance) of the subwoofer realises very high values that result in an outstanding transient characteristic. One technical measure of cleanness is the degree of distortion. The magnet systems of speakers are fundamentally non-linear and thus generate anharmonic overtones. The subwoofer was optimised with a new simulation system. Distortion could thus be substantially reduced. So that these characteristics can be implemented in a stable manner, the speaker has a diecast aluminium basket and an extra-rigid paper baffle. Only the best materials are used for the other speakers as well, including rigid, high-attenuation carbon-fibre baffles, high-strength aluminium oscillation coils and ventilated Neodyn ring magnet systems. The two-component amplifier More than 1000 W is made available for the Audi Advanced Sound System on demand by two amplifiers. The high-performance amplifier has four channels of 125 W each for the four woofers and one 250 W amplifier for the subwoofer. The second amplifier (DSP) is responsible for signal processing and, with nine output stages of 35 Watts each, for energising the surround speakers and tweeters. Audio signal processing is performed purely digitally in the A8. In other words, the source data of a CD is transported to the DSP amplifier without loss of quality. Signal processing with frequency-response, phase-response and delay-time correction as well as level setting, dynamics influencing and surround sound are performed separately for each of the fourteen channels. This assures minimal channel crosstalk and optimum utilisation of the dynamics range of the DSP amplifier.
The developers attached particular importance to the calculation quality of surround sound. Today, most sound sources such as CD or DAB only have two programmed output channels (stereo); A8 drivers should nevertheless be able to enjoy the benefits of surround sound even when using these stereo sources. In addition, a special energising program calculates a surround signal with five channels and subwoofer signal from just two channels. A high-performance amplifier encounters unfavourable conditions in a motor vehicle because the installation space is severely limited, usually concealed behind trims, and the ambient temperature is often higher than 70°C. The amplifier's output of 750 Watts necessitated an entirely new switching technology. The so-called ICEpower amplifiers from B&O combine high thermal efficiency and extremely low frequency-dependent and load-dependent distortion. Tuning for clarity and resolution There is considerably more low-frequency than high-frequency interference noise in a vehicle. Therefore, unlike in the house, a linear frequency response is not the ideal solution. With the Advanced Sound System, the reproduction frequency response is adjusted according to the noise level so that interference noise can be fully compensated for. Interference noise is also subject to vehicle speed and road surface. Therefore, inside the vehicle, the overall signal comprises music, driving noise and passenger conversation. The interference noise is then filtered out, and at the same time, the music is adjusted. This dynamic modification of the frequency response enhances the sound quality considerably. A second important point is avoiding resonances. This is first because peaks in the frequency response are perceived as highly interfering, and second because the system is attenuation-equalized for a resonance, leaving a hum note during decay. This results in an unclean sound. The spatial representation of the music, or stage effect, is also very important. The task here is to compensate for various drawbacks of the vehicle interior: the listeners are seated asymmetrically in relation to the speakers, the listening space is very confined and a balanced surround audio experience is to be possible for both front and rear passengers.
The effect that music has also depends on the size of the performance area, for example the sound of an organ in a cathedral. To recreate this effect, a sufficiently large amount of early, directional reflections and an amount of late, diffuse reflections are added to the music. Surround sound in the vehicle is a new challenge: Audi does not regard the entire vehicle as a single listening zone. After all, in order to achieve an adequate surround level for the front speakers, the surround speakers would have to be set relatively loud. However, the rear passengers would then hear the music coming at them from behind, and who likes to sit with their back to the orchestra? Audi therefore operates with two surround listening zones: one for the front passengers and one for the rear passengers. This necessitates special allocation of the channels for the speakers and a suitable delay between the signals with the right low-pass filtering and level adjustment of the surround signal. A new quality of music reproduction has been achieved with the new technologies. Ample output for reproducing even the most complex of signals without distortion, in a controlled manner and with neat spatial progression. Also unique in the car hi-fi sector is the fact that this sound quality can be enjoyed equally at all seats in the A8, no matter how many occupants are present. “Vorsprung durch Technik” – for the A8 with the Advanced Sound System, this means no less than the world’s best mobile hi-fi system in the world’s best luxury-class saloon.
© Copyright 2004 by YourSITE.com |
