Creating a high-performance limousine like the Audi S8 to carry rear seat passengers far and fast in comfort is an even bigger ask than simply providing comfort for two in the front seats.
Pitch and yaw are uncomfortable to all occupants, which is why soft suspension should not be equated with good ride comfort. Less well understood is the fact that when the pivot centre of the chassis is too far forward, rear seat occupants will feel like they are on the end of a fairground seesaw every time the car changes direction.
So if you can marry good secondary ride with high speed body control, low roll angles, a well-placed dynamic pivot point and rear steering then the car will be able to proceed down a winding road without giving its occupants motion sickness.
As limousine owners will always be in the rear seat I make it a point to be driven in the back seat of any limousine on test. This has enabled me to benchmark the primary and secondary ride, seat comfort and cabin refinement of Audi, BMW and Mercedes flagship models for the last four decades.
Back seat driver
Over time the Mercedes S-Class has managed to retain the crown for secondary ride quality and low speed bump absorption, but they are not much fun to hustle rapidly down a winding road. The BMW 7-Series is more driver oriented and so more satisfying to drive, but less supple in the rear seat.
Meanwhile the Audi A8 and its S8 high performance variant has managed to position itself more or less in the middle of its two German stablemates, and is engaging to drive yet supremely comfortable in both front and rear. And until recently the Audi was the only one of the three to boast all-weather competence thanks to its quattro 4WD.
On the launch event of the current generation Audi S8 near Barcelona in November 2019, I was chauffeured from the airport to our lunch venue by a professional Audi race driver who conducted me rapidly along a 25km route encompassing a highway section, twisty coastal road, and some urban tarmac strewn with speed bumps.
This wide spectrum of very different roads underlined the total dominance of Audi’s predictive active suspension, making my journey in the back seat both enjoyable and eye-opening.
Most impressive was how well bumps at town speeds were smothered despite this test car wearing the optional 21-inch wheels. The active suspension nicely rounded off low-speed bumps, creating a ride as smooth as cashmere, while at high speeds the iron-fisted body control and distinct lack of roll in fast bends were the highlights. In this respect the S8 sits in the top rank for rear seat ride comfort, and also made me wonder how much more perceived comfort might be gained with the standard 20-inch wheels.
Sharp dressed man
Fast forward to 2023 and Audi’s high-performance flagship limousine is largely unchanged under its svelte aluminium skin, but now looks even more sharply dressed thanks to a recent facelift encompassing the front and rear bumpers, headlamps, radiator grille, and alloy wheels.
As before, predictive active suspension is standard equipment, the ‘eyes’ of the system being the front-facing cameras located in the top of the windscreen that scan the road ahead to discern speed bumps or other obstacles and feed the data to the ECU.
The computer then ascertains the distance to an obstacle such as a speed bump in milliseconds and raises the suspension by 50mm all round to provide maximum spring travel to take the sting out of a bump. While the system significantly ameliorates the effect of large long wave speed bumps, the short, sharp rubber speed bumps used in some parts of Spain delivered an audible ‘thump’ from the low-profile rubber. But this is more heard than felt.
The predictive active suspension is not a one trick pony and supreme ride quality is only one of its strengths. As we get older it becomes more of a chore to get in and out of low cars. The system addresses this by automatically raising the static ride height by 50mm to making ingress easier when you unlock the car and touch a door handle. When you stop the car and open a door the suspension rises again to help you alight, with the ride height returning to normal 10 seconds after the doors are closed and locked.
Suspended animation
The lateral forces caused by roll in corners are another source of discomfort for passengers, and this is addressed by the curve tilting function that leans the cars body into bends by up to three degrees. This function has the greatest effect at speeds between 80 and 130km/h, and lateral acceleration of up to 0.4g.
Meanwhile the dynamic all wheel steering turns the rear wheels in the opposing direction as the fronts to reduce the turning circle by up to 1.1 metres at parking speeds, allowing the LWB version of the flagship Audi to match the 11.4 metres turning circle of the much smaller A4. At speeds over 60kmh, the rear wheels can turn up to 1.5 degrees in the same direction as the fronts to effectively ‘lengthen’ the cars wheelbase for greater high-speed stability.
The speed with which these air suspension elements operate can only be achieved with 48-volt electric motors, which have far superior high current capability to a 12-volt system. This is the electrical equivalent of high torque in a car engine.
Audi’s version of the VW Group’s EA825 twin-turbo 3,996cc V8 that debuted in 2017 makes 571hp at 6,000rpm and 800Nm of torque from 2,000-4,500rpm. Thanks to quattro traction off the line the S8 is able to pull off a very rapid 0-100km/h time of 3.8 sec in normal wheelbase form, which bests its BMW and Mercedes rivals on the way to an electronically limited 250km/h top speed for both normal and LWB versions. Sadly there is no RS6 style optional Dynamic Package to extend this to 300km/h.
Dynamic excellence
On fast highway sweepers the S8 shows unerring stability and the ability to eat kilometres in total comfort, while its four-cylinder shut off mode makes a worthwhile contribution to fuel consumption on a light throttle cruise. In fact when I was not in a hurry and enabled the cylinder shut-off system as much as possible, I returned a 9.0 L/100km average, which is impressive for a 571hp limousine weighing 2,295kg!
The counterpoint is devastatingly rapid cross-country potential so long as the tarmac is wide like on the sweeping country roads between the Autobahn 8 and the Mindelheim area in deepest Bavaria. That said the rear steering helps on tighter bends more than you would think, as does the rear torque bias from the standard sport differential when you are pressing on in the bends.
While the S8 can waft you along in total comfort Audi has arranged things so that the singing voice of the bent-crank V8 comes through loud and clear under full throttle. With a first squeeze on the right pedal it reminds you that it has a genuine beating heart under the bonnet.
Calm and collected
The counterpoint is wafting along in virtual silence at 160km/h in the eighth ratio of the smooth Tiptronic transmission. These two extremes give the S8 a duality of character that borders on a split personality.
While a luxury car with a large cabin volume and low levels of mechanical and exterior noise intrusion is a good place to start, there are still many challenges for a car audio system to address. The biggest of these is the delivery of minimally compromised sound quality and imaging to each of the four seating positions.
More often than not a long wheelbase limousine tends to be chauffeur driven, so the sound imaging needs to be steered towards rear seat occupants. Conversely, when only the front seats are occupied, or just the driver is on board the sound field will be different again.
Private listening room
Aided by double glazing, the plush, well-insulated cabin is the perfect environment for a top-notch audio system like the Bang & Olufsen Advanced Sound System, which delivers 1,920 Watts from its 23-Channel Class D power amplifier into 17 speakers.
Another feature of the system is Vehicle Noise Compensation (VNC), which is able to detect and subtly compensate for exterior noises in terms of volume. When the noise is removed it will dial things back down again.
The piece de resistance is the Fraunhofer Symphonia 2.0 3D algorithm that uses an advanced DSP algorithm to create a 3D sound field for all occupants. This algorithm utilises the mid-range speakers and additional full-range drivers located in the A-pillars and the rear headliner to deliver a holographic sound field in which you perceive musical instruments and vocals with convincing depth, spread and height.
The B&O 3D Advanced Sound System has a pair of Acoustic Lens Technology (ALT) tweeters that pop up from the extreme corners of the dashboard. All the main speakers in the doors and rear shelf are self-contained and fire into the cabin. As they are not part of the cars structure they do not create unpleasant resonances at loud volumes or leak sound that would disturb people outside as you drive past.
The spread of speakers controlled by the 3D Sound technology can easily be optimised using the main touchscreen to adjust Focus, 3D Sound, Surround Level and the Speed Dependent Control settings.
The Focus control allows you to optimise sound distribution in All, Front, Rear and Movie modes, the last being used if you are playing a DVD or downloaded movie.
Tailored sound
The intensity of the 3D sound can be altered in discrete steps from Low, Medium, High and of course it can be turned Off. The Surround Level provides a horizontal fader control with settings from 0 to 18. Meanwhile, the VNC also uses a horizontal fader running from 0 to 24.
With decently dynamic music playing this B&O system proved to be convincingly musical with no vestiges of the bright, hard edged treble we experience with B&O systems in Audi, BMW and Mercedes models a few years ago that featured the first dashtop-mounted acoustic lens tweeters.
It has taken B&O’s engineers a while to fully master tuning of the sound processing system, but this latest flagship system has a good tonal balance and a spacious and engaging sound that you can enjoy whether your journey is short or long.
Conclusion: Audi S8 with B&O sound system
The latest facelifted S8 builds on the 2019 car with better looks, awesome straight-line speed, a class leading chassis and state-of-the-art interior. If we had to choose a fast and supremely comfortable car for a long trip in any weather, the Audi S8 would be at the top of our list.
- Price Audi S8: from around 151,300 euros
- Price Bang & Olufsen Advanced 3D Sound System: 5,300 euros
- More info: audi.com/
STEREO GUIDE Verdict
+ Excellent comfort, performance and driving dynamics
+ Cylinder shut-off delivers impressive fuel economy
+ B&O audio system is dynamic and immersive
- Lack of legacy USB-A input option is annoying
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Sound quality9.3
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Price/Performance sound system9.5
