They’ve focused particularly on refinement. Minimising vibration across a broad frequency band was a major priority, so Audi ran programmes simulating the Cabrio body’s reaction to movements of the suspension and the mechanical assemblies. They even developed a special, low-vibration steering column with extra location provided by a support linked to the substantial cross-member below the windscreen.
Exceptional rigidity is a given for a modern performance cabrio but, even so, more than half the weight of the S4 Cabrio’s body-in-white is said to be accounted for by high-strength or extra-high-strength sheet metal. Stiffness is further bolstered by a rigid, bolted-on frame at the front with supporting diagonal struts front and rear.
Audi being Audi, you’d expect the cosmetic differentiation to be subtle, and it is. The front bumper has larger air inlets, the xenon headlights wear a titanium-coloured surround behind the glass and the aluminium-finish door mirrors are, of course, signatures of the S/RS models. Likewise, the broadly-spaced exhaust tailpipes and 18-inch cast aluminium Avus III alloy wheels wearing 235/40 R18 Continental Sport Contact 2 tyres.
Signifiers inside include a sexy, three-spoke leather-clad steering wheel, grey S-badged dials and, on our test car, brushed aluminium trim inlays (you can also choose carbonfibre, piano black, and birch finishes). It’s all so reassuring – from the secure swathe of wrap-around facia to the natural texture of the plastic binnacle enveloping the big, clear instruments. The substantial centre console is punctuated, in its upper quarter, with subtle, feel-good switchgear. Just as impressive are the sturdy armrests, the profusion of stowage trays and cubbies and supremely comfortable and supportive, electrically adjustable Alcantara/leather seats. Hardly a fresh approach, yet familiarity has not dulled the new S4’s enormous aesthetic appeal.
You have to count the electro-hydraulic soft-top as part of the appeal. Apart from looking great up and its 30 seconds of roadside kinetics, a heated, scratchproof glass window, triple-layer lining and smooth interior make it an utterly painless alternative to the saloon version.
As a major piece of hardware for shrinking the distance between A and B with maximum haste and minimum drama, the S4 saloon has few peers, though if driver involvement is a major factor, it’s slaughtered by the BMW M3. The Cabrio is more likeable, not least because of the better aural access to an engine worth hearing and, as is sometimes the case with well-executed soft tops, a more pliant ride.
Big-gun brawn remains the major draw, though, and the S4’s combination of explosive grunt and all-drive traction is formidable. Audi claims 0-62mph in 5.9sec, but it feels quicker, simply hurtling off the mark and sustaining a savage lick until well beyond 120mph.
But then the S4’s engine is a piece of work – superbly smooth and flexible, free-spinning and replete with the creamiest of V8 warbles. It feels instantly, almost fabulously, alert, though this is partly a consequence of the way the throttle response has been engineered. It’s very non-linear: hyper-energetic over initial inputs but comparatively flat through the remainder of its travel. It feels a little odd to begin with and, undeniably rapid as the S4 is, the subjective experience leaves you wanting more. As does the short-throw but oddly ‘disconnected’ feeling gearshift.
The feeling there should be more is also true of the chassis which, despite its weight-saving aluminium components, four-link front and trapezoidal-link rear suspension, is long on grip and stability but short on feel and adjustability. The Servotronic power steering is partly to blame. It varies the degree of power assistance with road speed, but feels too light up to about 50mph and disappointingly numb after that. At least it’s well-weighted and direct. And the front axle still has a small tendency to judder over sharp-edged surface deformations.
You don’t need to drive the S4 Cabrio back to back with its nemesis from BMW to realise that the Audi ultimately lacks the fluency and wide-ranging expression of the benchmark M3’s rear-drive chassis.But that won’t make it any less irresistible to some.
It may not be the definitive performance cabrio from the driver’s seat, but its 40-valve V8 is a superlatively smooth and muscular performer and its all-wheel-drive chassis tremendously grippy and passably agile. As an ownership proposition by any standards, though, it’s a hugely desirable car.