ASSESSING cars is a tricky business because, no matter how analytical you are, there are many aspects that affect the overall enjoyment of a car that simply cannot be measured – like looks and feel and even sound.

In the case of the new Jaguar XKR, one of the most appealing characteristics is the engine note, a guttural roar when you open the throttle that excites and delights. If ever a Jaguar sounded like a jaguar, then this is it.

Blessed with an active exhaust system that controls the sound so that you can cruise in quiet comfort while still enjoying the aural delight under acceleration, this unmeasurable quality is a good reason on its own to buy the XKR – especially the convertible version.

Even hardened motoring writers on the press launch were seen playing with the throttle and trying to find tunnels to maximise the thrill of hearing this wonderful sound and some Jaguar folk are said to have it as their mobile phone ring tone. It’s that good.

The superb supercharged 4.2-litre V8 engine in the second-generation XKR has been around for a while now, but has been refined to produce a little more power (up 8kW to 306kW at 6250rpm)) and torque (up 7Nm to some 560Nm at 4000rpm) that gives it extra urge, especially in the mid-range.

Overall performance has really gained through a reduction in weight for the big cat, which benefits – as did the regular XK models introduced almost a year ago – from the introduction of an aluminium monocoque chassis in place of the previous steel chassis.

The result is a car that weighs between 70kg (coupe) and 100kg (coupe) than the previous model and is consequently faster off the mark and generally more agile.

Acceleration to 100km/h is quick if not breathtaking (5.2 seconds), but the mid-range response is very strong, making overtaking a breeze on country roads. Jaguar claims it takes only 2.5 seconds to race from 80 to 110km/h, which is 25 per cent faster than the regular non-supercharged XK.

There are faster coupes and convertibles on the road for those wanting that performance edge, but we never found ourselves wanting for more urge on a lengthy drive around the Hunter Valley.

Performance is aided by a sharper-changing six-speed ZF automatic transmission that was a delight to use.

One minute it provided seamless changes in keeping with a luxury cruiser and the next, with a jab of the throttle or by flicking it into Sport mode, the changing regime took on an extra urgency, snapping into the next gear or automatically double declutching down for a tight hairpin.

Driving the convertible is a sheer delight, even without the extra buffeting protection of the optional wind deflector. The wind is well controlled, there is no trouble holding a normal conversation and you get to hear that wonderful sound.

The structural integrity is superb, with no scuttle shake at all, even on rough roads, and only a mild amount of feedback through the steering to remind you that you are driving effectively a high-speed bathtub. There’s no reason to doubt Jaguar’s claims of high torsional rigidity.

Ride and handling levels, aided by Jag’s active suspension system, are superb. The Jaguar engineers have come up with a lovely balance between cornering performance, which is still very high and easily controllable while absorbing road irregularities with real poise.

With the roof up, there is no ‘booming’ and you never feel as though there is only a layer of material above your head.

Only a fairly high level of road noise spoils the driving experience, no doubt caused by those massive wheels and low-profile tyres. Such is the price of looking great.

The coupe is naturally much quieter inside, but there is still a fair bit of road noise and, of course, you do not get the same aural experience from the exhaust note.

Again, the ride is excellent and the ultimate grip level is probably higher than on the convertible if you are inclined to explore the outer limits.

The interior has a feeling of real quality, as you would expect, and we liked the contemporary feel of the aluminium weave panels, though more traditional Jag buyers might still prefer the burr walnut.

The seats are very supportive and have an enormous range of adjustment while the steering wheel has electric adjustment for both height and reach, so drivers of all sizes should be able to find the perfect seating position (provided they do not have a passenger trying to squeeze into the rear seat).