Joining just seven previous models to have been given the Signature badge since Bowers & Wilkins started in 1966, reserving it for the rare and radically upgraded versions of its conventional loudspeakers and technologies. The most recent honour goes to two from the 800 D4 series - the 801 D4 and 805 D4.

The most apparent changes are the two special finishes: a stunning Midnight Blue Metallic and luxurious California Burl Gloss. The blue option (also previously only offered on the iconic Nautilus loudspeaker) features 11 coats of paint and lacquer that are machine and hand-polished to achieve the desired finish. The design is literally topped off with a bespoke blue Connolly leather top plate.

The California Burl Gloss finish is even more laborious as they work on showing off that fantastic wood veneer sustainably sourced from Italian specialist ALPI. Here, the cabinets receive at least 14 coats of lacquer in between multiple sanding processes. The finishing time for a single 801 D4 Signature cabinet in this finish is more than 24 hours, whereas the blue finish can be ready after a mere 18 hours.

While these beautiful finishes are the most noticeable upgrades from the standard offering, do not assume that these Signature D4s are simply cosmetic dressing, as the more you look, the more you notice that the engineers at Bower & Wilkins have had a hand in the new versions.

Firstly, both 800 Signature speakers enjoy a "radically enhanced" top plate that sits on a more skeletal, carefully damped, aluminium top panel designed to reduce unwanted resonances from the curved, already heavily braced plywood cabinets. This top panel sits below the Turbine Head on the 801 floorstanders and under the tweeter pod on the 805 standmounter.

Additionally, the speakers' reflex port is now cast from aluminium to create a structure that is said to be quieter than before. We're told that this results in cleaner and more accurate bass.

Furthermore, the drivers have also been given some Signature tuning. Granted, the 801 D4 Signature remains loaded with the 25mm Diamond dome tweeter, 15cm Continuum FST midrange and twin 25cm Aerofoil bass cones of the standard model; Bowers & Wilkins has worked its magic behind the scenes.

Of note is the new "FEA-optimised" mesh grille for the high-frequency unit, which is claimed to improve clarity. Lower down, the twin bass drivers feature upgraded motor systems. B&W has also redesigned the 801 D4's crossover, including upgraded bypass capacitors, to make the most of these revisions.

Similarly, as well as the improved top plate, the new 805 D4 Signature two-way standmounter also benefits from the more transparent tweeter grille, upgraded 16.5cm mid/bass driver motor system and an improved crossover network.

The Bowers & Wilkins 801 D4 and 805 D4 Signature speakers are available from selected dealers, with the 801 D4 Signature priced at £45,000/ €50,000 per pair and the 805 D4 Signature costing £10,000/ €12,000.

Visit Bowers & Wilkins for more information