Bulgari-Gérald Genta Collection: Octo Grande Sonnerie Tourbillon

Octo Grande Sonnerie Tourbillon is the ultimate embodiment of horological complexity, and all the more so in that the self-winding movement driving it is fitted with a Tourbillon regulator, a retrograde hour display, along with power reserve indicators for the movement and the striking mechanism. This exceptional movement, Calibre GG 31002, is an amazing distillate of excellence and symbolises several centuries of human and horological history.

The complexity of the twin-barrel movement naturally lies in the number of components: 863 in all. It is also symbolised by the internal organs dedicated to sound, or rather to the different types of sound that this musical work of art is capable of playing. For in this model, the supremely accomplished watchmaking art is matched by parameters specifically relating to the fields of metallurgy and acoustic science.

The gongs are made from a special steel alloy with a diameter similar to that of a piano string playing the high notes. The four gongs inside the Octo Grande Sonnerie Tourbillon are suspended between the movement and the inner surface of the case, thus enabling them to vibrate freely and to produce their sounds without any impediment. Each of them has a different length in order to produce its own specific sound, and each corresponds to a hammer that hits a specific spot on the gong. The rhythm, the speed and the strength of the strike are important in generating the purest and clearest sound possible.

Thanks to its 4 gongs, the Octo Grande Sonnerie Tourbillon is capable of playing the tune of Big Ben (Westminster/London). This authentic masterpiece can also perform two major audible functions: the Grande Sonnerie (grand strike) and Petite Sonnerie (small strike). In Grande Sonnerie mode, the mechanism strikes the hours, and then repeat the hour each time it is preparing to strike the following quarters – first, second and third – just like a clock tower bell. This striking mode known as “in passing” operates automatically, without any intervention by the owner of the watch. Meanwhile, the Petite Sonnerie mode also sounds the hour and the first, second and third quarters in passing.

One may of course also opt for the silence mode. And finally, the Repeater mode indicates the time whenever the wearer wishes by activating the repeater slide which triggers the striking mechanism. This mode is referred to as “on demand”.

The right-hand side (between 1 and 5 o’clock) of the dial with its alternating black lacquered, cloisonné segments, carries the strike/silent, striking-mechanism power reserve, time-indication power reserve and strike-mode selector (Grande/Petite Sonnerie) indications. It also accommodates the minute disc. Its left-hand side displays a retrograde hours indication. The white gold case is adorned with two beaded crowns serving to adjust the time functions (at 3 o’clock) and to activate the striking mechanism (at 9 o’clock).

This exceptional creation is all the rarer in that the watchmaker responsible for assembling its movement takes over a year to accomplish this daunting task.

Technical details
Self-winding movement, Grande Sonnerie Westminster Chime, retrograde hours display, power-reserve indicators, disc-type minutes display; 21,600 vph, 48-hour power reserve
43 mm white gold case, transparent caseback
18- carat white gold crown set with a falcon’s eye cabochon
Cloisonné dial
Water-resistant to 30 metres
Alligator leather strap, triple-blade folding clasp in 18-carat white gold


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