The Grande Sonnerie, the most complex Greubel Forsey creation to date, and also their very first chiming complication was awarded the “Mechanical Exception” prize at the Grand Prix d’Horlogerie de Genève on November 9. Greubel Forsey’s winner is, in fact, a grande et petite sonnerie with minute repeater.
This achievement puts them in a very exclusive club of haute-horologists with such illustrious names as Patek Philippe, Audemars Piguet, Jaeger-LeCoultre, Philippe Dufour and F.P. Journe
“Conducting 11 years of research, assembling no less than 935 parts, filing two patents, incorporating Greubel Forsey’s third Fundamental Invention (Tourbillon 24 Secondes), developing an acoustic resonance cage generating an extreme purity of sound, installing eleven functional safety features ensuring unparalleled intuitive ease of use, performing a three-year wearing test… As highlighted by this only partial list of the stages involved, the creation of the Grande Sonnerie was indeed a monumental undertaking by Robert Greubel, Stephen Forsey and their team. This timepiece embodies the quintessence of their expertise and their idea of horological excellence,” reads a statement from the watchmaker, highlighting the dedication that has gone into realising the Grande Sonnerie.
A petite sonnerie or small strike watch chimes audibly whenever the hour hand passes over an hour marker. A grande sonnerie, or grand strike, on the other hand, chimes audibly on the hour as well as every quarter-hour. A minute repeater chimes every time the minuter hand passes over the minute marker. Separate tones are used to mark the hours, quarter hours, and minutes. These chimers were invented, in the late 1600s, to enable the time to be determined in the dark or to be used by the visually impaired.
Grande Sonnerie watches are significantly more complex than mere minute repeaters. One area of difference between the two lies in how they are powered. Both are driven by an independent spring barrel. However, the repeater’s spring is wound using a separate mechanism and is often short-lived. A grand strike watch, on the other hand, is usually wound using the crown as the spring barrel and is expected to power the chiming mechanism for at least a day.
The Greubel Forsey Grande Sonnerie is a petite sonnerie, and a minute repeater. Its grand strike mechanism is capable of generating 20 hours’ worth of power reserve which translates to 80 activations of the chime. To keep track of the power remaining in the springs, there is a “Reserve de Sonnerie” indication on the dial placed between the two and three-hour markers. Adjacent to it, at the three-hour marker, is a smaller gauge to indicate which chime mode has been selected. There are three modes: PS stands for petite sonnerie, GS stands for grande sonnerie, and SL stands for Silent mode. The chimes of the minute repeater can also be turned on or off as required.
The titanium acoustic resonance cage was developed inside the caseband itself, to provide the loudest possible volume which is produced by the one-piece double cathedral gongs that are visible through the tourbillon’s lateral window. The two striking hammers are visible on the dial side and feature flat black-polishing, hand bevelling and polished countersinks. The gold bridge supporting them is relief-engraved. The acoustics of this Grande Sonnerie is all the more impressive given that the timepiece is water-resistant to 30 metres.
The Grande Sonnerie also features the brand’s signature 24-seconds rotation Tourbillon. Greubel Forsey managed to incorporate all of these in an all-titanium case that is just 0.93 mm thicker, with a 43.5 mm diameter and 16.13 mm height, than a comparable and less complicated Tourbillon 24 Seconds.