Greubel Forsey Grande Sonnerie – Haute Horlogerie & Innovation At Their Best

The grande sonnerie and petite sonnerie hold a special place in the world of Haute Horlogerie. There are only a handful of watchmakers capable of manufacturing (and proposing in their catalogues) such works of arts, often regarded as the pinnacle of complicated watchmaking. Robert Greubel and Stephen Forsey have been contemplating this major endeavor for years, way before embarking on 11 years of research and development to finally present their own interpretation of this complication, a ‘sui generis’ creation that was without doubt one of the highlights of SIHH 2017.

The grande sonnerie is one of the most complex watch mechanisms (for more information about chiming watches, read our technical perspective here). Both the grande and petite sonnerie strike the hours and quarters in passing, though only the grande sonnerie repeats the hours at every quarter. Unsurprisingly, the interpretation of this complication by Greubel Forsey – the first chiming watch from the dynamic duo is unlike any other in horological history: a tour de force, boasting an uber-complex movement made of 855 parts (featuring several notable innovations), top-notch craftsmanship, superb acoustics and the inimitable Greubel Forsey style.

The Greubel Forsey Grande Sonnerie features a mode selector GS (Grande Sonnerie), PS (Petite Sonnerie) and SL (SiLence), all operated by the pusher at 4 o’clock. It is also a minute repeater, capable of chiming the time on demand at the press of pusher incorporated into the crown. The management of functions and power are critical in such mechanisms for all parts to interact simultaneously and strike the time indications perfectly all while managing energy consumption. The movement is powered by two energy sources: the first one for the chronometric part of the movement with two coaxial series-coupled fast-rotating barrels (one of which has a slipping spring – 72 hour power reserve). The second one for the power-hungry strike-work mechanism with a dedicated barrel wound by a platinum micro-rotor to fulfill its function for longer (20 hour power reserve).

The acoustics of the chime are remarkable, being loud and pure despite the fact that the watch is water resistant to 30m. The case is crafted in titanium, a metal with good resonating characteristics. The hammers strike on steel cathedral gongs. The silent speed regulating governor does away with any inelegant background noise. The striking is optimized without pause, eliminating the small silence generally perceptible between the chiming of hours and minutes.

The gongs; visible through the tourbillon aperture on the side of the case

Another remarkable and useful feat is the addition of 11 security devices. For instance, time setting is disconnected when chiming is in progress and during time-setting no chiming can be sounded. Indeed, striking watches require careful handling as inappropriate operations may damage the movement… and servicing such mechanisms is a long and complex process (the assembly of the movement requires months)!

To enhance the chronometric performance of the watch, Greubel Forsey is adding a 24-second inclined tourbillon to their impressive Grande Sonnerie. Naturally, it is up to the standards you have come to expect from the brand: 86 parts perfectly hand-finished and totaling just 0.37g, light alloy cage pillars, titanium cage bridges, gold counterweights, a variable inertia balance with gold screws, a hairspring with Philips terminal curve and Geneva-style stud… running at 21,600 vib/hour it is inclined at a 25° angle and rotates every 24 seconds.

The multilevel black dial is in the traditional Greubel Forsey style and shows the hours and minutes with the brand’s skeleton gold hands with arrow-shape luminescent tips. All applied indicators/markers are in gold. Around the dial, small seconds are shown at 6.30, the chronometric power reserve at 5, the strike-work power reserve at 2 and the strike mode selector at 3. A cut-out allows for the vewing of the hammers and the gongs.

Despite the complexity of its mechanism, the watch wears well as Greubel Forsey has managed to fit all 855 parts of the movement in its signature asymmetric case measuring 43.5mm in diameter and 16.13mm high (which is relatively compact). Crafted in titanium, it features a hand-satined case band and side window looking onto the tourbillon and steel cathedral gongs.

As always, the movement finishing is top-notch. Bridges are in nickel silver, frosted and spotted with relief engraved captions, the micro-rotor is black polished (also with relief engraved captions), the hammers are black-polished, the olive-domed jewels are fitted in gold chatons.

The Greubel Forsey Grande Sonnerie comes on a black hand-stitched alligator strap and is secured by a titanium folding buckle. Five to eight pieces of this timepiece will be manufactured a year, at a price of 1,150,000 Swiss Francs. For more information, visit www.greubelforsey.com.

Technical Specifications of the Greubel Forsey Grande Sonnerie

• Case: 43.5mm x 16.13mm – titanium – sapphire crystals at the front and at the back – lateral window in sapphire – 30m water resistant
• Movement: 36.40mm x 11.13mm – manual winding – 72h power reserve – 21,600 vibrations/h – 85 jewels –  hours, minutes, small seconds, petite et grande sonnerie, minute repeater on demand, striking mode selection, inclined tourbillon 24 seconds, movement power reserve indicator, strikework power reserve indicator.
• Strap : hand-sewn alligator with titanium folding clasp
• Price: 1,150,000 CHF