This version is worn on a stainless steel bracelet with a folding clasp decorated with the Grand Seiko initials in 18k gold.Īs often with Grand Seiko, most of the beauty of the watch is to be seen on the dial, as once again the watchmaker has created a texture inspired by nature. Dimensions are still relatively reasonable, with a 40mm diameter and 11.8mm in height. Indeed, it features the same angular and redesigned case with a flat, straight brushed bezel, innard angle inside the lugs, polished accents on the sides and overall a more modern, less bulky design.
A quick look at it leaves no doubt on its lineage, being almost identical in shape with the SLGH005 White Birch. The Grand Seiko Minamo SLGA007įirst model in this new pair of Heritage Spring Drive models is named “Minamo” and goes under the reference SLGA007. The oscillator and sensor are vacuum-sealed into a single package to eliminate even the slightest temperature difference between the two and this shield also reduces the possible influence of humidity, static electricity or light interference and thus maintains the watch’s accuracy at the highest possible level. The Grand Seiko calibre 9RA2 Spring Drive, as seen in the Minamo SLGA007įor the first time in a Spring Drive movement, the IC incorporates a sensor to measure the temperature within the movement and is programmed to compensate for any inaccuracies in the crystal oscillation rate which may be caused by temperature change. While the previous generation of Spring Drive movements was given for an already impressive ☑5 seconds per month accuracy rate, Caliber 9RAX has an accuracy rate of ☑0 seconds per month thanks to a new IC package and to the selection of highly stable quartz oscillators that have gone through a three-month ageing process. The new Spring Drive 9RAX incorporates two barrels that deliver a power reserve of up to 120 hours – the so-called “Dual-size Barrels.” They are different sizes so as to deliver the torque required for the 5-day power reserve while optimizing the use of the limited space within the movement. Previous generations of Spring Drive movements were already delivering a comfortable 3-day or 72-hour power reserve – enough to leave the watch away for a weekend and still having it working on Monday morning.
This One-piece Center Bridge achieves a shock resistance. While slimmer, the Calibre 9RA5 has enhanced rigidity and shock resistance thanks to the new layout of the gear train towards the centre of the movement and a central bridge that holds them together. One of the key elements of this reduction of height is the re-positioning of the Magic Lever. Also, new construction of multiple parts has made possible to reduce the thickness from 5.8mm to 5.0mm. The new Calibre 9RA5 is, first of all, a brand new architecture with redesigned plates and bridges. The result: about 60% more power reserve, almost 1mm less in height, a much faster date mechanism and even better accuracy. It improves all elements – size, performance, decoration and functionality – and set a new standard for any spring-powered watch.
CALIBRE SPRINGS UPGRADE
The new 9RAX generation is a strong upgrade over existing movements, such as the 9R6x architecture. The result was a movement that looked almost identical to an automatic calibre, as still featuring multiple gears and wheels, just modified on the regulating part with an electronic regulator combined with a quartz crystal – the so-called “Tri-synchro regulator.” The 5-Day Spring Drive Calibre 9RA2 as seen through the caseback of the Tree-Rings SLGA008 On the second hand, it capitalizes on the proven accuracy of a quartz regulator – which is known to be far more precise than a traditional balance/escapement couple. On one side, it features a self-winding capacity to have perpetual energy (and no battery). One of the main differences between the 2020 Calibre 9RA5 and this new Calibre 9RA2 is the location of the power reserve indicator, here positioned on the back side of the movement for a cleaner display dial side.įirst and foremost, this movement is using the brand’s exclusive Spring Drive technology, a hybrid type of movement that capitalizes on the benefits of quartz regulation and the beauty and “perpetuity” of an automatic watch. And if the new 9RA2 is a development over this existing (yet recent) base calibre, it is the first time we see it moving into the Heritage collection, which necessitates to come back to what it means for the brand.
CALIBRE SPRINGS PROFESSIONAL
As such, this movement isn’t entirely new, as it is based on the same architecture as the 9RA5 that was first introduced on the Professional Diver 600m SLGA001 in early 2020.
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