[New for 2024] A deep dive into Grand Seiko Caliber 9SA4 models. You'll want to keep winding them!

We take a closer look at Grand Seiko's new model, the "Evolution 9 Collection Hand-Wound Mechanical Hi-Beat 36000 80 Hours Model," announced at Watches & Wonders Geneva 2024! This model is equipped with the newly developed hand-wound movement, Cal. 9SA4, and the winding feel of the mainspring is noteworthy.

Newly developed hand-wound movement Cal.9SA4

　When you get to the bottom of a wristwatch, which is an accessory, you start to pay attention to its "sensory performance," which cannot be measured by specifications. This is often felt through the feel of the watch when worn, including the balance of the center of gravity, and the feel of turning the hands, but in the case of a hand-wound watch, another important evaluation axis is added: the feel of the mainspring being wound.

　The Ref.SLGW003 and Ref.SLGW002 models of the "Evolution 9 Collection" unveiled by Grand Seiko at the recent Watches & Wonders Geneva are equipped with the newly developed hand-wound mechanical "Cal.9SA4," the first new movement in approximately 50 years. The base movement is the automatic "Cal.9SA5," and it shares many mechanical features, including a long power reserve of approximately 80 hours, an ultra-high beat rate of 36,000 vibrations per hour, as well as twin barrels, a hairspring, free-sprung balance, and a dual impulse escapement. The background to the development is that, during the planning stage of the Cal.9SA5,Mechanical chronograph Cal.9SC5It is included in the roadmap along with the 2021 model, and design actually began around 2021.

　The project began with the pursuit of elegance as a thin watch, in line with the Evolution 9 style. Manual winding was chosen as the means to achieve this. The Cal. 9SA5 is an "automatic winding with manual winding" movement, and it should have been easy to convert it to manual winding simply by removing the winding mechanism (in fact, there are many "manual winding specifications" with such designs). However, the design team was particular about the sensory performance of a manual winding watch. In other words, the winding feel was the most important thing.

Newly designed Kohaze

　The Caliber 9SA4 mainspring can be wound for approximately 80 hours with 54 rotations of the crown from a zero power reserve state. This is approximately 15% more efficient than the Caliber 9SA5. Furthermore, a newly designed recoil-type click mechanism achieves a comfortable clicking sound when winding, with just the right amount of crown weight and a pleasant sound. I normally use a Moritz Grossmann manual-winding watch, which also features a recoil-type click mechanism, and compared to that, the weight of the winding movement feels just right.

　Grand Seiko's design approach would have ruled out a retractable locking mechanism, which would have increased the number of parts and ultimately sacrificed robustness. Therefore, a new structure (currently patent pending) with enhanced durability has been adopted, bringing it closer to Grand Seiko's philosophy. Furthermore, in terms of exterior design, the movement designers apparently wanted to use a larger crown, but from the perspective of the design team, who wanted to pursue thin elegance, a crown that was too large was not desirable. It's this struggle that led to a rethinking of the manual winding mechanism, the design of the locking mechanism, and the size of the crown that makes me smile as a watch enthusiast.

Iwate's nature incorporated into design

　In terms of design, it seems Grand Seiko has made a point of keeping the first variations conservative. Therefore, the look of this model is based on the popular "birch dial" and is an even closer look. The former, which resembles a grove of birch trees, is commonly known as "white birch," while the latter, which emphasizes the bark of each individual tree, is apparently called "birchbark." Incidentally, the retreating kohaze (small sedge) incorporates the motif of the wagtail, a bird native to Iwate Prefecture.

　While the basic design is similar to that of the Caliber 9SA5, approximately 40% of the Caliber 9SA4 has been newly designed for manual winding. Because it is manual winding, the power reserve of approximately 80 hours is appropriate, preventing the mainspring from running out over a two-day weekend. However, I personally think that it could be shorter. Because, you know, it has a feel that makes you want to keep winding it!