Armin Strom’s first foray into the elusive world of resonance came in 2016 with the debut of the Mirrored Force Resonance. While it was neither the first wristwatch to demonstrate the phenomenon, nor the first to employ a coupling spring to the outer terminals of the hairsprings, it was the first to do so with a dynamically articulated clutch spring engineered specifically to regulate the transfer of vibrations between the two oscillators. The 43mm case housed a movement with twin gear trains designed to run in opposite directions, a configuration that promotes anti-phase synchronisation, which is known to be the most stable resonant state.
Though Armin Strom would go on to apply the concept to complications, most notably with the Minute Repeater Resonance, the architecture lends itself most naturally to a dual time function, where two independent going trains can be exploited to their fullest. In 2018, the Masterpiece 1 Dual Time Resonance was unveiled. It was a statement piece that looked as progressive as it was technically, housed in an oval case measuring 59mm by 43.4mm by 13mm. Its Brobdingnagian proportions gave it the air of a horological laboratory instrument rather than a conventional wristwatch, and it found its counterpoint last year, when the concept returned in a more wearable form — a round 39mm × 9.05mm case, the smallest resonance watch Armin Strom has produced to date.
This year, the brand introduced a monochromatic version in stainless steel. The Dual Time GMT Resonance Manufacture Black Edition features a pair black grené dials that matches its blackened main plate. While the most distinctive aspect of the calibre ARF22 is the resonance system, it is rich in other details as well.
Armin Strom Dual Time GMT Resonance Manufacture Black Edition (Image: Revolution ©)
At 12 o’clock on the face of the watch is an unusual winding click formed by a pair of ratchet wheel with vertically arranged teeth. The pair of wheels is linked to a pinion positioned between the twin barrels on the movement side. The upper ratchet wheel is held under tension by a helical spring positioned around the same axis. During winding, the spring flexes just enough to allow the upper wheel to lift and slip over the vertical teeth of the fixed lower wheel, advancing one step at a time. Each step delivers crisp tactile feedback, making the act of winding extremely satisfying.
Winding the watch is a visceral pleasure thanks to an unusual winding click at 6 o’clock made up of mating crown gears and a strong helical spring (Image: Revolution ©)
Since both barrels are wound in series via the crown on the right, a circular plaque is placed opposite the crown wheel to maintain visual symmetry. The layout of the movement is far more straightforward than that of the calibre ARF21 in the Mirrored Force Resonance. The earlier calibre had an intriguingly complex gear train arrangement to achieve a single off-centered time display, resulting in a thickness of 6.7mm. The Calibre ARF22, in contrast, measures just 4.92mm thick, with both gear trains laid out symmetrically with no overlapping beyond what is normal. Each gear train has its own dial with a day-and-night indicator that can be adjusted with its own crown on either side of the case.
Each display is individually adjusted via its own crown at 4 and 8 o’clock respectively (Image: Revolution ©)
Grené dials with integrated day-and-night indicators (Image: Revolution ©)
The watch in person is very impressive not just for its wearable size relative to the fact that it is essentially two movements in one watch but also for its aesthetics. There is a beautiful variety of finishing techniques. Each dial has a grené centre, with the outer black azurage chapter rings carrying the applied indices and printed minutes tracks. Just above the six o’clock position are the day-and-night indicators. Night is represented by a lunar surface, laser-engraved in relief, while day is depicted by black-polished sun rays set against a laser-darkened background. Though entirely monochromatic, there is a degree of elaboration in the finish that accentuates the architecture of the movement. Each spoke of the click wheel, for instance, has a satin finish across its sloped surface while the top surface is sharply defined and polished, creating a crisp contrast that highlights the unusual component.
(Image: Revolution ©)
On the back, the barrel bridge is decorated with Côtes de Genève, with jewels set in polished countersinks. The blackened base plate on the other hand has been laser-engraved with technical inscriptions outlining the specifications of the movement and the third wheels are supported by two frosted bridges. The openworked design of the bridges naturally lends itself to anglage, though the black coating renders such finishing more discreet. The most striking finishing is reserved for the centrepiece of the watch. A pair of mirror-polished steel bridges support the twin balance wheels while the element that sets the watch apart from resonance watches that came before and after — the spring bridge — is black polished.
The third wheels are each secured under their own bridges, which feature finely executed interior angles (Image: Revolution ©)
Both barrels are wound in series via the crown at 4 o’clock. Thus, to preserve visual symmetry, a plaque is mounted opposite the crown wheel (Image: Revolution ©)
How does resonance work?
Resonance in watchmaking refers to the tendency for two oscillators, be it pendulums or balance wheels, to synchronise their motion when they are mechanically or physically coupled. Though each oscillator is independently driven, a coupling medium such as a shared mainplate, bridge or spring enables energy exchange between them, allowing the system as a whole to settle into a stable, synchronised state.
The scientific basis lies in the principle that when two oscillators with nearly identical natural frequencies are coupled, energy begins to flow between them. In general physics, this interaction can cause both frequency and phase to adjust slightly until the oscillators align. However, in watchmaking, the frequency of a balance is a design specification and does not vary under coupling. Synchronisation manifests instead as alignment in amplitude and phase.
A common outcome of synchronisation is an anti-phase relationship, in which one balance swings to the left as the other swings to the right. While not strictly required for resonance, this configuration represents the most stable synchronised state for coupled oscillators, as it reduces energy loss. To further promote this, Armin Strom designed the gear trains to run in opposite directions, thereby predisposing the balances to oscillate in mirrored opposition.
One of the key benefits of resonance in watchmaking is improved stability. External disturbances such as shocks or positional changes may affect one oscillator more than the other. Through the coupling medium, these disturbances are partially absorbed or cancelled out, allowing the system to maintain more consistent timekeeping performance than a single oscillator operating in isolation.
What makes Armin Strom’s resonance different?
In the long and scattered history of resonance in horology, few approaches have been as explicit or structured as Armin Strom’s. Where past attempts, from Janvier and Breguet to Journe have relied on either incidental or passive coupling, primarily through the shared structure such as a main plate, Armin Strom has formalised the phenomenon through a compliant mechanism engineered to mediate and regulate the interaction between two balance wheels. It is a coupling system that does not simply promote resonance but also manages and sustains it by absorbing disturbances and facilitating resynchronisation.
Other modern interpretations include those by Haldimann and Vianney Halter, who placed twin balances within a shared tourbillon cage and linked the outer terminals of the hairsprings to enable mechanical coupling. However, at the heart of the Armin Strom resonance system is a dedicated component – a compliant mechanism referred to as a spring bridge. This is not a bridge in the traditional horological sense supporting a wheel or gear, but a flexible structure made of carbon steel. It is is anchored at both ends to a holding bracket, itself attached to the balance bridge. The hairspring studs are not fixed, as in traditional watches, but suspended along the spring bridge that spans both balances. A spring clip at the centre of the bridge allows the structure to pivot and stretch as it flexes outward during oscillation. This ensures that tension remains consistent throughout the cycle by compensating for the slight change in length.
The hairspring studs are suspended along the spring bridge spanning both balance wheels and a clip at the center of the spring allows it to pivot (Image: Revolution ©)
When the balances oscillate, always in opposite directions in Armin Strom’s configuration, the hairsprings exert force through their terminal curves, which are linked to this shared, elastic bridge. As the balances reach their maximum amplitudes at opposite extremes, the spring bridge flexes in one direction when the balances reach one end of their arc, and in the opposite direction when they reach the other. Crucially, if the balances are not oscillating in synchrony, this motion is uneven, and the spring bridge responds dynamically. One hairspring may be slightly ahead, the other slightly behind. In such cases, the bridge acts simultaneously as a brake and an accelerator, absorbing a fraction of the energy from the early-arriving spring and imparting that energy to the lagging one.
The mechanism thus acts as a corrective feedback system, continuously nudging the oscillators into synchrony. Over time, the balances naturally settle into anti-phase synchronisation, and the flexing of the bridge becomes symmetrical. At this point, energy transfer between the balances becomes stable, reinforcing their mutual rhythm.
(Image: Revolution ©)
Traditionally, resonance requires the rates of both balances to be meticulously adjusted within a very tight margin. Journe, for example, noted a threshold of 5 seconds per day for effective coupling in a wristwatch. In Armin Strom’s configuration, however, no such fine-tuning is necessary. The corrective action of the spring bridge allows the balances to start out with greater deviation, and the spring bridge will gradually align them through dynamic energy transfer. The mechanism is forgiving, but crucially, not imposing. It does not rigidly lock the balances together but allows them to self-regulate via mechanical interaction.
Synchronisation is not left to chance or confined to a narrow range of conditions. It is the result of an engineered bias designed to bring the balances into step reliably and repeatedly across all examples of the mechanism. It is also robust; synchronisation occurs quickly, often within minutes and holds under wrist borne conditions.
A resonance that is forced or emergent?
Now the elephant in the room is whether Armin Strom’s mechanism forces synchronisation, which overrides the very principle that makes resonance valuable. Forced synchronisation may look the same but it lacks the dynamic, self-regulating behaviour that defines true resonance. Disturbances are not absorbed or balanced, they’re simply imposed on the entire system. After all, Armin Strom’s system uses an overt coupling mechanism, deliberately engineered to drive the two balances into synchrony. But calling it “forced” mischaracterises the mechanical reality of what’s happening.
The crucial point is that the clutch spring is compliant. It detects and corrects discrepancies but doesn’t prevent them outright. It doesn’t rigidly constrain the balances or override their autonomy. Each balance is still independently driven by its own train and escapement. The spring is elastic so it merely facilitates energy transfer, absorbing slight timing differences and redistributing them in a way that leads the balances toward synchrony. Asynchronous motion is still possible and anticipated. If one balance gains or lags, the spring damps or boosts it subtly. Synchronisation then emerges from mutual adjustment through a shared elastic medium.
Hence, the mechanism doesn’t force resonance. It is assisting it with a system that makes synchronisation more robust, faster and less dependent on narrowly tuned if not nebulous conditions. The balances can still fall out of step under shock or drift and resynchronise on their own, which is the hallmark of true resonance.
Thus, Armin Strom’s system does not stand in contradiction to historical resonance mechanisms but in dialogue with them. It acknowledges the rarity and fragility of resonance as seen in Janvier’s clocks or Breguet’s pocket watches, and responds to it with piercing clarity. In short, it is a system that has been architected around resonance as a principle, and shaped to make that principle resilient, visible and demonstrably functional.
Armin Strom Dual Time GMT Resonance Manufacture Black Edition (Image: Revolution ©)
Tech Specs: Armin Strom Dual Time GMT Resonance Manufacture Black Edition
Reference: ST25-DT.90
Movement: Manual-winding Armin Strom manufacture Caliber ARF22; 42-hour power reserve; 3.5 Hz or 25,200 vph
Functions: Hours and minutes; dual-time display; day/night indicator
Case: 39mm × 9.05mm; stainless steel; 50m water resistance
Dial: Black grenage with black azurage chapter rings and applied polished indexes, polished and blackened steel day/night discs; rhodium, facetted and polished hands
Strap: Glossy taupe alligator strap with stainless steel pin buckle
Price: CHF 95,000
Availability: Limited to 50 pieces
