Armin Strom Minute Repeater Resonance Masterpiece 2 (Part Two)

Armin Strom Minute Repeater Resonance (Part Two) – In this 3-part series, ESCAPEMENT goes behind the scenes and looks at the making of the base movement and minute repeater module.

Armin Strom Minute Repeater Resonance

Claude Greisler, the CEO and Technical Director of Armin Strom, was eager to create an extraordinary watch to mark the 10th anniversary of the company’s Manufacture. He found inspiration in Bern, the home of the Zytglogge. This thirteenth century clock incorporates automatons and mellifluously chimes the hours and quarters.

Greisler had the inspired idea to combine the brand’s impressive resonance system, a means of conferring amazing precision, with aural resonance using the age-old complication, a minute repeater. As Greisler explained to me during a recent visit to the Manufacture, ‘by combining two large complications, resonance and a minute repeater, we have created our first grand complication’.

As I mentioned in the first part of our 3-part series of features, Claude sought the help of his longtime friend, Alain Schiesser of Le Cercle des Horlogers. This specialist firm, located close to La Chaux-de-Fonds, the watchmaking capital of Switzerland, has much expertise in the making of minute repeaters.

Armin Strom Minute Repeater Resonance

A Manufacture par excellence

Unusually, Armin Strom is a Manufacture. While the number of companies possessing the necessary in-house expertise has grown in recent years, a significant number of watch brands still purchase generic movements from third parties.

Armin Strom Minute Repeater Resonance

Image – some components made by Armin Strom are incredibly small

At Armin Strom’s atelier in Biel, numerous components are made using high-tech equipment such as CNC machines, profile turning machines (bar milling) and wire erosion. The company makes all of the movement parts with the exception of the assortiment (escape wheel, lever and roller), balance wheel and hairspring.

Armin Strom Minute Repeater Resonance

Everything starts with the platine (bottom plate). It is cut from a square brass blank using a CNC machine and provides the chassis of the movement to which other components are affixed. Thereafter, bridges, wheels, pinions, pivots and screws are made to infinitesimal tolerances. Indeed, some parts are so small they are barely visible to the human eye.

Armin Strom Minute Repeater Resonance

Image – bevelling of a balance cock for Armin Strom Minute Repeater Resonance. Task undertaken at Armin Strom

After machining, components are entrusted to time-served hands which painstakingly bevel, engrave and polish the minute parts. The bottom plate is adorned with perlage and the bridges are embellished with Côtes de Geneve. The parts are then handed to the company’s in-house electroplating department. The brass and steel components are initially plated in gold prior to receiving an application of nickel. This process prevents corrosion and hardens the surfaces. Finally, the parts are dipped in the electroplating baths to imbue them with a particular colour. In the case of the Armin Strom Minute Repeater Resonance, the movement components are presented in ruthenium, imbuing them with a deep, rich, anthracite hue.

Armin Strom Minute Repeater Resonance

The movement is then passed to the watchmaker for assembly. Jewels are set into the base plate and bridges using a hand tool which pushes the jewel into its intended home. Once the jewels are set, the watchmaker adds the gear train and mainspring before adding the escapement and balance wheel. At this stage, the movement begins to pulse with life. However, just as the watchmaker sees the completion of the task on the horizon, he has to disassemble the watch, clean and dry each component prior to reassembly and lubrication as fine watchmaking etiquette dictates.

Armin Strom Minute Repeater Resonance

Once the watch is finally completed, it is tested over a number of days, ensuring the watch confers precision. It is only after this exhaustive process that a watch will leave the Armin Strom Manufacture in its presentation box.

The base movement

The Armin Strom Minute Repeater Resonance features the Manufacture Caliber ARR18. This consists of two elements, the base movement and the minute repeater module. Once the two elements are brought together, the movement measures 39.40mm x 11.35mm and is comprised of 408 components.

The base movement is made in Armin Strom’s Manufacture, prior to being passed to Le Cercle des Horlogers. Many of the parts used within the minute repeater module are made in Biel and transferred to the minute repeater specialist.

Armin Strom Minute Repeater Resonance

Looking closely at the base movement, it is actually not one movement but two. Each movement has its own regulator. Unusually, each independent mainspring is housed in one barrel and collectively they deliver 96 hours of autonomous operation. Each movement is hand wound, energised by turning the lone crown at 3 o’clock. The movements are vertically stacked.

At this juncture, many readers may wonder why the Armin Strom Minute Repeater Resonance contains two balance wheels. The model is equipped with an innovative resonance system which utilises two regulating organs, conferring several tangible benefits.

Base movement – resonance

Christiaan Huygens (1629-1695), the inventor of the pendulum clock and one of the most important figures in the field of horology, is said to have been the first person to witness resonance. He noticed that two separate pendulum clocks, when sharing a common beam, moved in synchronous motion.

Later, both Abraham-Louis Breguet (1747-1823) and Antide Janvier (1751-1855) would create double pendulum clocks. When two pendulums are subject to shock, one may slow down but the other will run faster by the same amount, minimising the effect of outside influence. Furthermore, both pendulums will ultimately return to a synchronous state. It is this phenomenon which Armin Strom has mastered and employed in several of its watches.

In the first part of our 3-part series of features, I discussed resonance and Armin Strom’s ingenious means of exploiting its benefits.

Both independent regulation systems are linked to a patented resonance clutch spring. The benefits of the resonance are threefold: a stabilising effect on timekeeping (better accuracy), conservation of energy and reducing the negative implications of shocks (better accuracy).

Armin Strom expended much effort refining the shape of the clutch spring in order to achieve resonance. It took Greisler three years to arrive at the optimum spring specification. However, his efforts were rewarded when CSEM, the independent Swiss research and technology organisation, confirmed that the two balance wheels linked by the patented clutch spring constitute a ‘true mechanical system’.

The resonance system conceived by Armin Strom should be viewed with the same reverence as the iconic tourbillon. In fact, Armin Strom’s system matches the accuracy of a tourbillon while delivering superior stability. Quite simply, the resonance system is a high complication.

Minute Repeater – introduction

In bygone times, before electric street lighting was commonplace, it was difficult to read the dial of a watch. The minute repeater allowed the owner, on demand, to hear the time through a series of chimes. These chimes would indicate the hours, quarters and minutes, merely by activating a push or slide-piece on the side of the case. Typically, minute repeaters chime three different sounds. Hours are normally signalled with a low tone, the quarter hours by a sequence of two tones and the minutes by a high tone.

Armin Strom Minute Repeater Resonance

Image – part complete minute repeater with no gongs

Usually, the sound is generated with two circular loops, formed of steel, termed ‘gongs’. These are struck by hammers to produce the desired sound. The strike mechanism of a minute repeater is formed of intricately shaped racks, snails, cams and wheels. The minute repeater is widely regarded as one of the most challenging complications to realise.

Minute Repeater module by Le Cercle des Horlogers

The first thing which is evident when looking at the minute repeater module fitted to the Armin Strom Minute Repeater Resonance is that the gongs do not conform to convention. The two gongs are an eccentric shape and exhibit a three-dimensional profile. The gongs are affixed to the case and movement with a ‘plot’.

Armin Strom Minute Repeater Resonance

Image – the unusually shaped gongs of the Armin Strom Minute Repeater Resonance

As the gongs emanate from the plot, they follow the contour of the dial and rise upwards, floating above the two regulator organs. This design invites the wearer to look closely at gongs, not just from above but also from the side. This characteristic is consistent with the brand’s message of ‘we show what we make’. Another benefit of this design is that the gongs sit close to the sapphire crystal enriching the sonorous voice of the watch.

Armin Strom Minute Repeater Resonance

Image – brass plate used for refining the profile of each metal wire

Making gongs is not for the fainthearted. A piece of steel wire is subject to repeated heating cycles and then skilfully formed by hand into the desired shape. A brass plate, machined using CNC at Armin Strom’s Biel HQ, features an outline of the gong and is used to fine-tune the gong’s contours. Schiesser himself makes all of the company’s gongs, expending numerous hours, painstakingly refining the profile of each metal wire.

Armin Strom Minute Repeater Resonance

Image – a gong with two parts of the plot shown

The two gongs are held within the aforementioned ‘plot’ (sometimes called the gong heel), but despite their close proximity, they never touch. The area of the gong adjacent to the plot is carefully filed to achieve the desired sound. Mere microns are removed from each gong. Should Schiesser remove too much material from the gongs, they would be rendered useless and discarded to waste. Thankfully, with years of experience, Schiesser seldom makes mistakes. It requires 30 operations to make a gong. Schiesser spent two months making the first five pairs of gongs. Perfection is never the product of haste.

The plot features three screws, two affix the plot to the base plate while the third connects the plot to the case. Incidentally, the case is made of titanium which, owing to its light mass, causes sound to resonate wonderfully, surpassing the performance of gold or platinum alternatives. The interior of the case is expertly designed to augment the richness and quality of the sound produced. While Greisler designs the exterior of the case, a specialist company is responsible for the case’s interior shape.   

When the fortunate wearer of an Armin Strom Minute Repeater Resonance actuates the chiming sequence, a dedicated mainspring is wound and each rack falls onto its respective snail. For example, the hour rack falls onto the hour snail, the quarter rack falls onto the quarter snail and, lastly, the seconds rack falls onto the seconds snail. When the racks have fallen onto their respective snails and the slide has been released, the watch is ready to chime.

Armin Strom Minute Repeater Resonance

Image – an undecorated rack

Le Cercle des Horlogers has equipped the Armin Strom Minute Repeater Resonance with a centrifugal governor. This device slows the rotational speed of the mainspring barrel, influencing the period of the chiming sequence. This reduction of the rotational speed is achieved by using two spring-loaded, weighted arms which extend outwards as the dedicated spring barrel unwinds. The extended arms create resistance, thereby reducing the rotational speed of the mainspring barrel. It is important that the tempo of the chiming sequence is not too fast or too slow. The chiming sequence of this new watch from Armin Strom lasts between 15 and 20 seconds.

Armin Strom Minute Repeater Resonance

Image – the centrifugal governor

Often when collectors discuss the sound of a minute repeater, they ask for ‘the best sound possible’. However, the sound of the hammers and gongs chiming the time is often a matter of personal preference. Schiesser’s vast experience confers a rich, vibrant tone, however, ultimately Serge Michel, Armin Strom’s Founder, has the final say about the resultant sound of the company’s latest creation.

Image – Serge Michel

The protracted creation of a minute repeater and the need to employ the most accomplished watchmakers means that this genre of watch are costly to produce.

Armin Strom Minute Repeater Resonance

Armin Strom Minute Repeater Resonance

Images – the centrifugal governor before and after fitting

Unfortunately, some owners of minute repeaters from competing brands have mishandled them, resulting in hefty repair bills. One mistake is to change the time indicated on the dial whilst the chiming sequence is taking place. Thankfully, Le Cercle des Horlogers has fitted the movement with a security system which prevents the wearer operating the minute repeater slide during time-setting and winding operations.

Minute Repeater – a collaborative effort

The base movement is supplied to Le Cercle des Horlogers by Armin Strom in part assembled form. Armin Strom fit the barrels, winding and hand-setting system and some parts of the gear train.

When the movement arrives at Le Cercle des Horlogers, the gear train is disassembled in order to fit a separate gear train for the minute repeater. The movement is then returned to Armin Strom for the resonance system to be fitted.

Armin Strom Minute Repeater Resonance

Image – Armin Strom watchmaker fitting resonance system prior to the movement being returned to Le Cercle des Horlogers

Thereafter, the movement is returned to Le Cercle des Horlogers for the gongs to be installed. The dial, hand-setting and encasing are also carried out.

Finally, the complete watch is returned to Biel where it is subject to quality control checks and rate testing.


The Armin Strom Minute Repeater Resonance is a paragon of fine watchmaking. It combines two high complications, making it worthy of the appellation, ‘Grand Complication’. However, judicious clients seeking the sweet sounds of a minute repeater also expect peerless finissage (finishing).

Armin Strom Minute Repeater Resonance

Image – hammers sometimes appear black, hence term black polishing but they can also exhibit a silvery, mirrored appearance from other angles. Task undertaken at Le Cercle des Horlogers

Armin Strom exceeds the expectations of the most discerning clients with finishing ‘to the very highest level’. The gongs are mirror polished (sometimes referred to as black polishing). This arduous technique requires a skilled worker to polish the component upon a tin plate in conjunction with diamond paste. Initially, a coarse grain paste is used, moving to a finer one at the end. It requires much time to achieve the desired result, but the mirror-like finish justifies the effort.

Armin Strom Minute Repeater Resonance

Image – the rack is drawn across an abrasive surface to impart a vertical grain to the component. Task undertaken at Le Cercle des Horlogers

Schiesser spends time polishing the gongs until they evince a brilliant gleam. Back at Armin Strom’s Manufacture, bridges are hand-bevelled and the patented resonance clutch spring is also mirror-polished.

Armin Strom Minute Repeater Resonance

Image – golden balance cocks before and after tremblage. Task undertaken at Armin Strom

The watch is endowed with two, large golden balance cocks which support the two oscillating balances. The surface of each balance cock is enriched with a sumptuous finish termed ‘tremblage’. This hand-engraving technique imbues the surface with a rich texture. Furthermore, the hand-crafted nature of the technique ensures no two balance cocks will ever be identical.

Armin Strom Minute Repeater Resonance

Image – the patented resonance clutch spring is enhanced with mirror polishing. Task undertaken at Armin Strom

The Armin Strom Minute Repeater Resonance harnesses exalted levels of craftsmanship with each component refined to the highest order.

The meaning of the word, ‘resonance’

When Armin Strom unveiled its first resonance watch, it used the word to describe two pendulums or regulating organs working in synchronicity. However, resonance clearly has long been associated with sound and the time-honoured complication, the minute repeater. Both the Biel-based Manufacture and Le Cercle des Horlogers are the respective masters of each field.

Most notably, there is a cultural resonance between Armin Strom and Le Cercle des Horlogers. They both show an amazing capacity to distill long-established ideas into horology applicable for today. Furthermore, each firm demonstrates an unwavering passion for excellence. Indeed, as this watch demonstrates, both companies have worked together in synchronous harmony for the benefit of Armin Strom’s loyal clientele, an achievement which will resonate will all horophiles.

Further reading

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