The Way of Resonance

The first watchmaker who succeeded in incorporating the effect of resonance in a wristwatch was none other than François-Paul Journe. In 2000, he unveiled the Chronomètre à Résonance, which was inspired by Breguet’s No. 3177 clock which he had encountered during his time as a restorer.

Achieving the effect of resonance in a moving object such as a wristwatch is a considerable feat, particularly when it relies purely on the transmission of energy through a shared mainplate, without any mechanical linkage. The rates of both balances have to be adjusted as close to each other as possible while being free sprung, as having an index regulator reduces the effect of the vibration exerted on the mainplate. While Breguet noted that each balance had to be regulated to within a deviation of 20 seconds per day from the other, Journe found that they needed to be adjusted to within five seconds per day in a wristwatch because the driving force is smaller.

In the Chronomètre à Résonance, the crown at 12 o’clock winds both barrels simultaneously and each powers an independent gear train that drives a subsidiary time display on the dial. Notably, a rack attached to the balance cock enables the proximity of both balances to be adjusted.

The original Chronomètre à Résonance was produced from 2000 to 2019 before Journe introduced a new resonance movement, the caliber 1520, on the year of the watch’s 20th anniversary. In the new movement, the twin gear trains are driven by a single barrel, thanks to a differential which divides power to each train. Additionally, each gear train is now equipped with its own remontoir d’égalité that recharges every second to address the problem of unequal torque delivered to each balance as the mainspring unwinds. As a result, each balance achieves more constant amplitude and consequently a higher degree of rate stability. When in unison, these properties are heightened.