This reference has been fitted with three separate calibres during its production run. However, all three appear to have been based on the same ébauche – the Jaeger-LeCoultre 889, a popular base movement for multiple manufacturers during the ‘90s and ‘00s. Not only did Audemars Piguet use it, but so did IWC and Vacheron Constantin. It should be noted as well that Audemars Piguet owned 40% of Jaeger-LeCoultre up until the mid-2000s, when it was sold to the Richemont Group.
The three calibres houses in the 14790 are the 2125, 2225 and 2325. The earliest models hold the 2125, with the majority of them being equipped with the 2225. Only a few of the latest models came with the 2325 installed. These automatic date and time movements were also used in other Royal Oak references that were in production at the time.
We’re going to mainly focus on the 2225 movement here, as this is the one most commonly found in the reference. Measuring 26.6mm across and 3.25mm thick, it was equipped with a bidirectional self-winding rotor made from 21k gold. Running at 4 Hz (28,800 VpH), it gave 40 hours of power reserve and carried 36 jewels. When you look at this compared to its successor, the 2325, the differences are as follows: it carries 32 jewels with a unidirectional self-winding rotor, only powering the movement when it’s moving in a clockwise direction when looking from the dial side. It also goes down to a 38-hour power reserve – not a huge difference, but one wonders why this updated movement seemed to have a smaller reserve than the one it’s replacing.
What is good to know is that the 889 is still being produced, even if it is now the 889/2. This means that the spare parts for any 14790 movement are still readily available from the right sources.