Laura McCreddie-Doak
Do you know what frequency your watch has? Can you work out from listening to it whether it’s a 18,000 vph model or a more spry 28,800 model? Frequency isn’t something talked about much. It might be there on the specs, but it isn’t something people immediately start explaining when they show off their latest acquisition. Except if it’s a hi-beat, that is. But what exactly does that mean and is it something to brag about?
What is a hi-beat watch?
Before we start comparing beats per hour, the first thing to cover is what a “frequency” is when talking about watches. Here that word refers to the number of oscillations the regulating organ – that’s hairspring and balance wheel – performs in a second, which is measured in hertz or Hz, or in an hour, which is when you see a much larger number, such as 21,600 and the letters vph (vibrations per hour) or bph (beats per hour).
A single oscillation is when the balance moves in one direction giving you the “tick”, then the other for the “tock”. Most watches run at between 2.5 and 4Hz or 18,000 to 28,800 vph, with the latter number being the most popular. There are some exceptions. For example, some of the Omegas that contain the Co-Axial movement, such as the current Seamaster 300m beats at 25,200 vph, while at the other end of the scale Grönefeld makes a watch that runs at 1Hz. However, generally speaking the majority of watches sit within that bracket of 2.5Hz and 4Hz.
The frequency of a watch can be directly related to the size of the balance wheel. The larger the balance the slower the oscillation, whereas a small balance makes things faster. That said, you can have large balance wheels that operate within the 2.5 to 4Hz bracket and some brands prefer them because they look better through a sapphire caseback. It also gives you the chance to admire the balance’s movement, rather than trying to follow the frenetic back and forth of a smaller wheel.
Hi-beat watches, as the name would suggest, are watches whose frequency is above 28,800 vph. The likes of Grand Seiko’s SLGH021, Longines’s Ultra-Chron and Zenith’s El Primero movement which all come in at 36,000 vph or 5Hz. Audemars Piguet’s Jules Audemars Chronometer goes in higher at 43,200 vph or 6Hz, and Zenith’s Defy Inventor clocks in at an astounding 129,600 vph or 18Hz. Generally the rule tends to be, the higher the beat, the higher the price. Interestingly though, during the period of experimentation in the 1960s and 1970s you could pick up a hi-beat for under £1,000. Before Seiko handed this technology over to Grand Seiko, chief among these was the Lord Marvel, which you can still pick up for around £260 on pre-owned sites.
Does it make a difference to accuracy?
Yes and no. There are many things that contribute to the accuracy, or rather timekeeping stability, of a watch. Temperature, shock, magnetism, not just the frequency. How well the watch is made is also a factor. Having a balance operate at a higher frequency puts strain on the movement, requiring it to have more durable parts and better lubrication. In other words, a hi-beat watch needs to be well-constructed in order to retain stability.
Because it needs to be better made, that means a better quality of oscillating system and, if the balance wheel isn’t perfectly balanced, higher frequencies help minimise the effects of gravity on the balance. One of the other ways in which having a high frequency helps to keep said frequency stable is impact recovery. Hi-beat watches recover faster from impact, so it takes less time to return to its functioning frequency.
However, hi-beats consume energy at a higher rate, meaning that the lever and escape wheel have more contact with each other. This increases the wear and tear on both parts, lowers the possible power reserve which means there is more need for maintenance. The other issue is regulating the movement. The escape wheel needs a lower inertia to oscillate at a high rate, this means it has to be small, which makes it difficult to regulate.
Hi-beats in chronographs – the two escapement solution
High-frequency chronographs are an interesting intellectual proposition. If you have a watch that’s running at 5Hz measuring tenths of a second, your chronograph will need to measure 100ths of a second. To achieve this you would have to fit the watch with a movement of 50 Hz, which would severely deplete the power reserve.
Luckily there is a solution, one that Guy Semon innovated when he was TAG Heuer’s head of haute horlorgerie back in 2011. Two escapements. In the Carrera Mikrograph 1/100th of a Second Chronograph, the timing function ran off an escapement with a frequency of 4Hz or 28,800 vph with a power reserve of 42 hours, while the chronograph escapement was 500Hz or 360,000 vph and had a power reserve of just 90 minutes if run continuously. This technology was adapted for the Zenith Defy 21, which has time keeping at 5Hz and its chronograph at 50Hz.
Grand Seiko mitigates this problem with its Dual Pulse Escapement, which delivers energy both indirectly, like a traditional Swiss lever escapement from the palettes and directly straight from the balance via a star-shaped gear mounted on the balance itself making the movement 20% more efficient. It maintains Grand Seiko’s strict +5/-3 seconds per day accuracy by having two barrels.
In many ways, buying a hi-beat watch for its promise of improved accuracy is rather like buying a tourbillon for the same reasons. It’s not really the point. High frequencies are something to talk about, to geek out on. Whether or not they get those -/+ daily rates down is almost beside the point.