There’s plenty of conjecture online about the exact relationship between frequency, precision, and rate stability. And every time I think I have a solid understanding of the whose-its and whats-it of beats, balances, and the benefits of each, another question floats to the surface. Perhaps you feel likewise. So let’s try and break it down. (For the sake of this article’s length, we’re going to go ahead and skip over the quartz question, but you should know that a quartz crystal is indeed a mechanical oscillator, even if it’s battery-driven.) Ready? Here we go.

A watch’s frequency is determined by the total number of oscillations its regulating organ – the combined hairspring and balance wheel – performs over time. This information is typically shared in either the movement’s total Hertz (Hz), or in the exact number of vibrations/beats per hour (vph/bph).

If a mechanical watch ticks at 4 Hz or 28,800 vph/bph, that means the balance wheel is operating at four oscillations per second; a single oscillation translates to a total of two vibrations/beats per second. In other words, a vibration is counted when the balance moves in a single direction (tick), and an oscillation is counted once it’s moved and returned to its original position (tick, tock) – similar to a pendulum. Four oscillations per second equals eight vibrations/beats in the same period. There are 3,600 seconds in an hour, so simply multiply eight vibrations/beats by 3,600 seconds and you have 28,800 vph/bph.

The regulating organ of a watch functions with the escapement, which includes a movement’s pallet fork and escape wheel. With each beat of the balance, the pallet fork locks and unlocks the escape wheel. The kinetic energy created by the balance wheel, passed through the escape wheel to the fourth wheel, and drives the seconds hand on the dial itself. As you might expect, the balance loses a certain amount of energy with each beat, but the impulse created by the engagement of the teeth on the escape wheel and the pallet fork immediately restores the energy.

The mainspring houses energy as a watch is wound and gradually shares it with the gear train, which transfers that energy to the balance. The natural frequency at which a regulating organ runs controls how the energy is displayed as time on the dial. If you take a video of a mechanical watch and play it back in slow motion, you should be able to count how many ticks the seconds hand has per second – if a watch runs at 4 Hz, you’ll notice it ticks eight times every second. Pretty cool, right? This transfer of energy is the basis of how a mechanical watch tells time.

The frequency that a balance runs at is primarily determined by the design of the balance wheel and hairspring. Common sense indicates that the larger the balance, the slower it runs; the smaller the balance, the faster it’s able to tick. Additionally, the quality of a movement’s gear train has a direct impact on how smooth the seconds hand is. The finer the gears, the less backlash there is during the transfer of energy, and the smoother a seconds hand is represented on the dial. This is one area where you’re able to occasionally tell the difference between a higher-quality movement and one of lower standards.

So the frequency a watch runs at is fundamentally important, right? From a precision standpoint, yes, and the higher the better. It’s also important in that it’s integral to how a watch works, but the resonant frequency of a watch isn’t the only factor that determines precision.

For instance, many independent watchmakers prefer larger balance wheels that operate at 2.5 Hz or 3 Hz because they allow for greater visual stimulation for the owners of the watch, through an exhibition caseback. And it’s true – the more expansive a balance, the more eye-catching it tends to be rather than the flurry of hard-to-decipher action in a high-beat caliber. Movements running at a lower frequency have historically allowed for longer power reserves as well, given that the energy required in engaging with the balance wheel will be much less than what’s found in a high-beat caliber.

One important factor that governs precision is rate stability in the face of outside abnormalities such as temperature, magnetic fields, or external shocks, not just the amount of oscillations at which a mechanical watch runs. The quality of the watchmaking at hand is important, too.

The greater speed at which a balance oscillates means it will naturally be less responsive to outside disturbances, ergo it’s more precise. A balance beating more times per second is more stable, less influenced by external interference, and can recover from disturbances more quickly than a comparatively slower movement. Accordingly, high-beat watches are more precise for no reason other than they naturally are more resilient in their rate stability.

A watch running at 2.5 Hz that’s been manually adjusted “in X positions” (to account for positional variance on the wrist) and isochronism can easily deliver chronometer-level precision. A poorly regulated movement can be affected by all sorts of bumps in the night – regardless of frequency – but if it’s been effectively regulated by a watchmaker, then it will be better-suited for the motion of your wrist on a daily basis.

Isochronism measures precision as the mainspring goes through its various states of winding down. Think about it – when a mainspring is almost out of juice, it makes sense that there would be a less consistent transfer of energy from the barrel to the balance.

There is another noteworthy instance where a high-beat movement is always preferred, and that’s when it’s executed in chronograph form. A balance operating at a higher frequency will naturally allow for the more precise measurement of timing intervals given the very nature of the chronograph complication.

One of the primary issues that constrained the development of high-beat movements for years was the lack of appropriate materials and lubricants that could handle the faster design. The quicker a watch runs, the more wear each component receives. That means shorter service intervals and more headaches for watch brands and consumers. Zenith, for instance was unable to produce the high-beat 5 Hz El Primero chronograph movement until it got its hands on the Clinergic 21 escapement, built by Fabriques d’Assortiment Réunies in 1966, which increased the amount of teeth on the escape wheel to 21.

Twenty years later, when Rolex began using the El Primero inside the Daytona, it modified the movement to run at 4 Hz rather than 5 Hz. Although the technology was technically there to reach higher frequencies from the 1960s on, as seen by Zenith and Grand Seiko, many brands – like Rolex, which prizes itself on reliability – hesitated to embrace the tech. It really hasn’t been until the adoption of high-tech components like silicon, which are more resistant to general wear-and-tear, that high-frequency movements have been embraced on a large scale. Despite that, Rolex still has yet to use a movement running above 4 Hz.

You’ll also find watchmakers and companies doing different things for different reasons. The Swatch Group recently, and famously, adjusted the ETA 2824 from its original beat rate of 4 Hz to 3 Hz, in order to squeeze a greater power reserve, of up to 80 hours, out of it. After years of tinkering with the co-axial escapement, Omega’s watchmakers determined the optimal frequency to pair it with is the unconventional rate of 25,200 vph/bph.

As time has gone on, we’ve naturally seen more and more watch companies gravitate toward higher-frequency movements. The standard these days is typically considered 28,800 vph/bph, or 4 Hz, while 50 years ago, Seiko was describing that same operating frequency as “Hi-Beat.”

Jack recently wrote about how watchmaking today is largely defined by “incremental improvements” – he’s absolutely right. But one direction I would say we’ve seen more than “incremental” growth in is the standardization of certain materials leading to the democratization of high-beat movements. If a company wants to hit 5 Hz, it’s simpler than ever to get there.

So there’s no cut-and-dry answer. A watch’s frequency is simply part of the equation. If you’re the type of collector who gravitates toward old-world craftsmanship and appreciates knowing your watch has been adjusted by hand by a professional watchmaker, then you’ll likely prefer a timepiece that operates at a lower frequency. If you find yourself frequently intrigued by contemporary horological innovation, high-beat movements will likely be more of a fit for you.

A special thank you to Jack Forster and Nick Manousos for their knowledge and feedback.