Why Beat Rate Matters: Understanding the Frequency of Seiko Movements

The beat rate, often expressed in vibrations per hour (vph) or Hertz (Hz), is a vital but often overlooked aspect of watch movement performance. This article aims to shed light on why beat rate matters and how it influences the behavior and character of Seiko movements, providing modders and collectors valuable insights into their timepieces.

What is Beat Rate?

In the world of horology, the beat rate is essentially the “heartbeat” of a mechanical watch. It describes how many times the balance wheel oscillates back and forth per hour, dictating the pace at which the escapement releases energy to the gear train.

  • Low Beat: Typically 18,000 to 21,600 vph (2.5 to 3 Hz)
  • High Beat: 28,800 vph or higher (4 Hz or higher)

Beat Rate and Accuracy

Contrary to popular belief, a higher beat rate doesn’t automatically imply better accuracy, although it can offer greater resistance to shocks and disturbances.

  • Isochronism: In the context of beat rate, isochronism refers to the movement’s ability to keep consistent time, regardless of the mainspring’s tension.
  • Stability: High-beat movements often exhibit greater stability against positional variations.

Seiko Movements: A Spectrum of Frequencies

Seiko’s wide range of movements offers various beat rates, catering to different needs and preferences.

  • 7S26: A low-beat movement operating at 21,600 vph, favored for its longevity.
  • NH35: Similar to the 7S26 but with hacking and hand-winding features, still at 21,600 vph.
  • Grand Seiko 9S85: A high-beat movement, ticking at a rapid 36,000 vph for exquisite precision.

Implications for Modders

For those involved in Seiko modding, understanding beat rates can have several practical applications:

  1. Component Compatibility: Components like pallet forks or escapement wheels may be designed for specific beat rates.
  2. Servicing: High-beat movements typically require more frequent servicing due to increased wear.


The beat rate is a crucial aspect that contributes to a movement’s performance, durability, and personality. Whether you’re a Seiko aficionado or an aspiring modder, understanding this nuanced aspect can offer a richer appreciation of the mechanics behind each tick of the second hand.

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