A slim microspeaker for smartwatches with a Halbach array magnetic circuit

In recent years, slimmer designs have been preferred for wearable devices for the sake of comfort and wearability. Thus, the width of mobile microspeaker devices is a critical constraint for smartwatches. In this study, we propose a novel microspeaker that achieves a 26% reduction in width compared to conventional models with an improved sound pressure level (SPL). The key difference lies in a new magnetic circuit structure inspired by the Halbach array, which enables a higher magnetic flux density through the coil and reduced yoke thickness. As a result, even though the total volume was 17% lower, the driving force factor, which is the product of the average magnetic flux density and the length of the coil, increased from 0.448 to 0.569 N/A. The experimental results showed an average improvement in SPL of 1 dB in the 300 Hz–1 kHz range. These findings validate the effectiveness and practicality of the proposed design.