Are bigger headphone drivers better?

Not reliably. A larger diaphragm moves more air but is harder to keep rigid and control. The acoustic design around the driver — chamber volume, damping material, port geometry — shapes the sound far more than the diameter printed on the box.

Why it happens

Driver size is quoted because it is easy to measure and easy to market. What actually determines performance is how well the diaphragm holds its shape while accelerating: a larger one flexes more readily, which introduces distortion at exactly the frequencies it was made larger to reproduce.

That is why diaphragm coatings exist. Titanium, beryllium and biocellulose composites all raise stiffness without adding much mass, which matters more than raw area.

The enclosure does the rest. Chamber volume, the damping felt behind the driver, and the tuning ports together determine the frequency response you actually hear — and none of them appear on the specification sheet.