JVC HA-FXD60 / FXD70 / FXD80: The nanotube brothers

Disclaimer: These IEMs are owned by Dan. My apologies for being so late, my friend!
Insertion depth was right at the reference plane.

The diaphragm of JVC FXD-series IEMs is coated with a layer of carbon nanotubes, which are lighter than aluminium and twenty times stronger than steel according to the manufacturer. And the coating ultimately increases stiffness and shifts the diaphragm's natural frequency upward, resulting in a very tight control of sound.

On top of that, the top-of-the-line FXD80 is equipped with a brass cylinder and an acoustic damper made of glassfiber for increased acoustic damping.

PRO: Low distortion, extended bandwidth

CON: Interestingly, there is almost no difference between FXD60 and FXD80, in terms of electroacoustic performance. Rather, FXD60 is more tightly damped. On top of that, the rear vents only work as depressurizers only.

ON SECOND THOUGHT #1: Shallower insertion not only distribute the high frequency energy evenly here, it also extends the bandwidth slightly. It is evident that the JVC nanotubes are designed to be worn shallow.

ON SECOND THOUGHT #2: The frequency response of FXD brothers are far from the Olive-Welti target, as well as from the conventional diffuse-field reference.