The FiiO F9 stands out due to its three drivers per channel. It features a dynamic driver that delivers rich and powerful bass down to the lowest frequencies, along with two balanced-armature drivers that ensure precise mids and highs. This design allows the FiiO F9 to cater specifically to the unique characteristics of different frequency ranges, providing a voluminous sound with high precision. The FiiO F9 is certified "Hi-Res AUDIO" by the Japan Audio Society and reaches frequencies up to 40 kHz, allowing music to be reproduced in its entirety, just as the artist intended.

The cable of the FiiO F9 is interchangeable and comes with two variants: a standard 3.5 mm headphone cable with an in-line remote for connecting to music players and smartphones, as well as a 2.5 mm balanced headphone cable for use with balanced outputs. The cable is designed to loop over the ear, providing additional support and comfort during extended wear. Also included are six pairs of ear tips in various sizes and a waterproof, sturdy case.

The design, inspired by water waves, is not only aesthetic but also gives the earphones high durability and maximizes internal space. The three drivers are well-protected and lined with plastic inside a premium aluminum housing, ensuring a long lifespan and preventing resonances. The FiiO F9 is a comfortable and thoughtfully designed in-ear headphone that delivers a sound with plenty of punch and precision.