After four years of development and three generations of other product launch, countless experimentations and restarts, comes the FiiO FH15 IEM. Through objective data analysis and subjective listening tests, FiiO developed a brand-new 10mm dynamic driver with a carbon-based diaphragm. The result is a musical experience that feels like standing in the room with the artists themselves. The dynamic driver is built of thousands of stacked and woven cross-fiber carbon filaments. From the edge of the driver to the middle, these light and strong filaments move together as one for unbelievable fidelity. A trio of balanced armature drivers drives the middle and treble frequencies. These drivers work in conjunction with specially placed tuning holes in the shell of the FH15, delivering lusher vocals and airier details. The FH15 uses a specially designed resonator to enhance the volume of sounds between 1kHz and 4kHz, resulting in denser and more realistic vocals and instruments. The resonator is connected to a thin opening that interested unwanted resonance peaks and overlapping frequencies. The overall effect is better coherence among the drivers with a major reduction of sibilance. To prevent bloated and muddy mid frequencies, the FH15 filters the higher frequencies produced by the bass driver. This design reduces frequency response overlap between the bass and mid drivers for a much cleaner and natural sound. The FH15 comes with a 152-wire silver-plated monocrystalline copper cable featuring 8 strands of Litz-braided wire. The Litz braiding specifically reduces the skin and proximity effects, leading to reduced eddy current losses and thus improved high-frequency resolution. Additionally, the audio plugs are swappable, and included are 3.5mm/4.4mm plugs.