4 years of Fine-Tuning Forging Ahead with the new reference grade hybrid

In 2018, FiiO implemented cutting-edge technologies such as the TRISHELL chassis, the S.Turbo acoustic design, and a 10mm polymer composite driver in the FH5, which gave listeners a rich yet detailed listening experience.
After the launch of the FH5, it was widely praised by users for its excellent deep bass and high-resolving ability in an affordable package. It has been on the market for over 50 months and is a testament to our dedication to great sound. The FH5 was also acknowledged by the industry-winning awards at the summer and winter 2019 VGP and in the 2020 VGP. In 2021, Fio launched the FH5s/FH5s Pro, with replaceable filters that allowed for more sound customization by the user. This time, we wanted to go back to the basics and take on the daunting challenge of bringing the sound quality of the FH series to new heights.

“VGP, standing for Visual Grand Prix, is an event organized by Japan’s Ongen Publishing. Beginning in 1984, over 30 years, the VGP has developed a reputation for being the “Oscars in the field of audio-visual equipment widely recognized in Japan and all of Asia. After four years of development and three generations of other product launches, countless experimentations and restarts emerged an IEM that is the result of innovation after a lengthy development process. Through much objective data and subjective listening tests, FiiO not only developed a brand-new 10mm dynamic driver with a carbon-based diaphragm but also combined it with other cutting-edge technologies in the FH15, which is designed to give you a musical experience as if you are there right with the artists.

Message from the engineers FiiO Present

Among our products, the FH5 is a mid-range product with a sound signature that’s agreeable to many. It features a rich sound with lush vocals perfect for detail-rich classical and instrumental music.
In the four years and 3 generations of product launches after the launch of the FH5, we found that users wanted brighter sound and even higher treble resolution but still maintained some of the FH5 sounds while being enjoyable for all kinds of music. Therefore, when designing the FH15 we took the sound of the FH5 as a reference when tuning and developing the drivers in the FH15. The lower frequencies are handled by our all-new 10mm dynamic driver with carbon-based diaphragm. The mid frequencies are produced by a custom Knowles ED BA driver, while the treble falls to the Knowles RAD for greatly improved transparency in the sound.
The bass, mids, and treble have been tuned in a way that allows the FH15 to sound great with all genres of music. For those wanting to precisely dial in the sound of instrumental music focusing on particular instruments such as the piano, guitar, violin, etc. the FH15 features interchangeable filters with distinctly different sounds.

Newly developed 10mm dynamic driver with carbon-based diaphragm

The FiiO development team chose to use carbon-based materials for the dynamic driver diaphragm, which allows for excellent transient performance. Carbon’s lightweight, strong rigidity and high internal resistance mean that the dynamic driver can quickly start and stop movements when responding to changes in the input signal. The high internal damping of the thousands of stacked and woven cross-fibre filaments of the carbon-based diaphragm means that the edge and the middle of the diaphragm can move together in the same direction quickly – minimizing the breakup of the driver that results when different parts of the driver do not move in synchronization. This results in less distortion and ultimately clearer sound.

Custom notch filter Richer sound for more pleasant listening

“For multi-driver hybrid earphones, combining them properly requires one to not only look at the drivers as a unit but also independently. We first tuned each driver separately as if they were on their own, and then scientifically combined the drivers. This methodical process allowed us to reach our sonic goals for the FH15.

The notch filter is specifically custom-made for the FH15 and gives it its distinctive sound: A Helmholtz resonator is designed to work with the mid-frequency ED drivers. When the sound wave is at a particular frequency that the Helmholtz resonator is designed to work with, the volume of sounds with this frequency is enhanced as the resonator concentrates and resonates that frequency. When looking at the frequency response curve, it can be seen that the response between 1 kHz and 4kHz has been improved, resulting in denser-sounding mids giving vocals and instruments more realism without sounding thin.

Additionally, the resonator is connected to a thin opening to eliminate any unwanted resonance peaks and overlapping frequencies produced by the different drivers, in order to achieve better coherency among the drivers while also eliminating sibilance. This is the notch filter technology employed in the FH15.