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 light weight, strong rigidity and high internal resistance means 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-fiber 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 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 Knowles BA drivers as if you were at the concert
For mid frequencies, the FH15 employs the custom Knowles ED-30262 BA drivers. These drivers work in conjunction with specially placed tuning holes in the shell of the FH15 which allows for lusher vocals and a more musical sound.
Treble is handled by 2 Knowles RAD-33518 BA drivers, which are capable of high treble resolution and capture every last detail in the music, for a truly airy sound. These drivers ensure that you get a listening experience as if you were there with the performing artists.
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 together. 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.
S.Turbo patented design
Scientific HiFi with optimized frequency response
Balance between bass, mids, and treble as well as clarity are the ideal sound goals of many audiophiles, but this is easier said than done with multi-driver hybrid IEMs. This is because the multiple drivers naturally produce frequencies that overlap and interfere with each other. Thus, crossovers that divide the frequencies to be produced between the drivers are needed in order to achieve clear, coherent sound.
Thus, the RC circuit design is used to manage the crossover in the higher frequencies, with the treble driver with the higher resonant frequency being used as the high-pass filter. For managing crossover of the lower frequencies, the traditional low-pass filtering LC circuit requires components that take up too much space in the naturally small in-ear monitors.
Come, let me be in charge of the sound
Interchangeable sound filters
3 pairs of audio filters are included, each pair allowing for a different sound depending on the density of materials within the filter:
Red filter—— enhanced bass, for a bold sound
Black filter—— balanced sound, transparent and clear
Green filter—— exquisite treble, highly resolving
*Green filters are pre-installed, the other filters are on the included storage sheet