Fiio f5 balanced iem earphones featuring infinity sound the fiio f5 earphones are balanced hi res in ear monitors with a balanced 25mm cable and an aerospace titanium diaphragm hi res audio certification the f5 has been certified by he japan audio society to be hi res audio capable this means that the f5 is capable of a frequency response up to 40khz which can fully reproduce the audio and give you a natural and life like listening experience that truly lets you listen to the music the way th