The all-new FT5 is FiiO’s first planar magnetic headphones. Planar magnetic drivers are in between dynamic and electrostatic headphones. Like dynamic headphones, there is a sort of coil on the planar driver. Similar to electrostatic headphones, the diaphragm is a special kind of thin, micron-level film. The FT5 is 28nm chip-scale processed, leading to an approximately 6μm thick diaphragm. These characteristics of the planar driver make it possible to create a headphone that is not only highly detailed but also easy to power.
The FiiO FT5 employs an outstanding large 90mm planar magnetic driver. Compared to a traditional dynamic driver, a planar magnetic driver converts sound energy to sound waves in a more balanced way, by vibrating in a much more even way. The vibrations are distributed across the entire driver diaphragm and there is little distortion caused by the rigidity of the diaphragm material. Thus, the FiiO FT5 can truly and accurately express audio signals.
The FT5’s driver is both light and strong, allowing for a high sensitivity of 110dB/1Vrms@1kHz i.e. 96dB/mW@1kHz. This allows the FT5 to be easily driven even by portable players.
Full article: https://www.androidbrick.com/fiio-ft5/
You can’t tell based on specs. There are some extremely good headphones like Edition XS at this price point.