Let me show you the comparison between two models of wired headphones HIFIMAN HE400i vs Fostex T50RP MK3. They both are over-ear. Speaking of difference, the device made by HIFIMAN is open-back, while the other one is semi-open.
I offer you to start with some similarities in technical characteristics. Their sensitivity rate is only 1 dB different. HIFIMAN HE400i has 93 dB, while Fostex T50RP MK3 has 92 dB. When it comes to frequency response, the first appliance has a range of 20 Hz - 35 kHz, whilst the second one works in a range between 15 Hz and 35 kHz. Another point worth noting is the big distinction in the impedance since HIFIMAN's device has 35 Ohm, while Fostex T50RP MK3 has 50 Ohm.
The semi-open-back design of Fostex T50RP MK3 is a compromise between the airy, spacious sound of a fully open-back model and the superior isolation from environmental noise that a closed-back model provides. With these headphones, when playing complex musical works, when many instruments sound at the same time, it is possible to hear each of them separately, they do not drown each other out.
HIFIMAN HE400i offers you a clear and lively treble. In terms of the bass, you can get an amazing sense of lightness and realism as well as clarity of the sound.
Their physical characteristics are not special, as both devices have an adjustable headband and a detachable cable which is 150 cm and 120 cm long in the case with HIFIMAN HE400i and Fostex T50RP MK3 respectively.
Another factor to consider is that there is no microphone and built-in buttons. You will not have in-line control as well. Fostex T50RP MK3 vs HIFIMAN HE400i weighs 315 g and it makes the headphones lighter than the other ones. Comparatively, HIFIMAN's product is 370 heavy.
The Fostex T50RP MK3 is better headphones in this comparison. Check Fostex T50RP MK3 price