Open (with no insulation) or closed (passive noise insulation) or semi-open (intermediate version). Open headphones sound more airy and provide a wide stage, closed ones provide noise isolation and amplify low frequencies.
Most of the headphones are dynamic but there are electrostatic, isodynamic, etc.
No higher than 32 Ohms for smartphone headphones. When using a good player or amplifier, it can be up to 100 Ohms. For stationary models you should coordinate the impedance with the amplifier power
More sensitive headphones will play louder than headphones with less sensitivity (with the same signal level and resistance)
A cable for a balanced (symmetrical) connection allows you to neutralize the negative impact of cable length on signal transmission, and also has a beneficial effect on the final sound.
The upper limit of the frequencies reproduced by the device. The human ear hears the standard frequency range: 20 Hz – 20000 Hz.
The length should allow you to lay the cable with a small margin. The longer the cable, the more impact it can have on the sound.
The size of the driver membrane
Headphone type: wired
In-Ear headphone type: with a wire
Kind of headphones: in-ear
Earpads material: silicone