Impedance refers to the headphone's nominal resistance to AC current, such as an audio signal.
Other things being equal, a higher impedance reduces distortion, but requires a more powerful amplifier — otherwise the headphones simply will not be able to produce sufficient volume. Thus, the choice of resistance depends primarily on which signal source you plan to connect the "ears". So, for a portable gadget (smartphone, pocket player), an indicator of
16 ohms or less is considered optimal,
17 – 32 ohms is not bad. Higher values —
33 – 64 ohms and
65 – 96 ohms — will require quite powerful amplifiers, like those used in computers and televisions. And models with a resistance of
96 – 250 ohms and
above are designed mainly for Hi-End audio equipment and professional use; for such cases, detailed recommendations for selection can be found in special sources.
The type of connector used to charge the built-in battery of the headphones, or more precisely, to connect an external charger. The role of such a device can be played by a network or car adapter, a power bank, or even a USB port of a PC or laptop (if there is an appropriate cable). At the same time, in true wireless models (there are
with a leg,
without a leg,
with an ear mount and
clips (Clip-on)), the "charger" cable is connected to a special docking station, where the "ears" are placed during charging (while the station itself usually has its own battery and can also work as an autonomous power bank). And in wireless and combined solutions of a more traditional design, the charging input is often located on the body of the headphones themselves. As for the connectors, the most common options are the following:
—
microUSB. A smaller version of the USB connector, created for portable devices. It appeared quite a long time ago, but it has not lost its popularity in our time, and is used by the absolute majority of manufacturers.
—
USB C. A miniature USB connector, positioned, among other things, as a potential successor to microUSB. Unlike its predecessor, it has a two-sided design, thanks to which the plug can be inserted into the socket from either
...side. It is still relatively rare, but the situation is likely to change in the coming years.
— Lightning. Apple's proprietary connector. Like USB C, it has a two-sided design, and is somewhat more convenient and reliable, but the use of Lightning is limited to products from Apple itself and its Beats brand.
