Impedance
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.
Frequency range
The range of audio frequencies that headphones can reproduce.
The wider this range — the more fully the headphones reproduce the spectrum of sound frequencies, the lower the likelihood that too low or too high frequencies will be inaccessible. However, some nuances should be taken into account here. First of all, we recall that the range of perception of the human ear is on average from 16 Hz to 22 kHz, and for the full picture it is enough that the headphones cover this range. However, modern models can noticeably go beyond these limits: in many devices, the lower threshold
does not exceed 15 Hz, or even
10 Hz, and the upper limit can reach
25 kHz,
30 kHz, and even
more. Such extensive ranges in themselves do not provide practical advantages, but they usually indicate a high class of headphones, and sometimes they are only given for promotional purposes.
The second important point is that an extensive frequency range in itself is not a guarantee of good sound: the sound quality also depends on a number of parameters, primarily the frequency response of the headphones.
Sensitivity
Rated headphone sensitivity. Technically, this is the volume at which they sound when a certain standard signal from the amplifier is connected to them. Thus, sensitivity is one of the parameters that determine the overall volume of the headphones: the higher it is, the louder the sound will be with the same input signal level and other things being equal. However, we must not forget that the volume level also depends on the resistance (impedance, see above); moreover, it is worth choosing “ears” for a specific device first by impedance, and only then by sensitivity. In this case, one parameter can be compensated for by another: for example, a model with high resistance and high sensitivity can work even on a relatively weak amplifier.
As for specific figures, headphones with indicators of 100 dB or less are designed mainly for use in a quiet environment (in some similar models, the sensitivity
does not exceed 90 dB). For use on the street, in transport and other similar conditions, it is desirable to have more sensitive headphones — about
101 – 105 dB, or even
110 dB. And in some models, this figure can reach
116 – 120 dB. and even
more.
It is also worth noting that this parameter is relevant only for a wired connection according to the analogue standard — for example, via a 3.5 mm mini-
...jack. When using digital interfaces like USB and wireless channels like Bluetooth, the sound is processed in the built-in headphone converter, and if you plan to mainly use this kind of application, you can not pay much attention to sensitivity.Speaker size
The diameter of the speaker installed in the headphones; models with multiple drivers (see "Number of drivers"), usually, the size of the largest speaker is taken into account, other dimensions can be specified in the notes.
In general, this parameter is relevant primarily for over-ear headphones (see "Design"). In them, emitters can have different sizes; the larger it is, the more saturated the sound is and the better the speaker reproduces the bass, however, large emitters have a corresponding effect on the dimensions, weight and price of the headphones. But in-ear "ears" and earbuds, by definition, have very small speakers, and rich bass in them is achieved due to other design features.
Volume control
The headphones have their own
volume control. Such a regulator can be placed both on the wire and on one of the cups (the latter is typical for wireless models). Anyway, this function allows you to easily adjust the volume: for this you do not need to go into the computer settings, press the buttons on the player or smartphone, etc., just use the control at hand. On the other hand, additional equipment complicates and increases the cost of the design, and also increases the likelihood of distortion. In light of the latter, volume control is almost never found in professional headphones.
Transparent mode
A feature that allows the user to hear the sounds of the surrounding world without removing the headphones.
This possibility is relevant mainly for models with a high degree of sound insulation; so the
transparent mode can be found mainly among in-ear models, as well as overhead "ears" of the Over Ear format in a closed acoustic design. A special microphone is responsible for the operation of the function, which “listens” to the surrounding sounds and broadcasts them to the headphones. In Talk Through mode, you can, for example, listen to the interlocutor or control the environment on a busy street. And some headphones with this feature also have more advanced functions, including automatic adjustment to the situation: such models turn on on their own to transmit speech, “hearing” the loud voice of a person nearby. Individual headphones react to loud street noises in the transparent Ambient Aware mode — it means broadcasting noises through the speaker that can be potential danger signals (screams, car signals, etc.).
Note that most models with Talk through also have an active noise reduction function (see above), and the “transparent mode” in them is one of the noise reduction modes. However, exceptions to this rule are possible — technically transparent mode does not have to be combined with noise reduction.
Voice assistant
Headphones with voice assistant support the user interaction with the device to a new level. The call of the
assistant. is carried out by pressing one of the control buttons on the headphones or by a specific voice command (for example, «Ok, Google» for the Google Assistant virtual apprentice). The assistant pauses playback, instantly changes the volume of the music, can notify the user of new alerts, helps to answer messages without the help of hands, and commands are given to the paired smartphone via voice control from the headphones.
Headphone battery capacity
The capacity of the battery installed in the headphones of the corresponding design (see "Power").
Theoretically, a higher capacity allows to achieve greater battery life, but in fact, the operating time also depends on the power consumption of the headphones — and it can be very different, depending on the characteristics and design features. So this parameter is secondary, and when choosing it is worth paying attention not so much to the battery capacity, but to the directly claimed operating time (see below).
Case battery capacity
The capacity of the battery installed in the case (case) for headphones.
This parameter is relevant only for true wireless models (see "Cable type"). Recall that these headphones are charged from a case, which is usually equipped with its own battery and actually works in standalone power bank mode. Knowing the capacity of the battery in the case and in the headphones, you can estimate how many charges of the “ears” will last for one charge of the case. However, it should be taken into account that in the process of charging the headphones, part of the energy is inevitably spent on third-party losses, and the effective capacity of the case turns out to be somewhere 1.6 times less than the claimed one. This is the starting point for calculations: for example, a 300 mAh case will actually be able to transfer 300 / 1.6 = 187 mAh of energy to the headphones, and 30 mAh “ears” from such a battery can be fully charged about 6 times (187 / 30 ≈ 6).
