Comparison Audio-Technica ATH-M50x vs Audio-Technica ATH-M40x

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 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.

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.

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.

The total weight of the headphones; for true wireless models (see "Cable Type"), the weight of each individual earbud is listed.

This parameter is directly related to the design (see above) and some features of the functionality. Thus, the mentioned true wireless devices are very light, their weight does not exceed 25 g. More traditional in-ears and in-ears can be noticeably heavier, up to 50g for in-ears and up to 100g for most in-ears. Overhead models, for the most part, are quite massive: among them there are many models weighing 200 – 250 g, 250 – 300 g and even more than 300 g. It should be noted that a significant weight for false ears is often not a disadvantage, but an advantage: it allows them to stay on the head more securely, creates an impression of solidity and reliability, and most often does not create significant inconvenience.