Comparison Sony WH-ULT900 vs Sony WH-XB910

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 sound 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, there are some nuances to consider here. First of all, let us remind you that the perceptual range of the human ear is on average from 16 Hz to 22 kHz, and for the complete picture it is enough for headphones to cover this range. However, modern models can significantly exceed these boundaries: 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 wide ranges in themselves do not provide practical advantages, but they usually indicate a high class of headphones, and are sometimes given only for advertising purposes.

The second important point is that a wide frequency range in itself is not a guarantee of good sound: sound quality also depends on a number of parameters, primarily the amplitude-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 ability to operate the functions and settings of headphones through a mobile application for a smartphone or tablet. Communication between the device and gadgets is usually carried out via the Bluetooth wireless protocol. The mobile application may provide tools for flexible sound settings (equalizer, bass boost, etc.), switching noise reduction and transparency modes, reassigning buttons and gestures, finding lost headphones, etc. Also, the ability to update the headphone firmware is often implemented through the mobile application.

Bass boost function for powerful and rich bass. Often implemented as a single button, with which you can actually "turn the bass on and off." Bass Boost is more convenient than adjusting low frequencies with an equalizer; in addition, various special technologies can be used to enhance the bass.

A function that allows you to automatically pause the playback track when you remove the headphones (or one headphone).

Autopause is found mainly in wireless models (see "Connection Type") true wireless format (see "Cable Type"); however, there are other types of headphones with this function — for example, with a combined connection and an overhead design. Anyway, the proximity sensor is usually responsible for the auto-pause operation, which is triggered when the earpiece moves away from the ear. This feature is especially useful in situations where, after removing the headphones, there is no time to manually pause playback — for example, you need to urgently respond to what is happening nearby. At the same time, some models are able to automatically resume playback when the earpiece is returned to its place, however, this function is not strictly required — it will not hurt to clarify its presence separately.

A system that reduces the influence of ambient noise on the audibility of sound through headphones. "Noise reduction" with the help of a separate microphone (or several micro) "listens" to external sounds and sends the same sounds to the headphones, but in antiphase. Due to this, the noise heard by the ears is attenuated almost to zero and the user can enjoy the sound of the headphones without interference even in a rather “loud” environment. For filtering in headphones, Active Noise Cancellation (ANC) and Environment Noise Cancellation (ENC) systems are used. The first suppresses all the noise around the listener, the second - reduces the noise level of the environment. Active noise cancellation affects the purity of the sound, but the noise from the outside spoils the picture when listening to audio tracks even more.

Also in the headphones there is an adaptive active noise reduction system Adaptive ANC, aimed at automatically adjusting the sound of the headphones depending on the level of ambient noise. In a noisy environment (for example, when traveling on the subway), the Adaptive ANC system enhances the work of “noise reduction”, in the absence of loud sounds from outside, it weakens the noise reduction.

NFC is a short-range wireless communication technology (up to 10 cm). One of the most popular ways to use this feature on your headphones is to automatically connect via Bluetooth (see "Connecting"). When these Bluetooth “ears” are brought near an NFC-compatible signal source (for example, a smartphone), the devices automatically recognize each other, configure the connection settings, and the user only has to confirm the connection. In addition, other options for using this technology may be provided — for example, automatic playback start when you bring headphones to the player.

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.