Comparison Hator Hypergang 2 vs HyperX Cloud Alpha S

In this paragraph, first of all, the method of mount on the ears is specified; according to this parameter, modern headphones are divided into overhead, earbuds, in- ear, glasses and headbands. For on-ear models, the acoustic design (closed, semi-open, open) can also be specified here, as well as the presence of such features as a full-dimensions (over-ear) design (in the absence of this feature, such headphones are called “on-ear”, or simply on-ears), swivel earcups, auto-adjust headband, or even the mid-2021 trend, Cat Ears. And details such as a rigid headband, behind-the- ear mount, mount on the neck and the ability to fold can be combined with almost any method of placement on the ears (with a few exceptions - for example, on-ear models are not attached to the neck).

Here is a more detailed description of the different ear placement options:

- Overhead. Overhead headphones are called headphones that are located outside the auricles, covering the ear from the side (“regular” overhead models) or completely (full-sized Over-Ear - see below about them). In any case, such models are quit...e large in dimensions. This, on the one hand, simplifies the creation of headphones with advanced sound characteristics, and also allows you to apply some specific tricks without much difficulty - for example, several emitters or support for multi-channel surround sound. On the other hand, the dimensions of the "ears" complicate the transportation and use on the go. In addition, it is worth considering that most overhead models have a headband, which is why they are poorly compatible with complex hairstyles and some headdresses. Models with rigid temples and behind-the-ear fasteners do not have this disadvantage, but they also have their own specifics (see below).
On-ear headphones can have different acoustic design:

• Closed. Models with a high degree of sound insulation, protecting the user from extraneous sounds as much as possible. This design contributes to a rich sound (especially in the bass range) as well as a very powerful immersion effect, making it well suited for home use (including computer games) and noisy environments. But it is not recommended to use such “ears” on the street: complete isolation from surrounding sounds in such conditions can be unsafe. In addition, it is believed that a completely closed design slightly degrades the sound fidelity.
• Open. Headphones with a minimum level of sound isolation, allowing most of the external sounds to pass through. They are inferior to closed ones in terms of power and saturation of sound, as well as efficiency in noisy environments; in addition, the sound from such headphones is well audible to others. On the other hand, open models generally provide more authentic sound and are better suited for situations where you need to control your surroundings, such as outdoor applications.
• Semi-open. A kind of compromise between the options described above: headphones with better sound insulation than in open models, but still not up to closed “ears” in this indicator. For some users, this middle option may turn out to be more comfortable. In addition, semi-open headphones are also appreciated in professional work with sound: they retain the richness of the bass and at the same time do not create the distortion typical of a completely closed design.
• With rigid shackle. Rigid headband allows you to securely fix the ear pads on the ears. A close analogue of the rigid headband is the headband of full-dimensions headphones, but in contrast to it, the headband is worn on the back of the head, and not on the top of the head. For this reason, hard temples are made mostly without padding, from bare plastic/metal. Headphones with a rigid headband most often have a sports focus, because the headphones, located on the back of the head, will not fidget on the head even with intense running. On-ear headphones are pressed tightly against the auricles, but the speakers themselves are placed on the outside of the auditory canals.
• Cat Ear ("ears"). On-ear headphones in an interesting design - with an imitation of cat ears on the headband. Such an addition does not affect performance, however, the "ears" look unusual and can be a great addition to the bright, original style of the owner. Cat Ear headphones are especially popular among teenagers.

- Intrachannel. Tiny earphones that, when used, are inserted directly into the ear canals. For ease of wearing, rubber or silicone pads are provided, often several of these pads are included in the kit to adjust to a specific ear dimensions. This design combines compactness and advanced performance: earbuds “ears” are often comparable to overhead ones in terms of sound volume and bass saturation, and the degree of sound insulation is very high (many models can even be used as impromptu earplugs). On the other hand, complete isolation from external sounds can sometimes be a disadvantage - for example, when cycling or walking along a busy street.

- Intracanal with a rigid shackle. In-ear headphones are laid inside the auditory canals, which allows them to be fixed as securely as possible in the ear and not fall off. The presence of a rigid bow further increases the reliability of fixing the headphones. This type of headphone is well suited for sports. The rigid headband and earbuds design of the sound emitters keep the earbuds securely in place even during intense running.

- Inserts. Also known colloquially as "pills". Similar to earbuds headphones, these headphones are small in dimensions and are placed in the auricle - however, not in the depth of the auditory canal, but at its very beginning, almost outside. This makes the earbuds somewhat simpler in design and cheaper, but it is more difficult to achieve rich sound and advanced acoustic characteristics in them. Such models give a rather low sound insulation, but this can be both a disadvantage and an advantage, depending on the situation. And some headphones of this type have an elongated shape, due to which they sit deeper in the ears and, in terms of their capabilities, can approach earbuds models.

Separately, it is worth noting that earbuds models and earbuds do not use headbands - the headphones are either completely separate or connected with a device such as a rigid headband or neck mount. So these headphones can be worn with almost any hairstyle or headdress without any problems.

— Inserts with a rigid headband. The earbuds are simply inserted into the passage of the auditory canal without penetrating deeply into it. This is not the most reliable way to fix the headphones, but due to the presence of a rigid headband, the earbuds gain a firm fit and a secure fit. The headphones themselves have an open sound path design, and therefore reproduce audio with a noticeable distortion of the original sound signal. But at the same time, the open acoustics scheme allows you to clearly hear what is happening in the surrounding space.

As for additional design features, they can be as follows:

- Full-dimensions Over-Ear. On-ear headphones (see above) in which each cup completely covers the ear and fits snugly to the head. The cups themselves in such models are made quite large and are equipped with characteristic soft "borders" around the perimeter of the inner side - these borders are adjacent to the head, so that the auricle is actually inside the cup. The main advantage of this design is that the headphones (with the right dimensions) practically do not touch the user's ears and do not put pressure on them - this is especially comfortable during prolonged use. In addition, it is easier to achieve high-quality sound insulation in Over-Ear models (although among them it is quite possible to find models with semi-open and even completely open acoustic design). The main disadvantage of such devices is bulkiness and inconvenience in transportation and use on the go. In addition, when wearing glasses, the Over-Ear cups usually press on the temples from the sides, which can cause discomfort.

- Auto headband adjustment. A headband that can automatically adjust to the dimensions of the user's head. Such a headband usually consists of two parts - a rigid, usually metal, base, and a soft inner part, which is adjacent directly to the head. It is the inner part that is able to stretch, and the user only needs to place the cups on the ears so that it is comfortable - and the headband itself will increase to the desired dimensions.

- Rigid bow. A shackle made of rigid material that connects both headphones and is located on the back of the head when worn; in some models it can also serve as a neck mount (see below). The advantage of such a device over the classic headband is that the bow can be used with almost any hairstyle and headgear. On the other hand, in earbuds models and earbuds (see above), this feature makes the headphones more bulky, and in over-ear models it makes sense to use it only with conventional models that are not related to full-dimensions Over Ear. Therefore, as well as for a number of other reasons, in our time the bow is not particularly popular.

- Ear mount. Attachment that allows you to fix each earpiece directly on the ear; as a rule, it has the appearance of a characteristic bow. This feature is found in all types of modern "ears", except for Over Ear (see above), and its specific meaning depends primarily on the main way the earpiece is placed on the ear. So, for earbuds models and earbuds, the behind-the-ear mount provides additional reliability of retention: the likelihood that the earpiece will fall out of the ear is reduced to almost zero due to such a retainer. In overhead "ears" this feature is much less common, and its main idea is to do without a headband or a rigid headband - in some cases, these design elements are redundant.

- Attachment to the neck. A feature that is found exclusively in wireless and combined models (see "Connection type") - and only earbuds and earbuds (see above). Both headphones in such models are connected to each other either with a regular wire with a thickened part, or with a special horseshoe-shaped hoop (a separate “ear” is connected to each end of such a hoop with a wire). In any case, when worn, such a wire or hoop is located at the back of the user's neck, which provides additional convenience: headphones removed from the ears (or dropped out) do not fall to the ground, but remain hanging on the mount. And in some models, special magnets are also provided, with which you can “stick” the headphones taken out of your ears to each other, turning the entire structure into a ring - this further reduces the risk of dropping the device.

- Possibility of folding. The earphones can be folded compactly for storage and transport. Note that this feature is indicated only for overhead models (see above) - earbuds headphones and earbuds are quite portable in themselves, there is no need to provide a special folding design for them.

- Swivel bowls. A design feature found in over-ear headphones (see above). Rotary in this case means bowls that, in the working position, can be rotated at a certain angle around the vertical axis. This allows the headphones to further adapt to the dimensions and shape of the user's head - which, in turn, increases comfort, especially when worn for a long time. On the other hand, the swivel mount somewhat complicates the design of the headphones, increases its cost and somewhat reduces reliability.

- Glasses. Headphones in the form factor of glasses. The sound of such models is transmitted either by directional speakers built into the temples, or directly to the inner ear by conduction through the bones of the skull. In addition to music, bone conduction glasses provide audibility of what is happening around.

- Headband. Headbands with built-in earphones. In a similar format, children's's models of headbands with bright prints of cartoon characters and fairy-tale characters are produced, as well as headbands for fans of a sports lifestyle. Headphones in such models are usually made removable, which allows you to wash the headband.

The specific connection interface provided in the headphones. At the same time, some models may provide several options at once - these are either combined devices (see “Connection type”) or wired headphones equipped with additional adapters.

— micro-Jack (2.5 mm). A wired connector similar to the popular mini-Jack 3.5 mm (see below), but smaller in dimensions. Equipment with such a connection is rare - they are mostly miniature devices, where there is simply no room for a 3.5 mm connector. Accordingly, this interface has not become widespread among headphones: it is almost never found in its pure form; models with such a plug are usually supplemented with an adapter or cable for a mini-Jack.

— mini-Jack(3.5 mm). Perhaps the most popular modern type of audio connector; If a device claims to have a headphone output, most likely it is a 3.5 mm jack. Accordingly, most headphones with a wired connection use this type of connector. It is worth noting that headphones with a microphone designed for such a connection are equipped with a special plug for a combined headphone + microphone audio connector (similar connectors are popular in portable gadgets and laptops). But with a jack intended only for “ears” without a microphone, such a plug may not work correctly. An alternative could be headphones equipped with two separate mini-jack plugs; See below for more details on this option.

— mini-Jack (2 x 3.5 mm).... Models with two 3.5 mm mini-jack plugs. This option is guaranteed to mean that we are not talking about classic headphones, but about a headset with a microphone: one plug is used for headphones, the second for a microphone. Such models are convenient when used with equipment that has separate 3.5 mm jacks for “ears” and a microphone - for example, for a PC.

— Pentaconn (4.4 mm). It is a 5-pin balanced output. Pentaconn uses a larger plug compared to the mini-Jack; its size is 4.4 mm, which is stronger and more reliable than the 3.5 mm connection. Pentaconn's balanced connection makes it possible to work with high-power audio signals. Thanks to this connection, it is possible to transmit a signal over a fairly long distance. Accordingly, such a connector is relevant for headphones of the highest category.

— Jack (6.35 mm). The largest type of Jack-type audio connector found in modern technology. Outputs of this type are found mainly in stationary audio equipment - for portable devices they are too bulky, where it is easier to use a 3.5 mm mini-jack. At the same time, the 6.35 mm connector is considered a more suitable interface for professional and audiophile-grade equipment: it provides a more reliable connection, greater contact density and, accordingly, less likelihood of interference. Therefore, although relatively few headphones (mostly premium solutions) are equipped with their own Jack type connector, many models with a 3.5 mm mini-Jack plug are equipped with an adapter to 6.35 mm.

- XLR. A characteristic round connector with a locking lock and 3 contacts (there are other options for quantity). Typically, it is used to transmit an analog signal over a balanced connection. This connection provides high immunity to interference, typical for professional use; at the same time, the connector itself has quite large dimensions. In view of all this, the presence of XLR is relevant mainly for headphones designed for use with advanced stationary equipment.

— Bluetooth. The most popular wireless connection option in modern headphones. This is due to the fact that built-in Bluetooth modules are available in almost any modern smartphone, tablet or laptop, and appropriate adapters can be produced for devices without this module (for example, a PC). True, the sound quality with a traditional Bluetooth connection is relatively low, but to correct the situation, special technologies like aptX and aptxHD are increasingly being used (see “Codec support”).
It is also worth noting that Bluetooth modules can correspond to different versions (the latest for 2022 are Bluetooth 5.0, Bluetooth 5.1, Bluetooth 5.2, Bluetooth 5.3, Bluetooth 5.4). This point does not affect the sound quality, but it determines a number of additional nuances - communication range and reliability , the ability to work through walls and other obstacles, resistance to interference, etc. In modern “ears” you can find the following versions of Bluetooth:

• Bluetooth v 4.0. An update in which the capabilities of version 3.0 (classic + high-speed Bluetooth) were supplemented with a third format - Bluetooth LE (low energy consumption). This communication standard is intended mainly for transmitting small amounts of information - in particular, service data packets to maintain a connection. At the same time, the creators managed to combine economical energy consumption and a long communication range - it can reach 100 m. This has a positive effect on the stability of the connection.
• Bluetooth v4.1. Development and improvement of Bluetooth 4.0. If we talk specifically about headphones, the key innovation for them in this version is improved noise immunity when working near 4G (LTE) mobile communication devices (in earlier standards, Bluetooth and LTE signals could overlap, which led to failures). So, for use with a 4G smartphone, headphones with Bluetooth support of at least v 4.1 are definitely recommended.
• Bluetooth v4.2. Further, after 4.1, development of the Bluetooth standard, which mainly introduced a number of general improvements in reliability and noise immunity.
• Bluetooth v 5.0. Major Bluetooth update released in 2016. One of the most notable innovations was the introduction of two additional operating modes of Bluetooth LE: an increased speed mode (by reducing the range) and an extended range mode (by reducing the speed). In the case of headphones, the main significance of these innovations is to improve the overall reliability of the connection, increase its range and reduce the number of dropouts.
• Bluetooth v5.1. Update version v 5.0, in which, in addition to general improvements in the quality and reliability of communication, an interesting feature has appeared, such as determining the direction from which the Bluetooth signal is coming. Thanks to this, a smartphone or other gadget that supports this standard is able to determine the location of connected devices with an accuracy of a centimeter; This can be useful, for example, for finding headphones that have disappeared from sight but are still working.
• Bluetooth v5.2. The next update, after 5.1, is Bluetooth 5th generation. The main innovations in this version are a number of security improvements, additional optimization of power consumption in LE mode and a new audio signal format for synchronizing parallel playback on multiple devices.
• Bluetooth v5.3 was introduced at the dawn of 2022. Among the innovations in it, they accelerated the process of negotiating a communication channel between the controller and the device, implemented the function of quickly switching between the operating state in a low duty cycle and a high-speed mode, and improved the throughput and stability of the connection by reducing susceptibility to interference. When unexpected interference occurs in Low Energy mode, the procedure for selecting a communication channel to switch from now on has been accelerated.
• Bluetooth v5.4. introduced at the beginning of 2023, increased the range and speed of data exchange. Also in Bluetooth v 5.4, the energy-saving BLE mode has been improved. This version of the protocol uses new security features to protect data from unauthorized access, has increased connection reliability by selecting the best channel for communication, and prevents connection losses due to interference.

— Radio channel. Wireless connection via radio channel that does not use Bluetooth technology (see above). Such headphones are usually equipped with an adapter that connects to the signal source wired - for example, via USB or mini-Jack 3.5. This connection method is more universal than Bluetooth; it can be used even with devices that do not have wireless modules. In addition, the radio channel provides a long range (often up to several tens of meters), and the sound quality is quite high even without the use of special technologies. The disadvantage of this option is the presence of an adapter, which is not always appropriate: for example, it is more convenient to use Bluetooth headphones with a tablet or smartphone.

- IR channel. Another method of wireless connection, the peculiarity of which is that it does not use radio waves, but infrared radiation. Theoretically, the advantage of such a connection is its resistance to electromagnetic interference, the disadvantage is that it only works in line of sight. In practice, the situation is such that in most cases it is easier to use Bluetooth or a radio channel for a wireless connection. So this option is found exclusively in specialized devices for equipment equipped with their own IR outputs - in particular, among headphones for car monitors.

— USB A. Wired connection to a standard (full-dimensions) USB connector. This option is found exclusively among headphones designed for computers/laptops or gaming consoles. One of its advantages is that sound via USB is transmitted digitally and is processed not by the computer's audio card, but by the built-in headphone converter; such a converter often provides better sound quality than the mentioned audio card. In addition, multi-channel audio can be transmitted via a USB connection - this point will be especially appreciated by gamers. Another advantage is that when using USB headphones, specialized audio outputs remain free, and you can connect other equipment to them - for example, computer speakers or a vibration pad.

- USB C. A relatively new type of USB connector, used in both desktop computers and portable devices - as a successor to microUSB. It is not very different in dimensions, but has a more advanced design - in particular, it is made double-sided, which makes connection easier. Most often complemented by other connection options (they can be either wired or wireless).

- Lightning. A universal connector used in Apple portable devices - iPhone smartphones and iPad tablets - since 2012. Not used by other manufacturers. Accordingly, models with such an interface are designed specifically for Apple technology (primarily iPhone and iPod touch players). This type of connection is especially relevant given the fact that in the latest iPhones the manufacturer has completely abandoned a separate audio output, and the only option for connecting headphones is the Lightning port.

— Branded connector. A connection connector that does not belong to generally accepted standards and is used to a limited extent in equipment from one or several manufacturers. Such connectors are found mainly among headphones for mobile phones. However, due to general standardization, this option has practically disappeared from the scene. Theoretically, the branded connector is also the Lightning described above, but it is separated into a separate category due to the popularity of Apple technology.

The length of the cable supplied with the headphones with the appropriate connectivity.

The optimal cable length depends on the planned format of the "ears". So, for pocket gadgets, 1 metre or less is often enough, for a computer it is already desirable to have a wire for 1 – 2 m, and preferably 2 – 3 m. And models with a longer cable length — 3 – 5 m or even more — are mainly designed for specific tasks, such as connecting to a TV or using in recording studios.

Recall that in some models the cable is removable (see below) and can be replaced if necessary with a longer or shorter one. Also note that there are extension cables that allow you to increase the length of the main wire; such a cable may even be included in the delivery, this point (and the length of the additional cable) is usually specified in the notes.

The audio format supported by the headphones.

— Stereo. Two-channel sound that allows you to create a surround sound effect to a certain extent (due to the difference in the right and left channels). The design of the headphones (two speakers, one for each ear) was originally “sharpened” specifically for stereo, so the vast majority of models support this particular sound format.

— Mono. Single-channel sound that does not create a surround effect. This marking means that this model is equipped with one earpiece ; At the same time, there are two types of such devices on the market. The first is headphones that initially have only one cup and are designed for situations where the second ear needs to be left open (for example, to work on the phone in the office). The second is true wireless devices (see Cable Type), sold singly to replace a lost earphone from the original pair.

— 5.1. Originally, 5.1 was designed to create surround sound that can come from any direction ("surround"). It assumes the presence of 5 main channels (centre, front left / right, rear left / right) and one bass. In headphones, the effect of this sound is achieved through the use of several speakers in each cup. Such models are very convenient when watching movies with multi-channel sound, as well as in games — they provide a powerful immersive effect. On the other hand, such headphones are not cheap, and besides, they require a specifi...c connection method (for example, via USB).

— 5.1 (virtual). Models with support for 5.1 surround sound (see above), in which the surround effect is achieved not due to the number of speakers, but due to special sound processing technologies. This somewhat reduces the accuracy compared to the "non-virtual" multi-channel, but it can significantly reduce the cost and weight of the headphones. However, there can also be several speakers in such models — for example, for separation by frequency.

— 7.1. The 7.1 format is the multi-channel 5.1 described above, supplemented by two more main channels. The localization of these channels depends on the specific variety of 7.1, but anyway they enhance the effect of volume. On the other hand, full support for this format significantly affects the dimensions, weight and price of the headphones, and content with 7.1 sound is produced much less than 5.1.

— 7.1 (virtual). A “virtual” version of the 7.1 format described above, in which the effect of surround sound is provided primarily through special signal processing, and not due to the presence of separate emitters for each channel. Similar to virtual 5.1, this format of operation somewhat reduces the reliability of the sound, but this difference is often imperceptible, and the headphones themselves turn out to be simpler and more inexpensive. Therefore, most modern 7.1 models support the virtual format of this sound.

— 9.1 (virtual). Further development of the idea of multi-channel sound: 5 channels, as in 5.1 (see above), supplemented by 4 more channels for more accurate localization of audible sound. As in other virtual formats, volume in this case is provided by special processing algorithms.

It is worth remembering that the actual sound will depend not only on the headphones, but also on the signal source: for example, a mono recording even in 9.1 “ears” will not become voluminous.

— 3D sound. Surround sound with the localization of sound sources in three-dimensional space allows you to deeply plunge into the atmosphere of films or immerse yourself in a virtual game world. The mechanics of spatial 3D-sound provides localization of sound sources around the listener and in the vertical scan plane. Algorithms for implementing 3D sound in headphones differ in terms of software and hardware support, but all of them are aimed at achieving the effect of realism of what is happening. Surround sound has long been the standard for movies, and in recent years, 3D sound has become increasingly common in games and music tracks.

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 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 coefficient of harmonic distortion produced by this model of headphones.

This parameter determines the amount of non-linear distortion introduced by the headphones into the reproduced sound. The lower it is, the less such distortions, the cleaner and closer to the original sound is. So, an indicator of 1% or more can be considered tolerable at best, from 0.5% to 1% — good, less than 0.5% — excellent (such indicators are acceptable even for monitor headphones), and less than 0.1% — almost perfect.

Note that a low harmonic coefficient in itself does not guarantee high-quality sound — a lot depends on other features of the headphones, primarily the frequency response.