Comparison Denon AVR-X250BT vs Denon AVR-X520BT

In this case, the function of automatic adjustment of each individual sound channel in terms of level and delay is implied so that all of them together provide surround sound that best matches the intention of the creators of the film or musical composition. The need for such a setting is due to the fact that practically no room (neither residential, nor even specialized) is acoustically perfect: the sound propagation is affected by the wall material, floor covering, furniture (sofas, wardrobes, etc.) and other factors. Therefore, the technically correct arrangement of the speakers alone does not guarantee a full-fledged surround sound.

Typically, automatic tuning uses a microphone placed at the intended listening position. During the calibration process, the device outputs test sound signals through the acoustics and “listens” to the features of the sound through the microphone, if necessary, independently changing the audio parameters.

Such a function can greatly simplify the preparation for work — after all, the device will carry out the main part of the setup on its own. However, keep in mind that even in the most advanced receiver models, automatic calibration algorithms are not perfect. As a result, it is highly likely that the automatically set parameters will not meet the tastes of demanding audiophiles. In addition, the reliability of the calibration is also highly dependent on the characteristics of the microphone used — and options with high...sound quality can be quite expensive.

The maximum number of channels that the receiver can output to external speakers. This parameter is specified for all types (see above): even AV processors that do not have an amplifier as such are often equipped with a very extensive set of audio processing tools (and this set is sometimes even wider than in models with amplifiers).

The most popular options by the number of channels today are as follows:

— 2.1. The simplest option found in modern AV receivers is the classic two-channel stereo sound, supplemented by a third channel for a subwoofer. It is worth noting here that the "volume" of such a sound is very limited: it allows you to simulate the shift of the sound source to the left or right, but does not cover the space on the sides and behind the listener. Receivers of this kind are usually entry-level devices.

— 3.1. Such a system is usually the 2.1 described above, supplemented by a third front speaker — in the centre. This provides a more authentic sound from the front. And for some 3.1 systems, design tricks are claimed that allow them to be used for surround sound, similar to 5.1. Rear channels in such systems are simulated by reflecting sound from the walls behind the user. Of course, the sound accuracy is noticeably lower than that of a full-fledged 5.1, but this option may be optimal in tight spaces where there is no space for a full set of six-channel acoustics.

— 5.1. The most popular surround sound format that can provide the effect of "environment". 5 main channels include a centre, two front (left-right) and two rear (similarly), a unit indicates a separate low-frequency channel for a subwoofer.

— 5.2. Sound format similar to 5.1 above, except for two channels for subwoofers instead of one. This improves the quality of the bass sound, which can be useful for films with a lot of special effects, live performance recordings, etc.

— 6.1. A sound format with an expanded number of main channels relative to the classic 5.1. The sixth main channel in this format is usually the centre back — this increases the accuracy of the sound transmission in the back of the stage.

— 6.2. 6.1 version of the format described above, supplemented by a second subwoofer; this improves the quality of low frequency transmission and allows you to cover a larger area.

— 7.1. With this sound format, five main channels (similar to the 5.1 system described above) are supplemented with two more. There are a lot of options for installing speakers for these channels — for example, these can be additional speakers above two front or two rear speakers, two separate side speakers, an additional “centre” pair on the rear channel, etc. Anyway, an increase in the number of channels makes it possible to achieve a more accurate transmission of “surround” sound compared to 5.1, however, much less content has been released for such systems.

— 7.2. A variation on the 7.1 format (see above) that allows the use of two separate subwoofers; this increases the accuracy of the transmission of low frequencies and expands the possibilities for their adjustment.

— 8.4. A specific variant found in single models of AV receivers. It is not so much a generally accepted sound format as an illustration of advanced configuration options: up to 8 main speakers and up to 4 subwoofers can be connected to the device, which gives very extensive fine-tuning options (however, such options are not cheap).

— 9.1. One of the most advanced surround sound formats today: it includes 5 classic main channels (similar to a 5.1 system) and 4 additional ones, the location of which can be different — for example, two side speakers and two upper ones above the left and right front, or even 4 speakers, directed towards the ceiling. The 9.1 format allows you to achieve very high fidelity of multi-channel audio transmission, but it is expensive, difficult to set up, and very little content has been released for such systems.

— 9.2. Modification of the above 9.1 format, supplemented by a second subwoofer for more accurate and high-quality reproduction of low-frequency sound.

— 11.1. Further, after 9.1, expansion and improvement of the idea of multi-channel sound. Usually in 11.1 systems, the five "classic" main channels (see 5.1) are supplemented with six more in the following way: two speakers to the left and right of the centre (in addition to the left and right front), two height speakers above the main front and two more — above main rear. This significantly increases the accuracy of surround sound transmission and adds the ability to shift it not only horizontally, but also vertically. However, the price and complexity of setting up such systems is appropriate, so they are designed more for the professional sphere (for example, cinema halls of entertainment centers) than for home use.

— 11.2. Systems almost identical to those described above 11.1, but supplemented by a second subwoofer. The latter is useful not only for reliability, but also for covering a vast area.

— 12.4. A top-of-the-line AV receiver option that is designed to handle all existing surround sound formats (including "true" 3D sound) and offers extremely wide customization options (albeit at an appropriate price).

— 13.2. Another format typical for luxury AV receivers and similar to 12.4 described above (with the exception of differences in the number of channels, which are not critical in this case).

— 15.1. A very rare and expensive option, designed for the use of mainly advanced acoustic systems — in particular, the halls of small cinemas.

Note that this paragraph indicates the most advanced sound format that the receiver is capable of working with; the general set also includes simpler options. For example, 7.1 systems usually handle 5.1 without any problems, not to mention stereo.

— AM/FM radio. The presence of a built-in tuner that allows you to receive AM and FM radio broadcasts without additional devices (except perhaps an antenna is required, and then not always). In FM, it is possible to realize the transmission of high-quality stereo sound, however, the waves propagate only within the line of sight (10-20 km); therefore, most of the stations in this range are classified as "urban music". In AM, the transmission range is already measured in hundreds of kilometers, but the sound quality is noticeably lower; therefore, such stations usually specialize in talk programs (particularly news).

— USB stick. The ability to connect a USB drive to the receiver — for example, a "flash drive" or an external hard drive — and play content from it directly. This requires a USB connector. Most often, in models with this function, it is located on the front panel (see below) — this provides ease of connection; at the same time, there are exceptions. Also note that the very presence of USB does not necessarily imply the possibility of playing from external media — this interface can be used for service purposes, for example, to update the firmware or play from a PC (see "Advanced (inputs) — USB Type B").

— Network audio streaming. The ability to play streaming audio over a local network or the Internet (including from services like Grooveshark o...r Last.Fm). The name "streaming" is due to the fact that each song is played directly from the network, without being written to the receiver's own permanent storage. This function, by definition, requires connection to computer networks; most often, a Wi-Fi module is used for this purpose (see "Interfaces") or a LAN connector.

— Internet radio. The ability to use the receiver to receive and play Internet radio broadcasts. This feature is similar in many ways to the network audio described above — in particular, it requires a network connection to work, and the data is streamed; however, in the case of network audio, the user himself chooses what and when to listen, here the broadcast is similar to conventional radio transmissions and is controlled from the radio station. Actually, many major stations broadcast their programs not only on the traditional air, but also via the Internet; There are also specialized projects broadcasting only on the Web. In general, the choice of programs is much more extensive than for conventional radio broadcasting — after all, Internet radio has no range restrictions. And the receivers themselves may provide additional tools for managing such broadcasting — for example, catalogs, search by genres, languages, etc.

Audio and video file formats that the receiver is capable of playing on its own. Models with player features generally support most popular media file types (particularly AVI, MPEG and MKV for video, MP3, WAV and WMA for audio), but the file set may have its own peculiarities. This item allows you to find out.

HDMI interface version supported by the receiver. Usually, all HDMI connectors available in the device correspond to this version — both inputs (see above) and outputs (see below). Here are the current options:

— v 1.4. The oldest of the current versions, released in 2009. However, it supports 3D video capable of working with resolutions up to 4096x2160 at 24 fps, and in Full HD resolution, the frame rate can reach 120 fps. In addition to the original v.1.4, there are also improved modifications — v.1.4a and v.1.4b; they are similar in terms of basic features, in both cases the improvements affected mainly work with 3D content.

-v 2.0. Significant update to HDMI introduced in 2013. In this version, the maximum frame rate in 4K has increased to 60 fps, and the audio bandwidth has increased to 32 channels and 4 separate streams simultaneously. Also from the innovations, we can mention support for the ultra-wide format 21:9. In the v.2.0a update, HDR support was added to the interface capabilities, in v.2.0b this feature was improved and expanded.

— v 2.1. Despite the similarity in name to v.2.0, this version, released in 2017, was a very large-scale update. In particular, it added support for 8K and even 10K at speeds up to 120 fps, as well as further expanded the possibilities for working with HDR. Under this version, its own cable was released — HDMI Ultra High Speed, all v.2.1 features are available only when using cables of this standard,...although basic functions can be used with simpler cords.

The presence of a USB port on the front panel of the receiver. The USB interface can be used both for connecting external media and direct content playback (see "Tuner and playback"), and for connecting the receiver itself to a computer as a peripheral device (see "USB Type B"). However, the first type of USB connector is usually placed on the front panel; this is very convenient for those who plan to often listen to music and watch videos from flash drives and other similar media.

HDMI input on the front panel of the receiver. This arrangement is much more convenient for connection than placement on the side or rear panel. For details on the interface itself, see the first of the "HDMI" items above.

The maximum power consumed by the receiver during normal operation. The power consumption of the device depends on this parameter, so if saving energy is crucial for you, you should pay attention to it. Also, information on power consumption is useful if you have doubts about the claimed characteristics of the built-in amplifier: if the total power of all channels is greater than the total power consumption of the receiver, then there is an error somewhere in the numbers.

Ability to control the AV receiver from a portable device. Note that this can be not only a smartphone, but also any other gadget that is compatible with a special control application — for example, a tablet. Connection with such a "remote control" is carried out via the wireless standard Wi-Fi or Bluetooth (see "Interfaces"). This allows you to control the device even through walls, while classic remote controls use the infrared channel and work only in the line of sight. In addition, the functionality of the control application can be almost unlimited, and the manufacturer can also update it by adding new features.