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Evaluation criteria and capabilities of devices / Pult.ru / SurprizingFacts

As it is clear from the title, this post is devoted to a quite trivial thing – the choice of AV receiver. In such publications, quite often "slippery" hints about the advantages of manufacturers or technologies used in the creation of technology are often slipped. Contrary to these rules, I will try to describe the criteria that are meaningful to users as neutrally as possible and describe what is important to consider with such a choice. I would like to describe my personal preferences regarding manufacturers and models of receivers in other articles.

I want to emphasize that I am writing this post for those who are sure that it needs an AV receiver. For those who know that no alternative options in the form of active acoustics or a classical pair of AC + traditional UMZCH do not fit. The advantages of this or that choice can be argued for a long time, but there are situations in which the receiver is a conscious necessity. In the post, we describe several convenient methods for the unparalleled subjective estimation of sound, the principles of calculating the required power, and also the functional capabilities of devices of this type.

5.7.9 or 11?

One of the basic questions that consumers ask when choosing receivers is the number of amplification channels. Often the number of channels determines the cost. Many experts are convinced that using the old good scheme 5.1 is enough to create a realistic surround sound panorama. However, with the advent of Blu-ray discs with new standards, soundtrack recordings to films have changed the situation in recent years. Modern formats allow you to record a seven-channel soundtrack, which in turn determines the trend.

Moreover, the use of advanced surround sound technologies, often involves the use of additional ceiling sources, which in turn require additional channels. For these reasons, seven-channel systems are the most common today. Five-channel receivers are still produced, which are usually present in the initial product lines (the price category is up to 40,000 rubles), and also particularly successful models (or their modernization) that are in high demand despite a small number of channels.

Models with 9 and 11-channel amplification are also widely available on the market, which allow to expand the panorama due to the use of upper front and additional side sources. The use of such systems without sources with 9 or 11 channel audio recording causes a lot of controversy, since additional channels only duplicate those already existing in 5.1 or 7.1 circuit. But it should be noted that such schemes are useful and justified using technologies such as Dolby Atmos and DST-X.

In recent years, receivers with stereo subwoofers (5.2, 7.2, etc. systems) have become popular on the market, .

My personal experience shows that creating a realistic scene is possible with the use of a standard 7.1 circuit without additional front and side speakers, naturally using the appropriate source and Good capabilities of the AU. Such systems will become more relevant with a wide distribution of formats with a large number of channels.

Power and loudness

One of the key acoustic parameters of the AV receiver is power. As in the case of classical UMZCH, when evaluating this criterion, it is necessary to take into account the area of ​​the room, which should be sounded by the device and, accordingly, the power of the acoustic system. In such systems, it is important to have a power reserve, i.e. To make the receiver's power more powerful than the AC.

First, it will minimize the distortion that appears and does not use the limiting volume values. Secondly, if you need to purchase a larger power amplifier, the reserve will be very useful for placing a larger area. It should be noted that the loudness of the system as a whole (ie the level of generated sound pressure) will depend not only on the power of the amplifier and the speaker, but also on the sensitivity of the acoustics. Thus, the same receiver, at the same volume level, can sound differently with different speakers.

When the room size is 30 square meters. Most experts recommend a power gain of at least 50 W (average power per 1 sq. M. Should be about 1.5 W). As I wrote above, these values ​​are rather arbitrary and in many respects depend on the sensitivity of the AU. The presented data are relevant for the AS with a sensitivity of 85-90 dB. Manufacturers often indicate the specific volume (area) of the room their amp capabilities are calculated.

Among other things, it is necessary to take into account the different approaches of manufacturers to the evaluation of the AV receiver's power. A number of Chinese and Asia Minor manufacturers still indicate in PMPO characteristics, i.e. Peak power, which is not any informative indicator. Some crafts of these companies can "possess" a "proud" power of 1000 or 2000 W (PMPO), which can impress an inexperienced buyer, but it will be very far from the truth.

A number of other manufacturers are more sophisticated: they indicate an honest RMS, but the non-linear distortion is measured at low volume levels. At high volume, these distortions increase significantly, and the acoustic system begins to "choke" sound. Therefore, in order to estimate the actual power and sound pressure, it is necessary to conduct preliminary listening of the equipment or buy those devices that you already know.

Distortions and sound quality

Before buying the receiver, you should pay attention to the level of nonlinear distortion. Harmonic distortion (THD) is indicated in the device documentation, as well as in the description of the characteristics on the seller's website (if not indicated, think about the competence of the store and the quality of the device). Intermodulation distortions (IMD) are much less likely to appear in the documentation, and accordingly, when choosing a particular model, it makes sense to look for these characteristics in tests published on the network and check subjectively by ear (as will be discussed below).

For the vast majority of modern receivers The harmonic distortion level is vanishingly small and does not exceed 1% for the entire frequency range at all volume levels. This is due to the fact that most of them are created on the basis of identical amplifying chips according to clearly defined standards. It should also be taken into account that with increasing volume, SOI also grows. The maximum value for intermodulation distortions in modern equipment is considered by most specialists to be 3% (measurement by a standard 2-frequency method).

When purchasing a home device, it is unlikely to be able to use a test bed for Testing. It's not very convenient and troublesome to drive an oscillograph in the showroom. However, there are ways to subjectively assess the sound quality and appearance of nonlinear distortions with a relatively high degree of reliability.
Comparative evaluation of receivers by ear can be carried out similarly to similar tests for acoustic systems. The only difference is that one AS and several different receivers are used.

"A disk with a sinusoidal signal of 315 Hz (0 dB level) is used, the volume is minimized. After starting the "sine" volume gradually increases, until the moment when the sound begins to distort (buzz, etc.). The volume level at which the distortion began is recorded, then the second, third system, etc. is tested. The highest figure indicates a higher quality and faithfulness of reproduction. "

The ideal method of subjective comparison of the quality of AV receivers is the conduct of blind testing with previously known and unfamiliar musical material.

Subjectively define intermodulation distortions when listening to a child or female treble choir. "Blurring" and blurry sound will indicate a high level of IMD. In subjective tests, one should also take into account the fact that the speaker makes much more distortions than the receiver. In addition, ideally use the same acoustics that you plan to use with this receiver (so it's easy to see how the speakers fit into this or that receiver).

Functionality

Integration and interfaces
It is believed that the modern AV receiver should have a wide range of functional capabilities and that they qualitatively distinguish it from traditional amplifying devices.

For modern receivers, a high level of integration with mobile devices is almost mandatory, and Also with the PC through the protocols of wireless data transmission (Bluetooth, AirPlay, Wi-Fi, etc.) and Ethernet, remote control via mobile applications, multi-channel transmission of video and audio information, which makes them compatible with multiroom systems. In addition, many modern receivers are equipped with coaxial and optical audio outputs that allow the audio signal to be transmitted quickly in digital form.

Receivers without support for streaming services are gradually becoming a thing of the past, which by definition involves using Ethernet or a wireless connection to communicate with the network . Given streaming integration, it makes sense to find out whether the receiver can support streaming without loss of quality. It is not uncommon to integrate a player that reads data from an external drive into the receiver. If you need to connect a large number of devices, you should pay attention to the number of HDMI connectors. It is natural that the more of them, the higher the cost of the device.

Acoustic correction
One of the interesting features among modern models on average (from 70 to 100 thousand rubles) price range are systems that can adapt the sound to the features of the room. You can set up automatically, using a special microphone, or manually, by entering data about the speaker system, the location of the speakers and setting the necessary equalization and volume level for each speaker. It should be noted that such possibilities are not available for all AV receivers, moreover, there are cases in which problems of the room can be solved only by using traditional acoustic processing of walls, floor and ceiling.

Video functional
Many users of AV-receivers note the usefulness of the functions of adaptation and deinterlacing of the image. The essence of these functions is the processing of a television, PC or DVD signal by a special graphics processor, in which scaling and artificially increasing the resolution to Full HD or 4K. Experts from the United States especially quote video processors from manufacturers such as Marvell Qdeo or Anchor Bay, who, they said, are adapting the image better than those built into TVs and playback media.

Surround sound
To realize the possibility of surround sound, there are a number of modes and standards that to some extent repeat each other. The most famous brands in this field are Dolby, DTS, Audyssey and THX. The use and selection of these modes can somewhat puzzle the not-too-experienced user, but in certain experiments there are certain advantages.

The most common formats supported by the vast majority of modern AV receivers , Are Dolby Digital (Dolby Digital Plus) and DTS. For high-quality reproduction of Blu-ray discs, Dolby TrueHD, Dolby Atmos, DST-X, DTS-HD Master Audio are used. As for personal impressions, and, according to experts, the most progressive surround sound technologies today are Dolby Atmos and DST-X, which allow you to get the most realistic sound "canvas" with an extremely detailed, deep and precise scene. At the same time, for full-fledged operation of these technologies, ceiling acoustics are required, and, accordingly, the use of the 7.1 receiver.

Another functional feature, realized in many AV-receivers, is the decoders, which allow to convert the stereo signal into surround 5.1 or 7.1 sound. These include Dolby Pro Logic IIx, more advanced Dolby Pro Logic IIz, Audyssey DSX, and DTS Neo: 6. I appreciate the effect of using such modes as impressive and interesting. But as a person who often prefers traditional stereo and quickly gets tired of listening to this (especially music).

Normalization of loudness and compression
I've never used the compression function as needed – only as an experiment, but for many it really is needed. It is useful for those who watch TV channels with aggressive advertising, which often has a higher overall volume level. It will be superfluous for those whose neighbors have auditory hyperesthesia and react very painfully to an increase in volume beyond the wall. The digital compressor cuts the amplitude and frequency peaks, which allows quite comfortable and without detriment to the neighbors watching the movie at night.

The result

The criteria for choosing an AV receiver are clearly determined by three factors:

  • the need for certain functional capabilities;
  • sound and image quality;
  • user's budget.

With the increase in the number of interfaces, decoders, operating modes, integration capabilities and other user functions, the cost of the device naturally increases. The majority of our shoppers (70% of those who answered this question) believe that a good AV receiver with sufficient functionality and capabilities can be purchased in the price range from 40 to 90 thousand rubles. Personally for me the most interesting options were receivers using technologies Dolby Atmos and DST: X, equipped with the ability to manage via mobile applications. It is these features that I consider to be the most important, after the basic criteria of sound quality.