Select AV receiver: evaluation criteria and device capabilities

Published on July 24, 2017

Select AV receiver: evaluation criteria and device capabilities

    As the name implies, this post is devoted to quite a trivial thing - the choice of the AV-receiver. In such publications, the “denim” hints on the advantages of the manufacturers or the technologies used to create the equipment often slip quite often. Contrary to similar rules, I will try to be as neutral as possible to describe the criteria that are meaningful to users and tell you what is important to consider when making such a choice. My personal preferences regarding manufacturers and models of receivers, I will describe 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 classic pair of speakers + traditional UMZCH will not do. One can argue about the advantages of this or that choice, but there are situations in which the receiver is a conscious need. The post describes several convenient methods of non-instrumental, subjective sound assessment, principles for calculating the required power, as well as the functionality 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 good old 5.1 scheme is enough to form a realistic surround sound panorama. However, with the advent of Blue-ray discs with new standards for recording film soundtracks, the situation has changed somewhat 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 technology does not rarely involve the use of additional ceiling sources, which, in turn, require additional channels. For these reasons, the most common today are exactly seven-channel systems. Five-channel receivers are still being produced, which, as a rule, are present in the initial rulers (price category up to 40,000 rubles), and especially successful models have been preserved (or their upgrades) that are in high demand despite a small number of channels.

    Models with 9 and 11-channel amplification are also widely represented on the market, which make it possible to expand the panorama through the use of upper frontal and additional side sources. The use of such systems without sources with 9 or 11 channel sound recording causes a lot of controversy, since the additional channels only duplicate the existing ones in the 5.1 or 7.1 scheme. But it should be noted that such schemes are useful and justified when 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. It is believed that the stereo in the low-frequency region is capable of enhancing the effects of surround sound.

    My personal experience shows that creating a realistic scene is possible when using the standard 7.1 scheme without additional front and side speakers, of course with the appropriate source and good speaker features. However, with widespread formats with a large number of channels, such systems will become more relevant.

    Power and volume


    One of the key acoustic parameters of the AV receiver is power. As in the case of classical UMZCH, when evaluating this criterion, one should take into account the area of ​​the room, which should be announced by the device and, accordingly, the power of the acoustic system. In such systems, it is important to have a power reserve, i.e. make so that the receiver power was more speaker power.

    Firstly, it will allow minimizing the distortion that occurs and not use the limit values ​​of the volume. Secondly, if there is a need to purchase more power plants, the reserve will be most welcome for a larger area. It should be noted that the volume of the system as a whole (i.e. the level of sound pressure generated) will depend not only on the power of the amplifier and speakers, but also on the sensitivity of the acoustics. Thus, the same receiver, at the same volume level, may sound differently with different speakers.

    With a room size of 30 square meters. m. most experts recommend a gain power of at least 50 W (respectively, the average power per 1 sq. m. should be about 1.5 W). As I wrote above, these values ​​are fairly arbitrary and largely depend on the sensitivity of the speakers. The data presented are relevant to speakers with a sensitivity of 85-90 dB. Manufacturers often indicate what kind of volume (area) of the room their reinforcing capabilities are designed for.

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

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

    Distortion and sound quality


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

    For the vast majority of modern receivers, the level of harmonic distortion 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 based on identical amplifying chips according to clearly defined standards. It should also be borne in mind that with increasing volume, SOIs also grow. The limit value for intermodulation distortions in modern equipment is considered by most experts to be 3% (measurement by the standard 2-frequency method).



    When buying a home device is unlikely to be able to use the test bench for testing. To drive an oscillograph into the showroom is not very convenient and rather troublesome. However, there are ways to subjectively assess the sound quality and the appearance of nonlinear distortion with a relatively high degree of confidence.
    A comparative assessment of receivers by ear can be carried out similarly to similar tests for acoustic systems. With the only difference that one speaker is used and several different receivers.
    “They use a disk with a sinusoidal signal of 315 Hz (level 0 dB), the volume is turned to the minimum. After starting the “sinus” the volume gradually increases until the sound starts to distort (hum, etc.). The volume level at which the distortion began is recorded, then the second, third system, etc. are tested. The highest rate indicates higher quality and fidelity. ”

    An ideal way to subjectively compare the quality of AV receivers is to conduct blind testing with previously known and unfamiliar musical material.

    Subjectively determine the intermodulation distortion can be when listening to children's or female trekking choir. “Contamination” and fuzziness will indicate a high level of IMD. In subjective tests should also take into account the fact that the AU introduces significantly more distortion than the receiver. In addition, ideally, use exactly the acoustics that you plan to use with this receiver (thus, it is easy to understand how much the speakers fit into one or another receiver).

    Functionality


    Integration and Interfaces
    It is believed that a modern AV-receiver should have wide functionality and that they qualitatively distinguish it from traditional amplifying devices.



    For modern receivers, a high level of integration with mobile devices, as well as with a PC via wireless data transfer protocols (Bluetooth, AirPlay, Wi-Fi, etc.) and EtherNet, remote control via mobile applications, multi-channel video and audio information is almost mandatory. that makes them related to multiroom systems. In addition, many modern receivers are equipped with coaxial and optical audio outputs that allow you to quickly transmit an audio signal in digital form.

    Receivers without the support of streaming services are gradually becoming a thing of the past, which, by definition, involves using EtherNet or a wireless connection to communicate with a network. Given the streaming integration, it makes sense to find out whether the receiver can support streaming without loss of quality. There are often cases of integration into the receiver of a player reading data from an external drive. If you need to connect a large number of devices should pay attention to the number of HDMI connectors. In this case, it is logical 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) in the price range are systems that can adapt the sound to the characteristics of the room. You can adjust automatically, using a special microphone, or manually, entering information 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 not all AV-receivers have such opportunities, moreover, there are cases in which the problems of a room can be solved only by using traditional acoustic treatment of walls, floor and ceiling.

    Video functionality
    Many users of AV-receiversnote the usefulness of image adaptation and deinterlacing functions. The essence of these functions is the processing of a television, PC or DVD signal with a special graphics processor, at which scaling occurs and an artificial increase in resolution up 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 say, adapt the image better than the built-in TVs and playback tools.

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



    The most common formats that support the vast majority of modern AV receivers are Dolby Digital (Dolby Digital Plus) and DTS. Dolby TrueHD, Dolby Atmos, DST-X, DTS-HD Master Audio are used to fully play Blu-ray discs. As for personal impressions, and, according to experts, the most advanced 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 accurate scene. At the same time for the full operation of these technologies, ceiling acoustics are needed, and accordingly, the use of a 7.1 receiver.


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

    Normalization of volume and compression
    I have never been able to use the compression function as needed - only as an experiment, but for many it is really needed. Useful for those who watch TV channels with aggressive advertising, in which the overall volume level is often higher. This function will also be useful for those whose neighbors have audible hyperesthesia and are very sensitive to loudness behind the wall. The digital compressor cuts the amplitude and frequency peaks, which allows you to watch the movie at night quite comfortably and without damage to your neighbors.

    Total


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

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

    As the number of interfaces, decoders, operating modes, integration capabilities, and other user functionality grows, the cost of the device naturally increases. Most buyers of our store (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. For me personally, the most interesting options are receivers using Dolby Atmos and DST: X technologies, equipped with the ability to control via mobile applications. It is these features that I consider the most important, after the basic criteria of sound quality.