Tuner bands
Radio ranges received by the tuner of the music center. Today, the most common ranges supported are:
— FM. Part of the ultra-short-wave (VHF) range from 87.5 MHz to 108 MHz. Uses frequency modulation, which allows you to broadcast music in stereo with fairly high sound quality, as well as transmit RDS signals (see RDS). At the moment, most music radio stations in the CIS broadcast in this range, as a result of which FM is supported in the vast majority of audio systems. The disadvantage of this option is the limited reception area - a maximum of several dozen kilometers from the transmitter - so FM broadcasts can usually be listened to within one city and its surrounding areas.
— AM (from English amplitude modulation) — radio broadcasting using amplitude modulation. Usually, this term refers to broadcasting on medium waves in the range of 520–1610 kHz; most consumer AM receivers are designed for these same frequencies. The range of AM stations can be hundreds of kilometers, but the sound quality is lower than on FM, so this format is mainly used for talk and news radio stations.
— DAB+. DAB is an abbreviation for Digital Audio Broadcasting, i.e. “digital radio broadcasting”; and “+” means an improved version of this standard. Formally, DAB+ is not only a range, but also a signal transmission format: unlike all the options described above, it is, as the name suggests, digital. This provides a number of advantages over traditional transmitter...s — in particular, a greater range at lower power and high quality of the transmitted sound. In addition, this sound is practically not subject to distortion: weak interference does not affect its quality, and with a critical decrease in transmitter power, the signal is not distorted, but disappears completely. The latter, however, can be written down as a disadvantage; but the only truly significant disadvantage of this option is its low prevalence (so far) in the CIS countries. Technically, such broadcasting can be carried out in any range above 30 MHz, but in practice, several options are used (depending on the country), related to the VHF range. Please note that DAB+ tuners are capable of receiving original DAB radio broadcasts, but not vice versa.
Radio Data System (RDS)
Tuner support for Radio Data System technology. This technology is used mainly in the FM band; it allows, in addition to the sound signal, to transmit additional textual information by radio — for example, the names of broadcast compositions, announcements, advertising messages, etc. For RDS-enabled audio systems, this information is shown on the display.
Power per channel
Nominal sound power (see "System power") on each of the main channels of the audio system. This indicator is most often indicated in models with a subwoofer (see "Number of channels"); knowing it, you can estimate the power distribution between the main speakers and the subwoofer.
Frequency range
The total frequency range reproduced by the acoustics of an audio system. Measured from the lower threshold of the lowest frequency speaker to the upper threshold of the highest frequency: for example, in a 2.1 system with main speakers at 100 – 22000 Hz and a subwoofer at 20 – 150 Hz, the total value will be 20 – 22000 Hz.
In general, the wider the frequency range, the fuller the reproduced sound will be, the less low and high frequencies will be lost due to insufficient acoustic capabilities. On the other hand, do not forget that the actual sound quality also depends on a number of other parameters — primarily the frequency response. In addition, human audible frequencies range from 16 Hz to 22 kHz; deviations from these values are very small, and the upper limit also decreases with age. Therefore, from a practical point of view, it does not make sense to provide too large a frequency range; and impressive performances like 10 – 50000 Hz, found in top-class models, are usually more of a kind of "side effect" of high-quality speakers (and at the same time — a marketing ploy) than a really significant moment.
Phase inverter
The phase inverter is a tube installed in the column housing and having an outlet to the surrounding space. The length of the tube is chosen so that a signal comes out of the outlet, inverted in phase relative to the signal from the front of the diffuser. This enhances the sound pressure and improves the sound of the speakers, including at low frequencies. Note that such audio systems should be placed at a certain distance from walls, furniture, etc. — otherwise, a hum may occur due to the movement of air through the phase inverter tube.
A similar function in some models is performed by a passive radiator (see below).
Passive emitter
A passive radiator can be simply described as a low-frequency speaker that does not have its own reproducing system (coil with magnet). It is driven by pressure fluctuations created by active drivers and acts as a resonator to deliver deep, rich bass—especially useful for systems that do not include a subwoofer. At the same time, unlike phase inverters, passive radiators do not generate additional noise.
