Frequency range
The range of audio frequencies that the audio receiver can handle. The wider this range, the more complete the overall picture of the sound, the less likely it is that too high or low frequencies will be “cut off” by the output amplifier. However, note that the range of sound audible to a person is on average from 16 Hz to 20 kHz; There are some deviations from this norm, but they are small. At the same time, modern Hi-Fi and Hi-End technology can have a much wider range — most often it is a kind of "side effect" of high-end circuits. Some manufacturers may use this property for promotional purposes, but it does not carry practical value in itself.
Note that even within the audible range it does not always make sense to chase the maximum coverage. It is worth, for example, to take into account that the actually audible sound cannot be better than the speakers are capable of giving out; therefore, for a speaker system with a lower threshold of, say, 70 Hz, there is no need to specifically look for a receiver with this figure of 16 Hz. Also, do not forget that a wide frequency range in itself does not absolutely guarantee high sound quality — it is associated with a huge number of other factors.
Permissible speaker impedance (Ω)
The lowest speaker impedance that the audio receiver can handle normally.
The nominal impedance of the speakers, also referred to as the term "impedance", is one of the key parameters in the selection of audio system components: for normal operation, it is necessary that the speaker impedance match the characteristics of the amplifier. If the speaker impedance is greater, the sound volume will decrease significantly, if it is less, distortion will appear in it, and in the worst case, even overloads and breakdowns are possible. Therefore, in the characteristics of receivers, it is usually the minimum resistance that is indicated — after all, connecting a load of too low impedance is fraught with more serious consequences than too high.
