The performance of the overall technical indicators of the audio system depends on the performance of each unit. If the technical indicators of each unit in the system are high, then the overall technical indicators of the system are good. There are six main technical indicators: frequency response, signal-to-noise ratio, dynamic range, distortion, transient response, stereo separation, and stereo balance.
1. Frequency response: The so-called frequency response refers to the frequency range when the audio equipment is replayed, and the relationship between the amplitude of the sound wave and the frequency. Generally, the frequency range of 1000 Hz is used as a reference to detect this indicator, and the logarithm is used to express the frequency range in decibels (dB).
The overall frequency response of the audio system is theoretically required to be 20-20000Hz. In actual use, it is often unable to meet this requirement due to circuit structure, component quality, etc., but generally at least 32-18000Hz.
2. Signal-to-noise ratio: The so-called signal-to-noise ratio refers to the ratio of the playback sound of the audio system to the sound source software and the new noise generated by the entire system. The noise mainly includes thermal noise, AC noise, mechanical noise and so on. Generally, this indicator is expressed in decibels (dB) as the logarithmic ratio of the rated output power of the playback signal to the system noise output power when there is no signal input.
Generally, the signal-to-noise ratio of the audio system needs to be above 85dB.
3. Dynamic range: Dynamic range refers to the logarithmic value of the ratio between the maximum undistorted output power of the audio system during playback and the system noise output power at static state, expressed in decibels (dB). Generally, the dynamic range of a sound system with better performance is above 100 (dB).
4. Distortion: Distortion means that after the audio system replays the audio source signal, compared with the original signal, some parts of the original audio source signal (waveform, frequency, etc.) have changed.
The distortion of the sound system mainly has the following types:
1) Harmonic distortion: The so-called harmonic distortion means that the sound reproduced by the audio system has many additional harmonic components than the original signal source. The additional harmonic component signal is the frequency multiplication or frequency division of the signal source frequency , which is caused by the negative feedback network or amplifier nonlinearity. The harmonic distortion of the hi-fi system should be less than 1%.
2) Intermodulation distortion: Intermodulation distortion is also a kind of nonlinear distortion. It is a mixture of two or more frequency components in a certain proportion, and each frequency signal is modulated with each other. After passing through the playback device, a newly added nonlinear signal is generated. The signal includes sum and difference signals between the respective signals.
3) Transient distortion: Transient distortion is also called transient response. It is mainly caused by the slow reflection of the amplifier when a large transient signal is suddenly added to the amplifier, which causes the signal to be distorted. Generally, after the input square wave signal passes through the playback device, observe whether the envelope waveform of the output signal of the amplifier is similar to the input square wave waveform to express the ability of the amplifier to follow the transient signal.
5. Stereo separation: Stereo separation indicates the isolation between the left and right channels in a stereo system, and it actually reflects the degree of crosstalk between the left and right channels. If there is a lot of crosstalk between the two channels, the three-dimensionality of the reproduced sound will be reduced.
6. Stereo balance: The stereo balance indicates the gain difference between the left and right channels in the stereo playback system. If the imbalance is too large, the sound image positioning of the replayed stereo will shift. Generally, the stereo balance of a high-quality audio system should be less than 1dB.