Analysis of basic theoretical knowledge of professional audio

Author: 　 From: 　 DateTime: 2022-06-15　 Hits: 4641　 【Font: T  T 】

Introduction to terms of sound technology knowledge
Learning always starts with theory, and understanding audio equipment is no exception. Being familiar with professional audio knowledge and professional terms is the first step to play with audio equipment. Only by laying a good foundation can we better move forward. The colorful and complex sound terms make many people "head big". Due to the limitation of space, the editor will briefly introduce the more common terms to you, so as to facilitate you to get started quickly.
Output power: it indicates the output power of the power amplifier under a certain load. Generally, the output power under 8 ohm load, 4 ohm load or 2 ohm load is indicated in the power amplifier manual. At the same time, it also indicates the output power under 8 ohm load or 4 ohm load under bridge state. This output power represents the rated output power of the power amplifier, not the maximum or peak output power.
Load impedance: it indicates the load capacity of the power amplifier. The smaller the load impedance, the stronger the current capacity that the power amplifier can pass through. Generally speaking, the minimum load impedance of most power amplifiers is 4 ohms, and the minimum load of power amplifiers with good quality is generally 2 ohms. It can load 4 ohm power amplifier in dual channel, and the minimum load is 8 ohm in bridge state. It can load 2 ohm power amplifier in dual channel, and 4 ohm in bridge state. In the bridge state, only 8 ohm power amplifier can be loaded, and lower impedance can not be loaded, otherwise the power amplifier will be burned due to excessive current.
Frequency range: indicates the working frequency band that the power amplifier can amplify, generally 20-20000 Hz. Generally, there is a suffix after this data, such as - 1 / + 1dB, which represents the error or floating range of this frequency range. This value is about small, indicating that the frequency response curve within the frequency range is more straight. If the frequency response range of the power amplifier is tested at - 3 dB, the sound of the power amplifier may not be so straight.
Damping factor: This is the ratio of the internal resistance of the power amplifier to the load impedance. The damping factor = the impedance of the speaker ÷ (the internal resistance of the power amplifier + the impedance of the speaker line). The control ability of the power amplifier with high damping coefficient to the speaker unit is strengthened, which can make the response of the unit closer to the requirements of the output signal of the power amplifier, but too high damping coefficient will lead to poor low-frequency ductility of the speaker, The sound is dry and hard. A relatively low damping coefficient can obtain a soft bass, but a low damping coefficient will cause the bass to become sluggish and unclean. The damping coefficient of general power amplifier is 200 - [email]= 1000@8 ] 1000@8 [/ email] ohms. Poor line quality and high line resistance of the speaker will also affect the damping coefficient of the power amplifier, resulting in the weakening of the control force of the power amplifier on the speaker and the dispersion of sound.
Input sensitivity: This is a voltage concept, which indicates the size of the signal voltage at the input when the power amplifier reaches full power output. Generally, the input sensitivity voltage of the power amplifier is between 0.775v (0dB) and 1.5V (+ 6dB). The higher the sensitivity voltage, the lower the input sensitivity. Some high-quality amplifiers have low input sensitivity because of the deeper negative feedback circuit, so they have lower distortion, wider frequency response and better sound quality.
S / norsnror human noise: refers to the ratio of the signal voltage of the power amplifier to the background noise voltage. The larger this value is, the lower the noise of the power amplifier is. The signal-to-noise ratio of general professional products is about 100 dB. When marked with a positive value, the higher the better (some power amplifiers use a negative value, and the smaller the value, the better). Attenuating the input level gain of the power amplifier (turning down the volume knob of the power amplifier) will reduce the signal-to-noise ratio of the power amplifier.
2、 Basic skills of purchasing audio equipment
Playing music with knowledge and no equipment is like "talking on paper". Therefore, it is very important to choose a good set of sound equipment, but now the sound box brands in the sound market are mixed. How to find a suitable sound equipment with reasonable price in the complex market makes many people at a loss. The following editor will teach you some skills to identify the quality of audio equipment.
（1） Natural tonal balance
First of all, the sound reproduction of the speaker should be true. The re released human voice and instrumental sound should be as close to the original sound as possible without distortion. The sound heard should be smooth and silent, without the strongest and weakest sound. The intermediate frequency band and treble should not be too loud or hold. You can find recordings of instrumental music (such as piano music) with a wide frequency range to play. Pay attention to the change of timbre in low, middle and high scales.
（2） Sound characteristics
Although the overall sound reproduction characteristics of speakers are very important, good speakers should also perform well in the following special occasions:
Frequency balance: you can listen to different frequency bands in turn. The bass should be compact, clear, accurate in tone, without buzzing, sludging or blurring; As the main part of music, the midrange segment is more important. The human voice and instrumental sound should be natural and detailed, and should not be too loud or stuffy, too bright or too light. The treble should be open, air and extensible, without screaming or fading.
Analytical power: listen carefully to see if you can hear details in music, such as the decline of cymbals or pianos, hall sounds in concert halls or jazz clubs. If you can't hear the details of low level clearly, it means that the speaker lacks transparency. In order to achieve a real and satisfactory playback effect, the resolution at low level is very important. This is also the difference between a good speaker and a bad speaker.
Transient response: the speaker shall be able to reproduce the transient in music. The sound when you just hit the string drum or dial the guitar should be strong and accurate, and should not make people "surprised", "excited" or "slow" and "dull". In addition, naturally fading sounds, such as cymbals and the "tail" of voice, should gradually fade and stop suddenly.
（3） Sound environment of speaker
If you try to listen to the speaker in a sound store with improper placement, you are unlikely to hear all the performance of the speaker. Because the placement of the speaker in the room is very important, even if you move the speaker forward or backward a few centimeters, it will greatly change the low-frequency response of the speaker. When the speaker is placed in a room that can enhance or weaken the bass, the tonal balance will change, or you will hear rich bass or no bass. Moreover, when the speaker is not placed properly, the sound and sound of the original audio-visual positioning are not reached. Therefore, we should find a proper place for the speaker at home, so that the speaker can fully exert its power and show its skill
（4） Listen to familiar music
Because the recording quality of CD records is very far related, there have been many times, so when you go to the audio store to audition and buy speakers, you'd better bring more excellent CD records that you usually listen to well. In this way, you can hear what is originally on the CD recording and what is held by the speaker.
3、 Avoid mistakes in audio use
It is important to have a set of high-grade equipment, but it is also important to use them correctly. At present, among ordinary audio lovers, there are some misunderstandings in use that should be avoided.
（1） Put the equipment in the cabinet. Some people put the equipment into the customized cabinet for decoration and protection, which will make the sound turbid due to the latent vibration caused by the space in the cabinet. Due to insufficient circulating air, the power amplifier and other equipment are easy to overheat and age. If the speaker is installed into the wall, the sound effect will become stiff.
（2） Stacking equipment. Many people like to place DVD players, amplifiers, tuners, digital to analog converters and other machines on top of each other, which will cause mutual interference, especially the serious interference between radium camera and power amplifier, which will make the sound color hard and produce a sense of depression. The correct way is to put the equipment on the sound stand designed by the manufacturer.
（3） The power plug is positive or negative. A good system of positive and negative processing of power plug, with clear sound color and natural and smooth; If the positive and negative are inconsistent or uneven, the timbre will be hard and rough.
（4） Loose and unclean wiring. If the sound of the system is dry and hard, one of the reasons may be poor contact, such as loose plug, oxidation of contact surface, dust or oil stain, so it should be checked frequently to keep the contact surface clean.
（5） Speakers are placed "according to local conditions". Some people put the speakers in a position to accommodate the furniture because there were other furniture in the room first. If it is correct, first determine the listening distance, and then place the speaker at 1 / 3 between the seat and the opposite wall. The spacing of the speaker is 0.7 times the direct distance between the listener and the speaker, and the height should be flush with the listener's ear and the tweeter.
（6） Improper wiring handling. When processing wiring, do not tie the power line and signal line together, because AC will affect the signal; The signal wire or horn wire shall not be knotted, otherwise the sound color will be affected; If the signal line or horn line is too long, it can be shortened. Many signal lines are directional. Don't make a mistake.
（7） Take it for granted to deal with the sound effects of the room. In addition to clear sound and sound insulation, what is more important is the treatment of sound wave reflection and refraction, which needs to consider the volume, size, firmness and application of materials of the room. If you are not an expert, even if you decorate the room luxurious and beautiful, the sound is difficult to achieve the best effect.
（8） Deceive yourself and others. For example, the effect of playing one kind of concert with equipment is very good, while playing another kind of music is not ideal, which shows that the system has not reached the ideal level and needs to learn more, listen more and observe more, so as to improve it.