Analysis of basic theoretical knowledge of professional audio

Brief introduction of sound technology knowledge terms

Learning has always started with theory first, and understanding audio equipment is no exception. Familiarizing professional audio knowledge and terminology is the first step in playing audio equipment. Only by laying a solid foundation can you move forward. The colorful and complicated audio terminology makes many people "head big". Due to space limitations, the editor will briefly introduce you to the more common and commonly used terminology to facilitate your quick start.

Output power: Indicate the output power of the power amplifier under a certain load. Generally, the output power in the state of 8 ohm load, 4 ohm load or 2 ohm load is indicated on the power amplifier manual, and it will also indicate that the power is placed in the bridge state. The output power at 8 ohm load or 4 ohm load. This output power represents the rated output power of the power amplifier, not the maximum or peak output power.

Load impedance: Indicates the load capacity of the power amplifier. The smaller the load impedance, the stronger the current capacity that the power amplifier can pass. Generally speaking, the minimum load impedance of most power amplifiers is 4 ohms, and the minimum load of good quality power amplifiers is generally 2 ohm. It can load a 4 ohm power amplifier in dual-channel mode, and can load a minimum of 8 ohms in the bridge state, and can load a 2 ohm power amplifier in dual-channel mode, and can load 4 ohms in the bridge state. In the bridge state, only 8 ohm power amplifier can be loaded, and lower impedance cannot be loaded, otherwise the successful amplifier will be burned due to excessive current.

Frequency response 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 Smaller, indicating that the frequency response curve in the frequency range is flatter. If the frequency response range of the power amplifier is tested with -3 decibels, the sound from this power amplifier may not be so straight.

Damping coefficient: This is the ratio of the internal resistance of the power amplifier to the load impedance. The damping coefficient = the impedance of the speaker ÷ (the internal resistance of the power amplifier + the impedance of the speaker cable). The power amplifier with high damping coefficient can strengthen the control ability of the speaker unit, which can make the unit The response is closer to the requirements of the output signal of the power amplifier, but an excessively high damping coefficient will cause the low-frequency ductility of the speaker to deteriorate and the sound to be dry and hard. A relatively low damping coefficient can obtain soft bass, but a too low damping coefficient will cause the bass to become procrastinated and unclean. The general power amplifier damping coefficient is between 200-[email=1000@8]1000@8[/email] ohms. The quality of the speaker cable is not good, and the large resistance of the cable will also affect the damping coefficient of the power amplifier, which will weaken the control of the speaker and cause the sound to become dispersed.

Input sensitivity: This is a voltage concept, indicating that when the power amplifier reaches full power output, the signal voltage at the input end. The input sensitivity voltage of a general power amplifier is between 0.775v (0dB) and 1.5v (+6dB), the sensitivity voltage The higher the value, the lower the input sensitivity. Some high-quality power amplifiers have low input sensitivity due to the use of deeper negative feedback circuits, so they have lower distortion, wider frequency response and better sound quality.

S/NorSNRor Humand Noise: refers to the ratio of the signal voltage of the power amplifier to the noise floor voltage. The larger the value, the lower the noise of the power amplifier. Generally, the signal-to-noise ratio of professional products is around 100 decibels. When marked with a positive value, the higher the better (some power amplifiers are marked with a negative value, and the smaller the value is, the better). Attenuating the input level gain of the power amplifier (turning down the power amplifier volume knob) will reduce the signal-to-noise ratio of the power amplifier.

Second, the basic skills of buying audio equipment
Playing music without knowledge and equipment is like "talking on paper." Therefore, it is very important to choose a good set of audio equipment, but nowadays, the audio market has a mixed bag of speaker brands. How to find a suitable and reasonably priced audio equipment in the complicated market has left many people at a loss. The following editor will teach you some skills to identify the quality of audio equipment.

(1) Natural tone balance
First of all, the sound reproduction of the speakers should be real. The reproduced vocals and instrumental music should be as close as possible to the original sound without being distorted. The sound heard should be smooth and silent, without the strongest and weakest audible sounds. The midrange and treble should not be too loud or stubborn to let go. Can find some instrumental music with a wide frequency range (such as piano music) recordings to play. Pay attention to the changes in tone when listening to the 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 the sounds of different frequency bands in sequence. The bass should be compact, clear, precise in tone, not buzzing, muddy or ambiguous; the midrange, which is the main part of the music, is more important. The vocals and instrumental sounds should be natural, detailed, and not overly loud. It may be muffled, and it should not be too bright or too light. The high pitch should be open, airy and extensible, without screaming or fading.
Resolution: Listen carefully to see if you can hear the details of the music, such as the decline of cymbal or piano sounds, the hall sounds in concert halls or jazz clubs. If the low-level details are not clear, it means that the speakers lack transparency. In order to have a real and satisfactory playback effect, the resolution at low levels is essential. This is also the difference between a good speaker and a crappy speaker.
Transient response: The speaker should be able to reproduce the transient in music. The sound response when you just hit the drum or the guitar is strong and sound. It should not make people "surprised", "excited" or "slow" and "insensitive". In addition, natural fading sounds, such as the "tailing" of cymbals and voices, should gradually decay and stop abruptly.

(3) Sound environment of speakers
If you try to listen to speakers in an improperly placed audio store, it is unlikely that you will hear the full performance of the speakers. Because the placement of the speakers in the room is very important, even if the speakers are moved a few centimeters forward or backward, Will make the loudspeaker's low-frequency response have a greater change. When the speakers are 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, the speakers are not properly positioned, and the sound and image localization sound cannot be expected. Therefore, you should find an appropriate placement position for the speakers at home, so that the speakers can fully display their power and show their skills.

(4) Listen to familiar music
Since the sound quality of CD records is very relevant, there are good times, so when you go to the audio store to try out and buy speakers, it is best to bring a few more CD records that you are familiar with. Only in this way can you hear what is originally on the CD recording and what is held by the speakers.

Third, avoid the misunderstanding of audio usage
It is important to have a set of high-end equipment, but it is also important to use these equipment correctly. For now, among the general audio enthusiasts, there are some misunderstandings in use that should be avoided.
(1) Put the equipment in the cabinet. Some people put the equipment in a custom-made cabinet for decoration and protection. This will make the tone muddy due to the latent vibration caused by the space in the cabinet, and the power amplifier and other equipment are easy to overheat and age due to insufficient circulating air. If the speaker is installed on the wall, the sound effect will become blunt.
(2) Stacking equipment. Many people like to place video disc 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 camcorders and power amplifiers, which will make the sound harder and produce a sense of depression. The correct way is to put the equipment on the audio rack designed by the factory.
(3) The power plug is irrelevant. A good system for the positive and negative processing of the power plug has a clear tone and natural smoothness; the positive and negative are inconsistent or uneven, the tone will be hard and rough.
(4) The wiring is not firm and unclean. If the sound of the system is dry and hard, one of the reasons may be poor contact, such as a weak plug, oxidation of the contact surface, dust or oil stains, etc., so you should always check and keep the contact surface clean.
(5) The placement of speakers is "adapted to local conditions." Some people have other furniture in the room, so they adjust the position of the speakers to the furniture. The correct one should first determine the listening distance, and then place the speaker to 1/3 between the seat and the opposite wall. The distance between the speakers is 0.7 times the direct distance between the listener and the speaker, and the height should be equal to the listener’s ears and the tweeter. .
(6) Improper handling of wiring. Do not tie the power cord and the signal line together when handling the wiring, because the alternating current will affect the signal; the signal line or the speaker line must not be knotted, otherwise it will affect the sound; the signal line or the speaker line can be shortened if it is too long. Many signal lines have directionality, don't make mistakes.
(7) Take it for granted to deal with room acoustics. In addition to Mingyin and sound insulation, the more important thing is the treatment of sound wave reflection and refraction. This needs to consider the volume, size, sturdiness, use of materials, etc. of the room. If you are not an expert, even if the room is decorated luxuriously and beautifully, the sound is difficult to achieve best effect.
(8) Self-deception. If the equipment plays a certain type of music very well, while playing another type of music is not ideal, this indicates that the system has not reached the ideal level, and needs to learn more, listen more, and observe more to improve it.
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