The Basic Knowledge Of Sound Is Popular-speaker Technology

- Mar 06, 2020-

The speaker system has many technical characteristics that are directly related to the sound effect and use occasions. In order to make full use of these technical characteristics, the user must understand them.

① 2nd and 3rd

The frequency spectrum of audio signals is very wide. It is not possible to use a speaker unit for the signal of 20Hz-20kHz to meet the entire frequency response. Generally, large-diameter speaker units of 12 inches or more have good bass characteristics and low distortion, but they exceed 1.5kHz signal, its performance is very poor;

The 1-2 inch tweeter unit (treble compression driver) reproduces signals above 3kHz, but it cannot reproduce midrange and bass signals.

So there is a speaker system composed of various frequency response characteristics units. The two-way speaker system is composed of two units of bass (including midrange) and treble (including midrange and treble). This kind of unit is called a three-way system.

② Sensitivity and maximum sound pressure level

The speaker unit is a transducer between electrical signals and sound. It is required that it can be converted into very loud sound with relatively small input power. This requires the speaker to have high sound pressure sensitivity. The sensitivity is essentially It is a reflection of conversion efficiency. Due to various differences in design technology, selected materials and production processes, the sensitivity of various types of Yangshun system is also very different.

Sensitivity refers to the electrical power of 1 watt input to the speaker unit. The measured sound pressure level is 1 meter away from the speaker axis. If the sensitivity of the two speakers differs by 3dB, the same sound pressure level output is required. The input power is doubled, so louder speakers can produce louder sounds.

③Personality and commonality

Here again, another relatively abstract and subjective performance evaluation is made. The sound used for sound reinforcement is different from the Hi-Fi audio equipment at home. It must be highly compatible because each venue may perform different types of programs. From operas to rock concerts, it may also be just a speech conference mainly based on language signals. Therefore, its audio system must be compatible with different program sources, so that the average performance is excellent, that is, it cannot be focused on a certain purpose. -Fi audio equipment only needs to take care of the taste of one person or a small group of people. The personality of its products is allowed to exist, but as a professional sound reinforcement system equipment, this personality will become a limitation or defect.

④Direction characteristics

The directivity of the speaker makes the sound pressure level off-axis gradually decrease with the increase of the deflection angle, and the sound pressure level decreases with the increase of the sound wave propagation distance and is inversely proportional to the square of the distance. For audience areas with different orientations, if these two attenuations are selected properly, the two attenuations can compensate each other, so that the sound field is more uniform. Large-scale projects need to cover a relatively wide area. A single speaker is usually not enough to cope. Multiple speakers need to be assembled into a speaker group (array). In the array speaker system, the constant directivity characteristic can prevent the sound waves in the middle and high frequency bands between the speakers from interfering with each other. The speakers are arranged in a figure shape, which can cover twice the single speaker. Otherwise, the sound will interfere with each other in front of the speaker, which seriously affects the uniformity of the sound field and the clarity of the sound.

⑤ Power processing capacity

The speaker's power handling ability (or the rated power of the speaker) is an important technical parameter. It represents the power input ability of the speaker to withstand continuous and safe working for a long time. To understand the speaker's power handling ability, we must first understand how the speaker driver is damaged. There are two modes of drive damage:

One is the overheating and damage of the voice coil (the voice coil is burnt, overheated and deformed, and the inter-circle breakdown, etc.).

The other is that the displacement of the diaphragm of the driver exceeds the limit value, which damages the cone diaphragm of the speaker / or the elastic parts around it, which usually occurs in low frequency signals containing many large amplitudes.

⑥ The sound pressure level decreases after loading (heating)

The nominal power in all product manuals is self-determined by each manufacturer. It is the best value of the speaker under the test signal and conditions selected by the manufacturer. When the speaker enters the working state (for example, after 20 seconds equal to or greater than the full power), After the voice coil and magnet are heated and the temperature rises, the original characteristics of the unit before heating are changed due to their performance degradation. At this time, the actual sound pressure output will be reduced. Conventional speakers, such as the voice coil temperature rise 60 to 80 degrees, are common. The rated sound pressure level is reduced by 3dB as a tolerance. If the voice coil is excellent in heat dissipation, the temperature can reach more than 100 degrees, and the actual sound pressure drop can reach 6 to 8dB, which is a quite amazing drop. Doubling the speaker only increases the sound pressure level by 3dB. If the sound pressure level of the speaker drops by 6dB, it must be increased from one speaker to four to compensate for such a large drop in sound pressure level. Unfortunately, the audio industry has not claimed To reduce the sound pressure level, it is necessary to improve the heat dissipation design of the speaker unit.