Application of the main technical characteristics of the speaker system:
Speaker systems have a number of technical features that are directly related to the effects of the sound and the use of the application. In order to use these technical features, users must understand them.
(1) Two-way (two-way) and three-way (three-way) speaker systems
The spectrum of the audio signal is very wide. It is impossible to use a speaker unit with a 20Hz-20kHz signal to satisfy the entire frequency response. Generally, a large-diameter speaker unit of 12 inches or more has good bass characteristics and little distortion, but exceeds 1.5kHz signal, its performance is poor; the 12-inch tweeter unit (tweeter compression driver) above 3kHz reproduced signal performance is very good, but not in the midrange and bass reproduction signal. Therefore, there is a speaker system composed of various frequency response characteristic units. The two-channel speaker system consists of two units of bass (including mid-bass) and high-pitched (including middle and high-pitched), which are composed of bass, midrange and treble. The unit consists of a three-way system.
The two-way speaker system has a simple structure and a relatively low cost. In order to solve the lack of this intermediate audio frequency, some manufacturers have used a method of reducing the frequency, that is, moving the frequency response characteristic of the woofer upward on the crossover network. The tweeter is waiting for the frequency characteristics to move down. Another problem is that the crossover frequency can only be set between 500Hz and 2kHz, which is an important part of the vocal and music spectrum. Therefore, the auditory person left a "empty" feeling and the distortion heard. Because of this, the requirements of the three-way speaker for the speaker unit are relatively high. If the performance of the unit is not good, the sound of the entire speaker system is not smooth enough or there is serious phase distortion.
The characteristics of each unit of the three-way speaker system can be compromised, and their respective strengths can be fully utilized. The two crossover intersections can be selected at the upper and lower edges of the important parts of the midrange vocal and music spectrum, and have no effect on the sound quality. Therefore, the three-way speaker system reduces the distortion of the sound, improves the clarity of the sound, improves the performance of the cross-band between the low and high treble, and increases the power handling capability of the speaker system, thus being a performance, concert hall and opera house. The best choice for sound reinforcement systems.
(2) Sensitivity and maximum sound pressure level (SPL max)
The speaker unit is a transducer between the electrical signal and the sound, which is required to be converted to a very loud sound with a relatively small input power, which requires the speaker to have a higher sound pressure sensitivity, [sensitivity] In essence, it is a reflection of [conversion efficiency]. Due to the design techniques used in various types of speaker systems, the materials used and the production processes are different, and the sensitivity is also very different.
Sensitivity refers to the electric power input to the speaker unit of 1 watt, and the sound pressure level measured at a distance of 1 meter away from the speaker axis. If the sensitivity of the two speakers differs by 3 dB to achieve the same large sound pressure level output, it is necessary to increase the power. The input power is doubled, so a speaker with higher sensitivity can make a louder sound.
The input power capability of the speaker system is generally much larger than 1 watt (generally between 100 watts and 2000 watts). Therefore, the maximum allowable electric power can be input during actual use, at the rated maximum power, input to the speaker , in the speaker axis. The sound pressure level generated at 1 meter is called the maximum sound pressure level SPL max, sensitivity = 100dB, 1w/1m speaker , if the maximum power bearing capacity is 1000W, then SPL max = 100dB + 30dB = 130dB, 1m.
(3) Distortion and sound quality
The speaker factory does not have the distortion rate of their products. In fact, it is a very important technical parameter. The sound quality is a relatively abstract evaluation, and it is not possible to be nominal on the document. Only subjective listening comparison can be adopted, usually sensitivity. There is a contradiction with the sound quality. Manufacturers need to strike a proper balance between the two. Generally speaking, medium and low-priced products are dominated by sensitivity, pursuing performance and price ratio, while high-priced products are biased towards sound quality, and the highest level Both are both.
(4) Pointing characteristics of the speaker system
The sound emitted by the speaker is usually non-directional in the low frequency band (below 200Hz), and spreads evenly in all directions, but in the high frequency band, the sound is transmitted with strong directionality. This directional characteristic (all kinds of speakers) They are all different in our system design. The excellent constant pointing characteristics can concentrate the energy of the sound waves into the audience area during the site layout, avoiding the strong reflection surface of the sound waves and the sound field interfering with each other.
The directional characteristics of the loudspeaker make the sound pressure level deviating from the axial direction gradually decrease with the increase of the yaw angle, and the sound pressure level is attenuated in inverse proportion to the square of the distance with the increase of the acoustic wave propagation distance, which is far from the speaker. If the two attenuations are chosen properly, the two attenuations can be compensated for each other, so that the sound field is more uniform. Large projects require a relatively wide area, and a single speaker is usually not enough. It is necessary to combine a plurality of speakers into a speaker group (display), and in the display speaker system, the constant pointing characteristic can make the sound waves in the middle and high frequency bands between the speakers do not interfere with each other in the speaker, and use one with the above pointing characteristics. The speaker is arranged in a figure-eight shape, which can cover twice the single speaker. Otherwise, the sound has interfered 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 handling capability of the speaker system
Speaker power handling capability (also known as the rated power of the speaker) is an important technical parameters, which represents the speaker to withstand the power input capacity of long-term continuous safety work, understand the power handling capability of the speaker, you must first understand how the speaker driver is damaged, There are two modes of damage to the drive:
One is the overheating damage of the voice coil ( sound ring burnt, overheat deformation, inter-turn breakdown, etc.), and the other is that the displacement of the diaphragm of the drive exceeds the limit value, so that the cone diaphragm of the speaker / the elastic parts around it Damage, usually occurs in low frequency signals that contain many large amplitudes.
The sound signal is not a sinusoidal signal, but a random one. These random signals can be represented by three energy numbers. The effective value (RMS) is also called the rms value, which is the sinusoidal signal of the amplitude of the signal peak. The measurement results, close to the average value, basically represent the heating energy of the signal.
Peak (Peak) signal reaches the maximum level, for the sine wave, the peak level is greater than the RMS level 3dB, for music signals, the peak level exceeds the rms up to 10-15dB in assessing a loudspeaker The peak value is important when the displacement capacity is used. The peak factor is used to indicate the ratio of the peak level to the rms level. For a pink noise source, the peak factor is 6 dB, that is, the peak voltage is 4 times the rms voltage. .
The power processing capability of the speaker is the technical parameter measured under the condition that the processed pink noise signal is continuously added for 2 hours and the permanent change of electrical and mechanical properties is not more than 10%.
(6) Impedance of the speaker unit
The impedance of the speaker unit includes inductance, capacitance and resistance. The inductance and capacitance vary with frequency. Although the nominal impedance change in the speaker system is too large, it will affect the stability of the entire audio system. The DCD double-coil differential drive design changes the impedance to [pure resistance] and is unaffected by frequency changes, allowing the entire audio system to work stably.
How to improve the reliability of the speaker system
In daily life, even if the power matching of the amplifier and the speaker system is equivalent, the event of the speaker damage unit may occur due to:
1. Improper operation, the output power of the power amplifier is too large;
2. When the performance reaches a climax, the atmosphere in the venue is warm and the sound pressure needs to be increased. When the signal is increased, the microphone input signal is too large and the power amplifier is overloaded, and the distortion waveform generates a large number of harmonics, which damages the tweeter;
3. The microphone produces strong acoustic feedback and howling, the amplifier is strongly overloaded, and the speaker system is damaged.
To this end, modern new speaker systems have adopted a variety of protective measures, which can be divided into two categories:
1. Improve the heat dissipation of the speaker unit so that it does not overheat damage when overloaded;
2. Install a limiter protection device in the speaker box. When the drive power and peak level exceed the rated value of the speaker , the limiter blocks the voice coil with a non-linear resistor (bulb).
These measures improve the speaker 's ability to resist overload, but also affect the dynamic range of the sound, making the range not wide enough, and the tone is blurry and dim. Therefore, the best way is to take measures on the amplifier so that its output does not cause clipping and power overload.
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