1, two-way (two-way) and three-way (three-way) speaker 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 manifestation of [conversion efficiency], and various types of Yang loss are smooth. Due to the design techniques used, the materials selected and the production process, 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. It is also impossible to mark the file. Only subjective listening can be used. Usually, Sensitivity and sound quality are contradictory. 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. The level is both.
4, [personality] and [common]
Here again another relatively abstract and subjective performance evaluation, sound reinforcement, different from the Hi-Fi audio equipment in the home, must be very compatible, because each venue may perform different types of programs From opera to rock concerts, it may be just a speech report based on language signals. Therefore, the sound system must be compatible with different program sources, so that the [average] excellence can not be biased on a certain purpose, but at home. Hi-Fi audio equipment, only need to take care of the taste of a person or a small group of people, the [personality] of the product is allowed to exist, but as a professional sound reinforcement system equipment, this [personality] will become [limited] Sex] or [defect].
Professional sound reinforcement equipment needs to serve a large group of public, and the content of the program often changes. [Common] is the basic requirement, compatibility is strong, and programs of different natures must have [average] performance. In addition, professional sound reinforcement equipment must It is "no rendering", "no exaggeration", and "faithful" to restore the sound source, which is [commonity] or [commonity].
5, the 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.
6, the power handling capabilities of the speaker system
The power handling capability of the speaker (or the rated power of the speaker) is an important technical parameter. It represents the power input capability of the speaker to withstand long-term continuous safe operation. To 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 is the maximum level at which the signal reaches. For sine waves, the peak level is greater than the rms level by 3dB. For music signals, the peak level exceeds the rms value by 10-15dB. 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 according to AES2-1984, the peak factor is 6 dB, ie the peak voltage is valid. 4 times the value voltage.
The power processing capability of the speaker is the technical parameter measured in the case where the pink noise signal processed by (AES2-11984) is continuously added for 2 hours and the permanent change in electrical and mechanical properties is not more than 10%.
7. The sound pressure level drops after loading (heating) (also known as power compression)
The nominal power on all product specifications is custom-made by each manufacturer. It is the best value of the speaker under the test signal and conditions selected by the factory. When the speaker enters the working state (for example, equal to or greater than 20 seconds of full power), After the temperature rise of the voice coil and the magnet, 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, and the conventional speaker, such as the voice coil temperature rise of 60 degrees - 80 degrees, is common. The rated sound pressure level drops by 3dB as the tolerance. For example, the voice coil has excellent heat dissipation, the temperature is up to 100 degrees, and the actual sound pressure drops by 6 to 8dB. This is a rather amazing drop, as in the previous question, and doubled. The speaker only raises the sound pressure level by 3dB. If the sound pressure level of the speaker drops by 6dB, it must be increased from the original one to four to compensate for such a large sound pressure level. Unfortunately, the sound industry has no nominal sound pressure level. Falling, it is necessary to improve the heat dissipation design of the speaker unit.
8, the 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.
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