Selection of speakers

The speaker system has a number of features that are directly related to the use of sound effects and the use of the occasion. In order to make good use of these technical characteristics, users must be aware of them.
　　(1) two and three speaker systems
　　Audio signal spectrum range is very wide, to the 20Hz-20KHz signal with a loudspeaker unit is unable to meet the whole section of the frequency response; general more than 12 inch large-diameter speaker unit, bass response is very good, little distortion, but more than 1.5khz signal, it is sent; 1-2 inches tweeter unit (treble compressed drive) replay 3kHz above the signal performance is very good, but cannot replay the tenor and bass signal. And then there are the speaker system composed of various frequency response characteristics of the unit, by bass (bass) and Soprano (ALT) composed of two units called Lu Er speaker system, composed of bass, midrange and treble three unit known for three road system.
　　Two way loudspeaker system structure is simple, the cost is relatively low, in order to solve the lack of the midrange frequencies, so some manufacturers used a bending failure method, namely in the crossover network to the frequency response of the woofer to move on, the treble unit remains to be seen whether the frequency characteristics is moving downward. Another problem is that the frequency crossover frequency can be set between the 500Hz-2kHz. And this area is an important part of the spectrum of vocal and music. So in the sense of hearing people left "empty" feeling and heard the distortion. Also because of this, the three speaker on the speaker unit requirements are relatively high, if the unit is not good, the entire speaker system is not smooth enough sound, or a serious phase distortion.
　　Of each unit of the three-way speaker system characteristics without compromise, give full play to their respective strengths, the two frequency cross points are optional in the alto voice and music spectrum is an important part of, at the lower edge, the sound without any influence, so three-way speaker system reduces the distortion of sound, so as to improve the clarity of sound, improved between low and high treble cross band performance, increase the loudspeaker system power handling capability, and therefore is best choice for theatrical performances, concert halls and opera houses of sound reinforcement system.
　　(2) sensitivity and maximum sound pressure level (SPL max)
　　Speaker unit is between an electrical signal and sound transducer, and demands that it with a relatively small input power convey replaced with a loud voice, this requires that the speaker has a higher sound pressure sensitivity, sensitivity [] is essentially is a conversion efficiency of embodied, all kings of loudspeaker system because the technology to design, selection of materials and production processes and other aspects of difference, a large difference in sensitivity.
　　Sensitivity refers to the input speaker unit 1 watts of electrical power, in the direction of the speaker axis 1 meters away from the sound pressure level, if the sensitivity of the two speakers to reach the same large sound pressure level output, need to increase the power of the input power, so the higher the sensitivity of the speaker can emit a loud sound.
　　The input power capacity of the speaker system is generally far greater than 1 watts (usually between 100 watts -2000) so the actual use can be entered into this maximum allowable power, with the maximum power, input speakers, the sound pressure level of the speaker's axial 1 meters is called the maximum sound pressure level Max SPL case, the sensitivity =100dB, 1w/1m speakers, if the maximum power of 1000W SPL, max=100dB+30dB=130dB 1m.
(3)Distortion and sound quality
　　Speaker factories are not the nominal products they rate distortion, in fact, it is a very important technology parameter, and the sound quality is a more abstract evaluation, nor may the document nominal, can only take subjective listening competition, usually sensitivity and sound quality is contradictory, producers need to make a proper balance between the two, generally speaking, low-cost products, sensitivity to play the leading role, the pursuit of performance to price ratio, and high priced products stresses quality, and at the top of the hierarchy is both.
　　(4)Pointing characteristics of speaker system
　　The sound of the loudspeaker is usually in the low frequency range (below 200Hz). The sound is transmitted in different directions, but in high frequency range, the sound is transmitted in a strong direction, which is used in the system design.
　　Pointing to the characteristics of the speaker to the sound pressure level away from the axis with the angle increases and the sound pressure level decreases gradually, while the sound pressure level increased with the increase of the propagation distance and sound wave according to the inverse square of the distance from the speaker and attenuation, distance and range of different audience area, if these two attenuation can make the right choices, two the attenuation compensate each other, so that the sound field is more uniform, large projects need to cover relatively wide area, the only sound is usually not enough, need to be more than just speakers together group (Chen Lie), speaker Chen Lie in loudspeaker system, constant directivity can make the acoustic speakers between the high frequency interference, not in the box, with a pair of speakers with the directional characteristics of composition of eight shaped display, double, can cover a single speaker or sound, has been doing in front of each speaker Interference, which seriously affects the uniformity of the sound field and the clarity of the sound.
　　(5)Power handling capability of speaker system
　　The speaker's power handling capability is an important technical parameter, which represents the speaker's ability to withstand long-term continuous safety work, understand the speaker's power handling capability. First, we must understand how the speaker driver is bad, and the driver's damage mode has two kinds:
　　One is the voice coil overheating damage (voice coil burned, over heat distortion, the ring breakdown, etc.), and the other is the drive of the diaphragm displacement exceeds the limit value, so that the speaker's conical diaphragm / or its surrounding elastic parts damage, usually occurs in the low frequency signal contains many large amplitude.
　　Sound signal is a sine wave signal, but a random, these random signals available three to numbers, effective value (RMS) also known as root mean square value, is to a measurement result of signal peak amplitude of the sinusoidal signal, which is close to the average value, basically representative of the signals of the heating energy.
The peak value (Peak) is the maximum signal level, for the sine wave, the peak level is greater than 3dB, for the music signal, the peak level is more than the effective value of 10-15dB in assessing the displacement of a speaker, the peak value is used to indicate the ratio of peak level and RMS, peak factor is 6dB, that is, the peak voltage is 4 times the RMS voltage.
　　Speaker power handling capability is according to the pink noise signal processing for 2 hours after the electrical properties and mechanical properties of permanent change little under 10 per cent of the measurement of technical parameters.
　　(6)Impedance of speaker unit
　　The impedance of the speaker unit includes, inductance, capacitance and resistance, inductance and capacitance are varied with frequency, although the nominal impedance of the speaker system is too large to affect the stability of the whole sound system. The new DCD JBL dual line differential drive is designed to make the whole sound system stable.
　　Three: How to improve the reliability of speaker system
　　In daily life, even in the case of power amplifier and speaker system to match the case of the case of a speaker damage, the reasons are:
　　1. Improper operation, power amplifier output power is too large;
　　2. When the performance reached a climax, the atmosphere is warm, the need to improve the sound pressure, in the increase of signal, the microphone input signal is too large to overload the power amplifier, the distortion of the waveform generated a large number of harmonics, damage to the high;
　　3. The microphone has a strong acoustic feedback whistle, power strong overload, damage the speaker system.
　　To this end, the modern new speaker system to take a variety of protective measures, these measures can be divided into two categories:
　　1.Improve the radiating power of the speaker unit to make it less heat damage during overload;
　　2. In the speaker box installation limiting protection device, when the driving power and peak levels exceeded the speaker ratings, the limiter to over power level with nonlinear resistance (lighting) of the voice coil block.
　　The measures to improve the anti overload capacity of the speaker, but also affected the dynamic range of a sound, the range is not wide enough, sound feeling fuzzy and dim.
　　Therefore, the best way is to take measures on the power amplifier, so that the output does not produce the problem of clipping and power overload.