Weak current College】 【how to select the speakers --- Power By】 【China power house network.

<br> The speaker is actually a put to wide audio power signal transducer (loudspeaker), put it into enough sound pressure level of the sound can be heard. To correctly select a good speaker, you must first understand the properties of a sound signal ., and then ask the speaker to the "authentic" and audio signals into realistic nature sounds. <br> The human voice and the music is a random signal, the wave is very complex. You can listen to the sound frequency range usually ranging 20Hz .-20kHz; language of the spectrum range around about 150Hz-4kHz; and various music spectrum range up to around 40Hz-18kHz. Its average spectrum of energy distribution: bass and bass parts most, some times in the treble, the treble section minimum ( .about as part of the energy in a, bass 1 / 10); the energy of the human voice is concentrated mainly in 200Hz-3.5kHz frequency range. They can listen to the sound random signal amplitude peak average than it is about big 10 - .15dB (or even higher). Therefore the speakers to correctly release these random signal again, ensure the replay sound sweetly, speakers must have broad frequency response, enough sound pressure level and dynamic range of signal. <br> <br> We hope to .be able to use relatively small signal power input gain enough sound pressure level, requiring the speakers have a high-efficiency power conversion into a sound pressure sensitivity. Also called speaker system in the input signal is just the right amount of overload, would not be .damaged, that is to have a high reliability. <br> <br> Speaker system the main technical characteristics of the application: <br> <br> The speaker system has many and tone effects and applications directly related to the technical characteristics, in .order to make the best use of live these technical characteristics, the user must know something about them. <br> <br> 1) 2nd Road (second Division) and three-way (three frequency) speaker system <br> <br> .Audio signal spectrum range is wide, the 20Hz-20kHz signal to a speaker unit is unable to meet the whole length frequency response; more than average 12 inch large diameter speaker unit, bass performance is very good, distortion is not big, but more than .the signal, it 1.5kHz behaving badly; 1-2 inches of the treble speaker unit (treble compressed drives) replay 3kHz above signal performance was good, but cannot replay baritone and bass signal. So they have a frequency response from the various modules of .the speaker system, the bass (bass) and treble (treble) made up of two units are called two-channel speaker system, bass, tenor and treble three modules known as three-way system. <br> <br> 2-way .speaker system structure is simple, and relatively low cost, in order to address the lack of audio in this paragraph, then the rate of manufacturers with a folding failure, that is in the crossover network on bass unit of frequency response up to treble unit waiting .to move down the frequency characteristic. Another problem is that the crossover frequency can only be set at the intersection of 500Hz-2kHz regional, and this is what the human voice and the music is an important part of the spectrum. Therefore in the hearing on .the left are "empty" and hear distortion. Also because of this, three-way speaker on driver demand relatively high, if the unit's performance is poor, the voice of the speaker system is not smooth, or have serious phase distortion. <br .> <br> 3-way speaker system unit characteristics may not compromise, giving full play to their strengths, the intersection of the two frequency in the Alto voice and optional music spectrum important parts of the upper and lower edges, has no effect on the .sound quality, 3-way speaker system reduces sound distortion, raised his voice clarity, improved low high and treble cross band performance, increase the power of the speaker system, so the processing power is theatrical performances, concert hall and Opera House, the best .choice for sound reinforcement systems. <br> <br> 2) sensitivity and maximum sound pressure level (SPLmax) <br> <br> Speaker unit is a form of electrical signals and sound between the transducer and request it to be relatively small input .power conveyed into a rolling sound, this requires that the speaker has high sound pressure sensitivity, [sensitivity] is essentially a [conversion efficiency], plus various Yang losses due to the use of the system design, selection of materials and production processes, and .other aspects of difference, sensitivity are large. <br> <br> Sensitivity refers to the input 1 Watt loudspeaker unit power, leave the speakers axis 1 m distances measured sound pressure level, if the sensitivity of the two speakers differ by 3dB to achieve .the same high sound pressure level output, you need to increase the electrical input power is doubled, so sensitivity higher speakers can make a considerable amount of sound. <br> <br> Speaker system input power capacity is generally much greater than 1 Watt ( .generally at 100 Watt-2000 watts) therefore actually used can enter the maximum permissible power for the rated maximum power, type speaker, speaker axial 1 m resulting sound pressure level is called the maximum sound pressure level SPLmax cases, sensitivity = 100dB, 1w / .1m speakers, with maximum power capacity to 1000W, SPLmax = 100dB + 30dB = 130dB, 1m. <br> <br> 3) distortion and sound quality <br> <br> Speaker factory have nominal rate distortion of their products, in fact .it is a very important technical parameters, quality is a relatively abstract evaluation, there is no possible in superscripts, only the file take subjective listening test, usually, the sensitivity and the sound quality is contradictory, manufacturers need to strike a proper balance in, .generally speaking, the price of the product, are driven by sensitivity, the pursuit of cost performance, and high-priced product-neutral sound quality, and the highest level is a combination of both. <br> <br> 4) [character .] and [common] <br> <br> In this once again cited out another relatively abstract and subjective evaluation of audio, sound reinforcement, unlike at home of Hi-Fi audio equipment, have compatibility is very high, because each site may show .different types of programs, from Opera to rock concerts, Also possible is to report the signal-based language, so the sound system must be compatible with the different program source, do [average of] the superior is not biased to a particular one and .home Hi-Fi audio equipment, only need to take care of a person or a small group of people, their product is to allow the [character] exists, but as a professional sound reinforcement systems equipment, the [character] will become [limitations .], or [defect]. <br> <br> Professional sound amplifying equipment needed for a large group of public services, programme content often transform, [General] are the basic requirements for a stronger, compatibility, different kinds of programs must have .[average] performance, in addition to this, the professional sound reinforcement equipment must be "no rendering", "no exaggeration", "true" to restore the sound source is [common] or [common sexual]. <br> <br .> 5) speaker system point to properties <br> <br> The speaker sound is usually in the low frequency band (below 200Hz) voice is not directional, spread evenly in every direction, but in the high frequency band, the sound propagation render .strong direction, this points to a character (various speakers are not the same) is what we in the system to be applied, the excellent characteristics of constant to point to the site layout when Sonic Energy focus to the audience area, avoid strong reflection surface .acoustic wave and acoustic field interfere with each other. <br> <br> The speaker's point to properties that deviate from the axis of the sound pressure level with the deflection angle increases gradually decrease the sound pressure level, sound pressure level and with Sonic distance .increases as the square of the distance and decay is inversely proportional to the distance from the speaker and the position of the different audiences district, will select the two attenuation, you can make the proper two kinds of decay mutual compensation, thereby enabling a more uniform .sound field, large projects need cover relatively wide range, single-only speakers are often inadequate to meet the needs of the many speakers spell synthesis speaker Group (display), and in the display speaker system, the Hang Seng index to feature allows speakers between .medium and high frequencies of sound waves in the speaker room do not produce mutual interference, use the above links to properties with a pair of speakers is composed of eight glyphs display, you can override the individual speakers, otherwise, the sound in speaker front already .interfering seriously affect the sound field of uniformity and clarity of the sound. <br> <br> 6) speaker system power handling capability <br> <br> Speaker power handling capacity (or the speaker of the rated power) is an important parameter .that represents the speaker stand long continuous security of power input capabilities to understand the speaker's power handling capability, you must first understand how damaged speakers drive, drive damage model has two kinds: <br> <br> One is the voice coil heat damage ( .voice coil burn, overheating deformation, circle room breakdown, etc.), and the other is drive diaphragm displacement exceeding limit values, so that speakers of conical diaphragm / or its surrounding elastic part is damaged, often containing many large amplitude and low frequency signals .. <br> <br> The sound signal is not a sine wave signal, but a random, these random signal available three can count to indicate that a valid value (RMS) also known as RMS value is to signal peak amplitude sine signal measurement .results, close to the mean, basically, on behalf of the signal of heating energy. <br> <br> Peak (Peak) is the signal reaches the maximum level, for a sine wave, peak level greater than valid values for the music .signal 3dB, peak level valid value of up to 10-15dB in assessing a speaker's movement capability, the peak is important, crest factor, used to illustrate the peak and RMS level of the ratio, for press AES2-1984 pink noise source, crest .factor, for 6dB peak voltage is 4 times the RMS voltage. <br> <br> Speaker power handling capacity by (AES2-11984) of pink noise signal continuous plus 2 hours of work, its electrical and mechanical properties of permanent change of not .more than 10% of the measured parameters. <br> <br> 7) load (heated) after the sound pressure level (also known as power compression) <br> <br> All product specifications are marked that power all manufacturers of custom .is speaker at the manufacturer selected test signal and the best value under the conditions, when the speaker into the work status (for example, equal to or greater than the full power of 20 seconds), voice coil and magnet heating temperature rise after, because .of their performance has changed the original heated front unit characteristics, this time, the actual sound pressure output will reduce, conventional speakers, such as voice coil temperature 60 ° -80 °, common rating sound pressure drop 3dB for tolerance, such as the excellent .voice coil cooling, temperature up to 100 degrees or more, the actual sound pressure drop of up to 6-8dB, this is very alarming decline, such as former titles and a doubling of the speaker only enhance the sound pressure level 3dB if speaker sound .pressure level dropped to bridge up to 6dB, so much sound pressure level must be reduced from the original one speaker increased to four, sorry, audio industry not nominal decline such a sound pressure level, you must close to improve the thermal design of loudspeaker unit .. <br> <br> 8) speaker cell impedance <br> <br> The impedance loudspeaker unit including, inductance, capacitance and resistance, inductance and capacitance changes with frequency, while winning the speaker system that an impedance changes too large, it .will affect the stability of the entire sound system, JBL's new DCD double coil difference driven design is the impedance becomes [pure resistance], are not affected by changes in the frequency, the entire sound system stability. <br> <br> How to .improve the reliability of the speaker system <br> <br> In daily life, even in the amplifier and speaker system power matching certain circumstances also occur in young cells become damaged, losses plus, their reasons are: <br> <br> 1 .. improper operation, power amplifier output power is too large <br> <br> 2. show climax when a warm atmosphere, the need to enhance the sound pressure, increase the signal, the microphone input signal too much cited amplifier overload clipping, a .large number of harmonic distortion of waveform generation, and damaged the treble unit <br> <br> 3. microphone strong acoustic feedback whistling, PA strongly damaged speaker system overload, as this isGeneration of a new speaker system to take a variety of protective measures ., these measures can be divided into two categories: <br> <br> 1. improve the thermal power loudspeaker unit so that it does not occur when the overload, overheat damage <br> <br> 2. the speaker box install limiting protection .device, when the motor power and peak over the speakers of the ratings, the limiter to exceed the power level using a nonlinear resistor (bulb) to block the voice coil. <br> <br> These measures increase the capacity of the speaker on .overload, but also influenced the sound of dynamic range, the range is wide, timbre feel fuzzy and bleak. <br> <br> Therefore, the best approach or amplifier measures so that its output is not generated clipping and power overload etc. < .br>.