Speakers of the main technical characteristics and applications

Speakers (or speaker) is the mouthpiece of the audio system, has a direct impact on the quality of sound reproduction, is the sound system is one of the most crucial part. Speaker's power is an audible range audio signal transducer (loudspeaker) to have enough sound pressure level of the sound can be heard. How can you accomplish more with shovel this translation? you must first understand the properties of the sound signal, secondly to learn and familiarize yourself with the main technical characteristics of the speaker, the correct choice of good speakers. Sound signal properties mainly refers to the human voice, music and sound effects. The sound signal is a random signal, the wave is more complex, but in the case of human ears to hear the sound frequency range (20Hz ~ 20kHz), in which the voice of the spectrum range around 150Hz ~ 4kHz; various musical spectrum range 40Hz ~ 18kHz. Average spectral energy distribution: bass and bass parts in the largest part of the second in the treble, the treble section minimum (about energy and the bass part 1/10 of the human energy is concentrated mainly in 200Hz to 3.5kHz frequency range). The audible sound random signal amplitude peak average than it is about a 10 ~ 15dB. Therefore, to properly to evolve these random signal to ensure playback signal sound sweetly, speakers must have broad frequency response, enough sound pressure level and signal dynamic range with high-efficiency power conversion into a sound pressure sensitivity. The speaker system has a lot of sound effects and applications directly related to technology, health, and to make the best use of live these technical characteristics, we must have a certain understanding. Frequency-division system for broadcast, film, television, theatre, dance halls, conference rooms, sports sites use speaker frequency system, (ii) the frequency, (3) three crossover system. Audio signal bandwidth from 20Hz ~ 20kHz, single-use a speaker unit is unable to meet the entire band of frequency response, in other words, to use a speaker unit to the frequency 20Hz ~ 20kHz uniform replay is most unlikely. For example, the diameter of 12-inch speaker unit, better low-frequency characteristics, distortion is not big, but more than signal, 1.5kHz its responsiveness is very bad. On the contrary, 2-inch-diameter speaker unit, replay 3kHz above audio signal response is good, but cannot replay baritone and bass signal. They must be made by the various frequency response unit consisting of a speaker system to complete broadband audio playback tasks. For example, the bass, treble and two modules of 2 loudspeaker system, bass, tenor and treble three modules of 3 loudspeaker system. II loudspeaker system structure is simple, but not in the band's response was very satisfactory. In order to address in the band's response, manufacturers take a compromise, the bass unit of frequency response up, and the treble unit of frequency response down to crossover point to setting between the 400Hz to 1500Hz (Figure 1 is a high-frequency range frequency response for down, move results). Crossover intersection often have a settlement, when the actual application may be based on the information provided by the manufacturer, in crossover intersection parts use the equalizer to improve according to actual needs. Figure 1 intersection in 400Hz. 3 loudspeaker system unit of frequency response is not compromised, can give full play to their strengths, the intersection of the two frequency is selected in the Alto voice and music spectrum important parts of the upper and lower edges, the sound quality does not have any impact. Intersection of settlement can adjust Equalizer is resolved. Second frequency, 3 loudspeaker system is broadcasting, film, TV, concert hall, Opera House, conference rooms, gymnasium. Three loudspeaker features a low distortion, high definition, the intersection between the bass and treble frequency band performance, frequency response frequency bandwidth, the speaker system of power handling capability, and speaker system is not easy to damage. Speaker unit is a form of electrical signals and sound between the transducers. The speaker system of the "sensitivity" is essentially a kind of "conversion efficiency", how to relatively small input power into a very loud sound, depending on speaker system conversion efficiency, i.e. by the sensitivity level of the speaker system. Due to the design, selection of materials and production skills and production process, and many other differences, differences in sensitivity is enormous. Speaker sensitivity refers to the supply of electric power loudspeaker unit 1W, leave the speakers axis direction 1m premises measured sound pressure level size. High sensitivity over the speakers of 100dB above. General is the high sensitivity of speakers equal sound great, if a and b the difference between the two speakers of sensitivity 3dB sound pressure level, to achieve equivalent sound pressure level output, sensitivity lower speaker doubled power input, or decrease the sensitivity level of the speakers doubled power input. People may be concerned about two identical sound pressure level for the speakers together, their synthesis of sound pressure level? we set the sound pressure level is the same two sound 80dB while together appear (80dB equivalent to loud vocal body when away from the sound pressure level 1m Department). It's synthetic sound pressure level is not a 160dB, which greatly exceeded the human ear can bear 120dB limit. So how much should a dB? this can sound energy law of superposition press log operations to figure out the result: because the overall sound pressure level Lp = 10Lgn + 20Lp Pe/P0 (dB). Here, we set the sound pressure level is the same two sound 80dB while together, on the equation in n = 2, 20Lg Pe/P0 = 80dB. So overall sound pressure level LP = 10Lgn + 20Lg Pe/P0 = 10Lg2 + 20LgPe/P0 = 3 + 80 = 83 (dB) for the same reason, if we set a sound pressure level with three voice 80dB while together, then the equation of n = 3, 20Lg Pe/P0 = 80dB, otherwise the total sound pressure level Lp = 10Lgn + 20LgPe/P0 = 10Lg3 + 20 Lg Pe/P0 = 4.77 + 80 = 84.77 (dB) sound engineering often encounter examples: a sensitivityFor the speaker, 99dB unit price $, another just 90dB, price only $ 5000, sensitivity to 99dB speaker, although the price is high, but the conversion efficiency is high, loudness, sensitivity to 8 only 90dB sound overall sound pressure is the loudness, 99dB 5000 × 8 = 4 (million), plus the eight power amplifier costs well in excess of 2 million, so generally choose speakers more cost-effective high sensitivity. Listed below are a set of speakers and synthesis of sound pressure level, for reference: the number 1 only 2 speakers only 4 only 8 only 16 å SPL (sound pressure synthesis) 90dB 93dB 96dB 99dB 102dB practice, the speaker system of the input power is far greater than 1W, generally from 50W to 2000W or greater, so the work can enter the maximum allowed power (usually the largest bear power loudspeaker 1.5 times best). To enter the rated maximum power, speaker speaker, axial 1m Department resulting sound pressure level is called the maximum sound pressure level SPL max. For example: sensitivity = 100dB, 1W/width speaker, if the maximum power capacity to 1200W, then its maximum sound pressure level SPL max = 100 + 30.8 = 130.8 (dB). Work must not pursue efforts and fills up the bass power, the ideal is 80% power output, audio engineering can increase the subwoofer speaker to enhance the low frequency sound especially drum musical instruments. While the radio, television, movies, listening to the general use of the Professional with high, medium, and low (bass speaker tray 15 inch) three frequency of speakers, their audio effect of frequency response has been very good. Speaker system power handling capability and power compact speaker system power handling capacity on behalf of the speakers under long-term continuous security work power input capacity, also known as speakers rated input power. Understand the speaker's power handling capabilities, you must understand how the speakers drive is damaged, drive damage model has two kinds: one is the voice coil heat damage (voice coil burn, thermal deformation, circle room breakdown short circuit, etc.), and the other is the drive of the diaphragm or the surrounding elastic part is damaged. This mainly occurs in the regular full-load work and large amplitude and low frequency signals for treble trumpet was mainly due to the strong positive feedback signal. So 100% of the power output and power amplifier power several times the largest bear power loudspeaker, speaker of the voice coil is very easy to be burned, speaker of the conical diaphragm can easily be damaged. Usually the sound signal is not a pure sine wave signal, but a random signal. Random signal can be used, on average, the RMS (root mean square), the third argument indicates the peak. Valid values are very close to the average signal fever it determine the energy base, for a sine wave signal peak is greater than the effective level of 3dB, music signals, peak may exceed the valid values for the flat up to 10 ~ 15dB, peak is the signal to reach the maximum levels, peak factor sometimes used to describe the peak level and ratio of RMS level, if the peak factor to 6dB, that is, the peak is the RMS level of 4 times. For example there is a sound indicators subject written by AES or IEC, rated input power: 600W peak as 2400W, enter 1200W, peak 4800W, rated input power: 75W, 250W, peak 300W, 1000W, 4 x between 6dB. The so-called speaker power compression, speaker after loading (heated) decreased performance of the sound pressure level. All products of the nominal power is the speaker manufacturer selected test signals and test conditions best value under test. In fact, when the speaker has entered the work status (equal to or greater than the full power of 20 seconds), voice coil and magnet heated and their performance degradation and changed the original heated front unit, this time of the actual characteristics of the sound pressure level output will reduce. Normally, the speaker voice coil heated warming 60 ℃ ~ 80 ℃, rated sound pressure drop 3dB for tolerance, such as voice coil cooling very superior, more than 100 ℃, the actual sound pressure level decreased by 6 ~ 8dB. As described before, plus a number of times before upgrading 3dB speaker, sound pressure level, 6dB need 4 speakers, 8dB will add 8 only speaker, if manufacturers do not indicate a decline of sound pressure level, so we're going to buy the manufacturers carefully sound. In no way, we need to consider when using the speaker good ventilation conditions, in particular the broadcasting, film, TV, use of monitoring systems, it is necessary to pay attention to maintain its high-quality technical performance, guarantee perfect sound quality. Speaker system to point to the characteristics of the speaker system is important to the characteristics of a specification. For broadcast, film, TV recording, listening system, control room acoustic design criteria, and application areas (listening coverage) is not very large, so the speaker system configuration changes, point to properties of the request is not prominent, but as a large conference rooms, theaters, stadiums these sound engineering system, due to the sound of the coverage area is large, the speaker system to point to the character index is important. Speakers point to properties, refers to the speaker sound in all directions to the space of sound pressure distribution and status. In General, the speaker is always a certain direction and the change of the frequency will change, usually in the low frequency band (below 200Hz) voice is not directional, and in the high frequency band, the sound is a strong direction, and the rest spread evenly in every respect. Speaker directivity can also be used radiation beam stenosis, beam narrower, radiation angle. Radiation angle or beam width, is the directivity pattern of sound pressure level and spindle-3dB (some standard-6dB, write-3dB is calculated according to the power, and is subject to write-6dB to sound pressure level calculated) point of view, as in Figure 3. Figure 3 off-axis orientation of the sound pressure level with the deflection angle increases gradually reduced. Although the speaker's point to properties make off axis of sound pressure level with the deflection angle increases gradually decreases, but at the same sound pressure level will vary according to the acoustic wave propagation distance increases as the square of the distance attenuation: inversely to double attenuation 3dB decay 2 times increase 6dB increase 3X 10 x attenuation 9.5dB increases the decaying 20dB however angle while the deviation from the spindle sound pressure reduced, but at the same time as the deviation from the perspective of point to point and asymptotically the sound sources, thus it is not a sound pressure level attenuation and is increased. Actual sound engineering as well as two attenuation chosen to make their mutual compensation, making the sound radiation more evenly. Speaker's cone of radiation angle and its diameter D and the sound of the wavelength λ has a lot to do, the following table is a loudspeaker cone diameter D and sound wavelength than (D/λ) and radiation angle. Some of the information, as well as a 3 D/λ ratio and radiation angle. Figure 4 is a speaker cone of radiation angle and effective diameter and wavelength (λ/D), hence, we can conclude the following simple conclusion: 1, the speaker pointed to Tsz changes the frequency, the higher the frequency the shorter the wavelength, the paper Bowl effective diameter and wavelength ratio (D/λ) larger; speaker of the radiation angle is smaller, the more intense nature of it, the more narrow radiation. 2, speakers at various frequencies of radiation angle, the decision by the speaker of the tray, change cannot be arbitrary. 3, in the same frequency, the diameter of the large diameter of speakers than more small speaker directivity, because the ratio of D/λ, a smaller radiation angle beam becomes sharp and narrow, like table: how often the same 5000Hz to 12-inch speakers and a 4-inch speaker playback, 5000Hz d/λ ratio of 4.35 (12 inches), radiation angle only 180; 4-inch speakers 5000Hz d/λ ratio of 1.5, radiation angle is 500. This shows small-caliber speakers fit replay treble; General diameter speaker for playback in high, bass; large-caliber speakers fit to replay the bass and subwoofer. Whether it's broadcast, film and television recording and listening or theatre, Conference Hall, stadium sound reinforcement, we should consider this as possible.