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General principles of car audio
General principles of car audio：
1, introduction
Now the speaker is according to structure the classification, such as closed box, inverted box, empty paper basin box (passive radiation box), the labyrinth box, secondary phase inverted box, the front horn box, after horn box, box type gun in a low voice, tube type with low gun, load, transmission line type, pipe type and so on is about more than 10 kinds of way, and each speaker shall have their own principles of interpretation, most explanation incomplete fully.We know that the set speaker intentions has two, one is because frequency in 1~200Hz following in a low voice no direction of, the diaphragm the front and back of the acoustic wave is reversed, depressed, low short circuit caused by, resulting in low frequency sound pressure drop and thus need sound barrier before and after sound wave; the second is the limited size of the frequency response of a single speaker, to expand the frequency response, need more than two speaker separation operation in divergent kind of band to achieve the height to be extended at both ends of the request. Avoid short circuit questions, but the energy of the sound wave is not used. To improve this shortcoming, we made clear more than 10 kinds of measures for the speaker, to avoid a depressed, low short circuit under the premise, full use of the radiated acoustic energy back, electroacoustic rotation power of progress, expand the low frequency echo. More than 10 kinds of speakers have their own interpretation of the operating principles, some of the more understanding, some of the more abstract interpretation, and even some one-sided misunderstanding. This planning manufacturing all kinds of speakers brought difficulty. Therefore, the author puts forward a new general speaker principle -- silencing and semi - anechoic principle. On the basis of fully understanding, can make good planning by analogy, wanton structure of speaker.
2, speaker classification
The traditional classification is the classification based on the box body structure, and according to the noise and semi - anechoic classification principle is according to the classification of a treatment method of acoustic radiation back, it will summarize all the moving coil loudspeaker is a together with the principle of noise and semi - anechoic principle. And is divided into two categories box, that is, the speaker and the speaker.
2.1 mute speaker
Silencing type sound box is in the box sound for mute processing and closed box that is typical of the fire box, in addition, big baffle box, back opening box, symmetry of a driving box, a horn box before were muffled sound box. After the silencing of two words, the working principle can generally know, silence is good or bad, is directly related to the quality of playback. Here can be divided into two bands back radiation, separation treatment. One is to listen to the resonant frequency band, and the other is to get rid of the full frequency band after the resonant frequency band, which is the non resonant frequency band.
For resonant frequency, did not participate in the sound absorption materials, acoustic energy is absorbed less, less energy is transferred to digest and resonance energies are larger, low unit at the resonant frequency of the resonant has not been too much inhibition, amplitude is still great, constitute a strong self inductance EMF and self inductance electromotive force (EMF) and the potential of the signal in electro acoustic two-way response (the author in another paper presents electroacoustic bidirectional response theory), the acoustic resonant frequency constitute maximum waveform distortion, which is part of the damage. Damage is when the electrical signal termination of inertia resulting in large amplitude with strong residual vibration, constitute a sound tailing variable length, the low-frequency become harass, rumbling sound. The rumble is more than a new trailing vibration, is not in the acoustic signal. Damage is intense amplitude high sound pressure, the wave distortion and big, will make low-end projection of the frequency response curve, destroying the balance of pressure. For speakers, the 3 way to reduce the damage is a useful way to add sound absorption. But the amount of sound absorption data is not the more the better, too much sound absorption materials, although cut down the first two damage, but also constitute a lack of strength in a low voice. This needs a compromise deal, how to grasp the amount of sound absorption materials, to what is the norm? Should be to reflect the resonance peak damping characteristics of the Q value for the specification, the speaker Q value is adjusted between 0.6~0.7. When the <0.6 value of Q is more than a long time, the damping is too low, and the low frequency is not clear. If the >0.7 value Q for a long time, the lack of damping, low frequency sound pressure is rising, but the transient characteristics of the variation, low frequency with the sound of the sound, the sound wave is not clear.
Q value of the impact of the elements have two points, one is the Q value of the unit before the bin, the speaker manufacturers planning to determine, the user usually can only choose not to adjust. Two is the variety and quantity of sound absorption material in the box. These two factors influence each other, the lack of a hand, another hand to give compensation available. But the compensation is limited, such as a lack of damping low unit, quality factor Q value is too large, is not able to after adding sound-absorbing materials to enable the work in the best case, can make the good only.
The resonant frequency of the loudspeaker will drift upward, the magnitude of the drift, the influence of the volume of the box and the sound absorption data. The larger the box volume, the more sound absorption data, the smaller the upward drift, and the contrary. So the silencer resonance frequency, by unit, tank volume and absorption data with resolution. The unit resonant frequency is low, the box volume is big, the sound absorption material is much, the resonant frequency is low. It is worth noting that the resonant frequency of the unit, which is the leading role of. If unit resonance frequency is high, you can't expect to through increased volume of silencing box to extend the low frequency echo, because by enhance the silencing box volume can only get cut upward drift, and not the speaker resonant skip the speaker itself resonant point downward extension (semi - anechoic can enough). Low frequency of a pair of speakers, it should be low frequency, sound pressure enough, no sound. And the frequency and sound pressure is difficult to take care of the most
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