Popular Science, How Does The Speaker Sound?

- Jan 09, 2020-

"Speaker" is also commonly known as "horn". At present, human technology is used to convert electrical energy into sound waves. The most mainstream technology is the "electromagnetic" method. At present, speakers on the market are mainly designed and manufactured using electromagnetic principles.

The complete speaker will consist of several parts: speaker unit, crossover network, and speaker. We will discuss them in different categories. The first is the speaker unit. Basically, the working principle of the microphone is reversed. Electrical signals are input to the coil of the voice coil in the magnetic system. The coil changes magnetically with the signal, and the voice coil is driven in the magnetic system Wave motion of sound. The voice coil then pushes the diaphragm or cone of the horn unit to push the air to generate sound waves, and the sound is thus emitted.

It is not difficult to say, but it is another thing to make the electrical signal sound as low as possible, such as the original waveform and response. The audio range exceeds ten octaves from low frequency (20Hz) to high frequency (18kHz). If a single speaker unit can cover this audio range, the volume will be limited by the structure. But now the full-range monomer technology is mature and developed, there are already many full-range monomers on the market with good performance.


Of course, to build a loudspeaker system that can emit large volumes and high bandwidths, different sound ranges need to be assigned to monomers with different characteristics, such as low frequency (below 300Hz) for bass monomers and intermediate frequency (300Hz-2500Hz) for midrange. Monophonic, high-frequency domain (above 2500Hz) are separately pronounced for treble monomers, integrated into a complete range. The low frequency requires the largest diaphragm / sound cone because it needs to push a large amount of air. The middle range requires less air, so the diameter and size of the cone are smaller and lighter. The high range only needs to push the least amount of air. Air, so the tweeter is also the lightest and smallest diaphragm.

Basically, the larger the diameter of the single cone / diaphragm, the heavier the mass, the more air it can push, but it also has greater inertia so the reaction speed will decrease, so it is suitable for lower frequencies; otherwise The smaller the diameter of the diaphragm, the lighter the weight, the faster the response speed and the higher the frequency, but the relative amount of air that can be pushed is limited. This is why the speakers with a small volume on the market will be equipped with multiple audio channels and multiple units to integrate pronunciation.

Of course, in this case, the electrical signal of the amplifier must be divided into high and low channels or even middle channels, which is the so-called "frequency division". Generally speaking, there are two ways to divide the speaker system. The most mainstream way is to use a passive crossover network to divide the signal of the amplifier into sound channels with different frequency ranges. The passive crossover network is a "filter" composed of passive inductors, capacitors, and resistors. It filters out the frequency bands outside the range of the sound path, and only the required frequency bands can pass. Therefore, the speaker is provided with several sound paths, and there will be several sets of filter networks to form a crossover network, which respectively drive the units responsible for different sound ranges.

The other method is "electronic crossover", which is sent from the signal to the electronic crossover when the signal is still in the previous stage. In general, the frequency division effect is better than the passive frequency division network. However, the different sound paths produced by frequency division require different amplifiers to promote the individual sound paths. Therefore, the cost of the speaker system will be greatly increased; usually, electronic crossovers are used by relatively large speaker systems.

In the end, these monomers with different sound paths need to be installed into a complete speaker system. However, further consideration is needed. The monomers vibrate back and forth to push the air to make sounds. If it is not further processed, it will have the effect of canceling each other out in the listening space. Therefore, it is necessary to "box" the "back wave" emitted from the rear of the monomer for further processing. Generally speaking, each cell will have an independent space to handle the back wave. If the volume of the middle and treble is small, the sealed back cavity will be pre-processed when the cell leaves the factory.

Therefore, the loudspeaker is mainly designed for some larger midrange and bass units. At present, there are two mainstream methods of speaker speaker design: closed and open. The open mainstream is bass reflex, that is, the volume of the bass chamber of the speaker and the diameter and length of the reflection duct are calculated. Tuned to produce a larger (moderate) amount of low frequency performance. However, the volume of the closed speaker must still be calculated by taking into account the characteristics of the individual, so that the low frequency can be extended to the lowest frequency.

However, the open speakers are not only designed for bass reflex, but also many methods such as Isobarik form with two single-cell multi-chambers or transmission lines (separating the interior of the speakers into long ducts to extend low-frequency frequencies). There are also many designs on the material and structure of the speaker to strengthen its structure to avoid resonance and affect the sound quality. The most mainstream material is the so-called "medium-density fiberboard" (MDF). This kind of material has many advantages such as reasonable price, easy processing, and ideal results. characteristic. Of course, there are speaker manufacturers who use metal or special materials to design / construct speakers to obtain better characteristics and effects.

The above are the constituent elements of a typical speaker. Of course, there are other different designs that will deviate from the above. For example, the "plasma / ion tweeter" type uses air to drive air; the "electrostatic speaker" uses electrodes / electric fields to drive The film is used to promote the air sound, there is no speaker structure at all. There are indeed many other ways to turn electrical energy into acoustic energy, but the most mature and mainstream technology is still the traditional single unit based on the electromagnetic system and the traditional speaker integrated with the speaker structure.