Talking about the production of overweight low, BASS SPEAKER
Keywords: talk about the production of overweight low soundbox
Ultra-heavy low soundbox, commonly known as subwoofer, is very important to create a shocking momentum effect. Most grades are in the form of five speakers with the subwoofer, and the subwoofer is essential. In fact, the design is standardized, the production is superb, and excellent subwoofer. Its effect is quite charming in the home theater system audio. Unfortunately, it is a pity that the price of the subwoofer in the market is unreasonable. The price of affordable people is difficult to accept, and the world is often unable to. However, good-handed audio and video enthusiasts "self-driving, full of food", based on this, this paper intends to introduce a simple introduction to the design principle of the low cannon for interest. In general, from the composition of the low cannon, the bass also is also divided into a source and passive two categories. The so-called active subwoofer refers to the subwoofer of the power amplifier, where the circuit part except for power. It is usually also available with audio frequency filtering (the audio frequency component above the bass is removed), and the phase adjustment is adjusted. Volume adjustment and other units; and passive subwoofer is not in general speakers, consisting of units and passive power divider, where the divider is a low pass filter. Make the reset frequency range only for overweight low. The following is to introduce the low-sound gun-large unit speaker and power amplification.
I. The design principle and classification of low-sounding hood boxes will be generally three categories, namely closed speakers, inverted speakers, and belt filtering speakers 1, conflict speakers, this speaker box It is completely enclosed, as in the general so-called closed box, see Figure 1.
The characteristics of the closed speaker are simple structure, and the transient response is better. That is, the sense of listening is deep, clear. Insufficient is, under the same volume, compared with other types of speakers, the low frequency sluggish frequency is higher than other speakers, so if you want to get lower low frequency downlihood, you usually require a larger cabinet volume. And select a large speaker unit with a diameter, and the efficiency of the speaker is less sensitive than other types of speakers. In terms of volume design, there is an engineering design data for reference. When the resonant frequency fs of the speaker unit is below 50 Hz, the volume volume can be greater than 1.4. When FS is greater than 50Hz, the volume volume can be greater than 2 liters. The closing of the box is often required to fill a large number of sound absorbers in the box. The material is mainly glass fiber, long fiber wool, and can improve the smoothness of the speaker, and achieve the effect of equivalent to increase the volume of the cabinet. Theory Up to 40%, practical can be calculated by equivalent increase by 15% -24%, which is equivalent to reducing the volume of the box. In addition, filling the sound absorbing cotton can also improve the efficiency of the speaker. The correct fill amount, the maximum can improve the efficiency of 15%, and the sound absorbing cotton usually needs to determine the amount of fill by repeated audition, with the sound is not turbid (quantity Less), dull (too much) is the principle, and other types of speakers are also true. For closing low cannons, the requirements for units are strictly strict relative to other types of speakers, where FS is expected to be less than 40 Hz, QTS should be 0.3-0.6, FS / QTS ≤ 50. In addition to this unit diameter is preferably greater than 20 cm, and it belongs to a long stroke. 2, inverted speakers are the largest type of speakers on the market, and the speakers are designed with inverted phases, the so-called bass reflective design, see Figure 2.
Inverted speakers, in units of resonant frequency fs are relatively small, so power withstand power, the resonance distortion is small, but below the resonant frequency, the amount of cone potential displacement is increased, and the resonance distortion increases, Under the same volume and unit conditions, the inverted speaker can obtain a lower rate of low frequencies in a closed box. In addition, theoretically inverting the efficiency of inverting speakers can be greater than approximately 3 dB. Of course, inverted speakers include the design, production of inverted pipes, and the difficulty of adjustment is greater than the closed box. The inverted speaker also needs to fill the right amount of sound absorbing cotton, usually less than the closing box. On the unit selection, FS is good at low dry 45Hz, the QTS should be less than 0.5, and the FS / QTS value should be around 100 or so, the cell caliber should be greater than 17cm, in order to obtain a larger sound pressure power, the same as the closed box Yito, a unit of long stroke design is preferred. 3, the band-pass filter speaker This speaker is relatively rare, see Figure 3, Figure 4, can be seen from the figure, it is developing on the basis of the closed box and inverted speakers. Effect of both closed boxes Traces, there are also features of inverted speakers, in which the speakers shown in Figure 3 are also called a four-stage tape speaker, and the speakers shown in Figure 4 can be referred to as a six-order tape speaker.
A, the fourth-order band-through speaker adds an opening chamber in the closed chamber, one of which works in the closed box, and the other is in the inverting mode, so this speaker has both the advantages of closed boxes, also The characteristics of inverted speakers are characterized by a purely closed box. The low-frequency lacex frequency is similar to inverted speakers, and the lower slurry frequency can be obtained with a small caliber unit. In addition, its band pass frequency can be adjusted, so the divider can be simplified because the speaker itself is equivalent to the natural divider. On the unit selection, in principle, it is similar to the closing, but since the efficiency is slightly higher than the closed box, a smaller diameter, short stroke unit can be used in a small amount of the pot. B, the six-order band-through speaker has increased an opening chamber in the closed part of the four-stage tape speaker, that is, two open cavities, one of which is at a lower frequency, and the other is working in Higher frequency, the two synthesis has a frequency response having a wide bandwidth, compared to the above-mentioned four-order band, the adjustability of the bandwidth is more flexible, and the cells can be obtained by smaller caliber, more deeper The bass effect, at the same time, the cone pelvic displacement is smaller, and the resonance distortion is lower. On the unit selection, it is basically similar to the inverted speaker, but QTS is better than about 0.4, and the cell caliber has no strict requirements. If you want to get high acoustic pressure, low distortion output, the cell caliber is of course as much as possible Some are better. Due to the airflow of the inverted hole of the band-type speaker, the sound pressure is usually large, especially when the large dynamic, ultra-low frequency signal,, whether it is a fourth-order band speaker or a sixth-order tape speaker Inside the possibility, inverted pipes should be as big as possible to avoid airflow in operation. In the box design, the value of its volume is not based on the theory, especially the commodity box, mainly with the aesthetics, and the electroacoustic indicators reverted to each other. The adjustment of cotton can achieve the best level, of course, the closer volume is, the more the engineering calculation value, the more performance, the better the best level. In addition, in the production of the box, the internal reinforcing thus does not be ignored, and some to reinforce the resonance of reducing the speaker at the middle of the box seam and the middle of the large plate, so the body weight is always good.
Second, the constituent subwoofer is widely used in home theater system, which is the overweight bass signal in the film audio decoding process, whether in simulating Dolby, today's very popular digital surround system, Since there is an overweight bass signal, it is inevitably to play a special speaker. In terms of the composition of the low-sound gun circuit, it is generally composed of a pre-premium amplification, low pass filter, phase adjustment, power amplification, protection, and power supply, etc., in its role, pre-magnification is further overweight signal output by AV amplifier output Zoom in to drive the amplitude of the power output, because the overweight bass signal voltages provided by each grade AV amplifier are different, generally from 0.3-1 volts, so the pre-level amplification is necessary, the front-level circuit has An important role is the meaning of isolation buffering, because the overweight bass signals of each grade amplifier output are different, and some manufacturers are stolen, causing their output internal resistance, if they directly drive the subwoofer's power amplification unit It is possible to have a very bad effect; low-pass filtering is a relatively important unit in the subwoofer, which is to further filter the signals above the hypowas of the overwhelming signal of the power amplifier output, generally designed 80 -180Hz (Many high-end products are designed to be continuously adjustable), if they belong to a fixed frequency filter, the value is approximately at around 110-150Hz, and the low speaker is easy to produce a mixed drop, too high. It is easy to mix into the human ear (the super bass signal used for each grade AV amplifier output is inverse or the positive phase is not uniform, and thus the phase adjustment is based on the system connection when placed in the subwoofer. The subwoofer is in phase or inversely used, and it is essential, it is generally indispensable; the power amplifier unit does not have to be more than Luo Wei, it is the core of the source and low cannon, and the same, to protect the prevention of subwoofer safety work and exception When protecting the equipment is not damaged or enlarged, the protection circuit is generally necessary; the power supply is the power of the various circuit units, which is a basic component. It is necessary to supplement that some subwoofers have also designed power automatic control functions to automatically turn off the main power of the low cannon when there is no signal. This article provides a relatively complete overweight bass front-level signal processing part circuit, wherein the first stage is the signal amplification, which can adjust the magnification of the magnification, the second level is 50 Hz lower bass, which is a general low sound. If the gun circuit is not, the third stage is the frequency adjustable low-pass filter, the adjustment range is 80Hz-200 Hz, the fourth stage is the isolation scoring level, the fifth stage is 0-180 degrees continuous adjustment circuit. This is also generally low tone The function units of the gun are very characteristic, and the last level is also separated by the isolation scales, and the end is the volume adjustment potentiometer. Production party, the three double operations can be used in general 4558, and the power supply is ± 12-18V. Since the current is small, the power amplifier power supply can be obtained by resistance to the resistance to simplify the difficulty of design and production. For this circuit, it can be appropriately deleted as needed.
As for power amplification and protection, there is no difference between the power supply part circuit and the general amplifier. In order to save the space, it is used for subwoofer work and ultra-low frequency band, which is very power amplifier, and requires power to provide sufficient power output. Depending on the efficiency of the speaker, the output power is generally required to be more than 80W. Similarly, the power supply power reserve is also necessary. Otherwise, the distortion of the power amplifier output is increased and the output power is restricted, and the output power is restricted, and the effect of the low cannon is affected. Separate components or power integrated blocks, it should be possible, one is no doubt, for subwoofer, the larger the output power of the transformer and power amplification, the better. It is necessary to add that the speaker makes it seems simple, but it is necessary to make an effect, and the sound of the sound is really not easy. It is more difficult to spare, if the unit parameters provided by the manufacturer and provide a reference book design guide, the production of speakers is relatively easy to make speakers under amateur conditions, and the subwoofer is even more such. Of course, this does not affect some senior audio people with a spirit of repeated trial, debugging, and amazing listening to produce an outstanding speaker.
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