"Longquan" audio technology "
Many enthusiasts generally use 6.5 ~ 8-inch bass unit speakers. These speakers are low, and the bass sounds, but the energy and extension capacity are insufficient. It is well known that bass is the basis of music signals. It has largely affected the atmosphere of listening, and the low signal sound will be light and not true. In the formal home theater play, the overweight low box is a very important one. If there is less heavy bass, it is completely lost, which means that it is not true. Therefore, the author suggests that if there is condition, or choose a large-scale fall box to get a richer low frequency response, and the home theater should take into account the overweight low. Of course, if the original system has no rich low-frequency effect, you can also add a high quality overweight low oscillator to improve the renovation. However, a little overweight low voice box is priced. Since we have the ability to design a bookcase or floor box, can we do a better overweight? The answer is yes, interested The reader may wish to follow me.
The concept of ideal overweight low speakers is before making, what we deal with "a good overweight low low voice box" has a basic concept. The author believes that there are several aspects that measure the quality of overweight low yinkers. 1. Good overweight low speaker must be an active amplification so-called "source zoom" is built-in amplifier, and passive ultra-low speaker is no built-in power, and there is only passive frequency divider in the box, and the main speaker is shared or Also equipped. The passive ultra-low soundbox is used to determine the volume using the quantity control of the pre-stage. If the sensitivity or volume and the main speaker are not average, it will trigger a mess, the frequency is uneven, and the sound image is not equal. At this time, the super-low soundbox cannot solve this problem, which is difficult to improve. Plus the vibration quality of the ultra-low large diameter unit is definitely greater than the main speaker unit, so the sound speed is slow, and the effect is often turbid after adding such an overweight low voice box. Active ultra-low sound box is designed for bass replay. Its work feature is that the signal is directly forwarded with the predecessor of the source. The frequency of 100 Hz or less is amplified by a dedicated bass amplifier and drives the ultra-low soundbox. The frequency of 100 Hz or more is sent to the amplifier after crossing, and it is broadcasted by the main speaker. At this time, there is a separate volume control to control the proportion of ultra-low tone volume and main speaker on volume. Regular addition ultra-low speaker is ultra-low tone to operate below the cross-frequency frequency (for example, 100 Hz or 120 Hz), while the main speaker operates above the cross-division frequency, but such a crossover is set after the signal source is output. Before the primary channel, therefore, some advanced ultra-low speakers have a pair of left and right channel output terminals, but many people in daily use are directly rejected from the predecessor to the ultra-low speaker. From this point of view, the unit and internal magnetic circuit structure used by the source ultra-low speaker, the dedicated low-frequency lifting technique, and the divided amplifier, the boxes, etc. are served for low frequency reproduction. Therefore, the performance of the active ultra-low soundbox is not a self-passage. 2. The ultra-low frequency is sufficient, and the function to extend enough low and low sound speakers is to make up for the low frequency of the main sound speaker. 3. Ultra-bass units must be able to withstand high power and become well known, the larger the area, the deeper the diaphragm low frequency, and in order to achieve sufficient energy, most ultra-low tone units are 10 inches, and the unit vibration The larger the membrane, the relative quality increases, and the movement of the unit is not easy to control, and a larger control energy is required to be substantially input power. Otherwise, the moving movement of the diaphragm can not make the line will make the sound blur, if the speed of the unit reaction does not keep the speed of music, it will cause the distortion of the low frequency band, so that the sound is unclear, and it will make the low frequency becomes weak and not enough. force. 4. To have a well-designed and sturdy box structure ultra-low sound is the most serious frequency band in the speaker play, but the low frequency band is actually hidden in many details and texture, like the low frequency of the bass cello and the organs, no fire The blind "sense of blind" high ", excellent performance, excellent performance, can easily listen to a variety of clever changes such as sound, details, and tone, and the ultra-low sound of the reaction can reproduce the impact of aggregation and effectively improve the analysis. In line with, the high frequency band is good. The long-width proportion of the box and whether there will be directly affected the detail of ultra-low, analyzable, speed, transient reactions, etc., can't be allowed to leave.
The design and production of the selection of materials will be the effect of comparable quality commodity machines through careful selection, well-designed production. First we choose the bass unit is a Willow Hi-FireSearch 12-inch W12 bass unit (Figure 1). It is characterized by high loss, high smooth, ultra-thin, fatigue rubber folding rings and Germany KEVLAR reinforced paper base composite membrane, with high heat-dissipating coating, no vort-loss loss, high load power 76 mm voice coil and High temperature SV lines and integrated high-density aluminum basins, its symmetrical magnetic field (SMD) drive system reduces the mutual modulation of voice coil inductance and back electromotive force, plus ultra-long stroke linear displacement design, so that it has a large power, FO (resonant frequency) and QTS (quality factor, total Q value) is low, transient, low frequency response, bass fever, high-definition and analytical force, large dynamics, low disrespect, and good advantages, it is very suitable for Source ultra-low sound. Several main related parameters of the W12 bass unit are: rated impedance 8Ω; resonant frequency (fo) 28 Hz; rated power 150 w (maximum 300W); sensitivity (2.83V, 1M) 90 dB; total Q value 0.42; vibration quality 89.7 g; Equipment (VAS) 156 L. Figure 2 is a structural dimension diagram. Be
After the selected unit, it should be considered to push the power size of this bass unit. In order to better control the movement of the bass unit, the author believes that the power of the power amplifier is not less than the 150 W rated power of the bass unit, but should not be greater than its maximum 300W. Input power, so the power amplifier output power should be around 200 W (8Ω). For general dozens of square meters, if the design is reasonable, this power is sufficient. The power amplifier for overweight low-sound boxes must not only have big driving force, but also its transient distortion is small, and the reaction speed is fast. The constant current amplifier driven here is to feed back the current sampling of the speaker voice circle to the actual amplifier input, so that the amplifier is driven in a fixed current method, so it is well solved the amplifier nonlinear distortion or transient The problem that distortion cannot be taken into account. There are many benefits to using constant current power driver. First, the current to the speaker voice circle is not affected by the speaker impedance, and thus simplifies protection, improve reliability; second is the feedback sampling voltage and flowing through the speaker voice circle Configure linear relationship, there is no phase difference, reducing the transient distortion inside the amplifier, the transient distortion indicator of the system depends on the transient characteristics of the speaker; it is the load of the power amplifier drive impedance with the output load characteristics will increase The intensity and analytical force of the sound, the reaction speed is also fast. Figure 3 is an active servo power amplifier for overweight low speakers. It is specifically designed according to the relevant parameters of the W12 bass unit. The line can output RMS power of 200 W, which uses negative feedback constant current designs for the upper and lower symmetry. This line is characterized by negative feedback to the emitter of the input stage transistor, and the respective bias circuits are combined into independent. The upper and lower symmetrical lines, the advantage is that the preamplifier is not easy to mix noise, and it is highly signal-to-noise ratio. The servo equilibrium phase, the design feature of the volume control line is the input from the source or the pre-stage output to the input terminal of the operation, the switches K1 and IC1B are used to control the signal of the positive and reverse phase, make it The main speaker has a more correct phase match. The line consisting of trialiographic switches K2 and IC1C is about 40 Hz, 55 Hz, 75 Hz, 100 Hz, a total of 4 low frequency input cutoff points consisting with a Badworth three-order low-pass filter.
Figure 3 Active Servo Power Amplifier for Ultra Low Low Sound Box Figure 4 is a power supply diagram for active servo power amplifiers. Both enthusiasts know that good amplifiers are not less than lines, in order to achieve a better sound, the machine uses a R-type high-quality transformer, and the magnetic and efficiency of R-type transformers is more common than common ring. Type or EI type transformer is good, low temperature rise, and placed in a relatively complex overweight low low sluggery in the use environment. It is significantly better than the ring or EI transformer.
The front and rear processing lines of the machine have their own independent power supply. The windings are separated. Among them, the power supply of the control line is used to output the power supply of the positive and negative 15V after the three-terminal regulation processing to IC1 and IC2, and the post-level amplifier is in order to reduce the power supply. Resistance, with 4 pairs of medium-capacity filter capacitors in parallel to obtain a faster reaction speed. In order to further reduce the mutual interference of the inner magnetic field, the entire active servo power amplifier is mounted in a 30 cm × 35 cm × 9.5 cm thick aluminum metal chassis, wherein the heat sink is an outer table mounted in the casing to facilitate heat dissipation. After obtaining the volume of the active servo power amplifier, we can easily find the lumen volume of the overweight low speaker. From several major correlation parameters of the W12 bass unit, the unit is more suitable for the inverted phase box, in order to obtain a low frequency response of relative flat rather than rendering, there is a relatively high transient response and a good low frequency extended, in the design case The SC4 response design is used. The SC4 response design is a better choice in inverted phase box design. Its feature is that the box is relatively large, but it has a low tuning frequency and relatively outstanding transient response and a lower distortion output characteristics, possibly Some readers ask why not use a better SBB4 response design? SBB4 is of course better, but we consider the sound quality of the two designs and the size of the cabinet, it is considered that the SC4 response is sufficient to meet high-level listening requirements. The inverted box with SC4 responded is good, but it requires a lower Q value in the bass unit, and the total Q value of the W12 bass unit is 0.42, and the basic attachment is required. The overweight bass is designed in accordance with the table, Table 1 contains the low Q value SC4 design data from 0.37 to 0.44, and the reader can also use this data when designing the SC4 in which the Q value is designed. Be
Based on Table 1, we will soon find the inner air volume of the overweight low speaker. Ask the box body air volume Vb: Vb = VAS ÷ α = 156 ÷ 0.9113 = 171.2 (L) Qihard frequency: fb = (fH ÷ fo) × fo = 1 × 28 = 28 (Hz) promise's low frequency Deceased frequency f3: f3 = (f3 ÷ fo) × fO = 0.937 × 28 = 26 (Hz) find down the tube length L: LV = 2350dv2 ÷ (FB2 × VB) -0.73DV where DV is the opening diameter of inverted pipe In order to get a good linear, this is 100mm here, calculated, LV ≈ 102.1 mm. According to the value of the volume formula, the value obtained is net capacity. When the actual calculation is calculated, it is necessary to remember the volume of the built-in amplifier (about 4 liters) and the volume of the speaker (about 4 liters), while the volume of the reinforced support can be provided. At about 9 liters, so, the final volume V = 171.2 + 10 + 9 + 4 = 194.2 L is actually calculated in 195. when actually produced. The inside of the box is high, wide, and the deep size is closely related to the sound quality. If the size is not appropriate, it may cause two or even three axial vibration frequencies to overlap, produce difficult to eliminate stand / wave interference, so that the sound is added . In order to reduce unnecessary influence, the high, wide, deep proportion of this chamber is 1.3: 1: 1.2. Calculated, the interior of the box is high, wide, and the depth size is 65 cm, 50 cm, 60 cm, respectively. The casing is fabricated with a 25 mm thick medium density fiberboard (MDF) to improve the rigidity of the casing, and there is a support plate inside the casing, and the front crucial plate is bonded to a medium-thickness fiberboard (MDF) bonded by two 25 mm thickness. Get up to reduce the exhaust of the tank resonance to get a clearer sound. Figure 5 is a production dimension diagram of the speaker. Please pay attention to the processing of the boss line contact surface when it is made. The combined surface should be coated with the wood gel, and tighten the wood screw to ensure that the engagement is closely revealed. . To balance the weight of the front and rear barrier, the active servo power amplifier is provided in the backcrossboard, the heat sink is a show design. As can be seen from the backcrut board of the box, the inverting hole is behind, that is, the box is not too close to the rear wall. Be
The placement method of the sound absorbing material in the general speaker has two types of paste and filling. The inverted speaker is often pasted, the amount of sound absorbing material of the box is a 5 cm thickness of the cotton wrapped in the box wall. Mine pad. If it feels too much low frequency energy, the sound absorbing material can be properly thickened. In this way, the total Q value (QTS) of the speaker decreases, which can change the low frequency thickness, making the bass clearer and improve the transient reaction speed. For ultra-low speakers to get a clear high resolution bass, the box should be used for metal pin, preferably with copper foot cone.
In use, if the low frequency input cutoff is too high, it is overlapping with the low frequency band of the main speaker. The low frequency is turbid to drag in some frequency bands, which will affect the speed and clarity of the low frequency. Conversely, when the low frequency input cutoff is too low, the low frequency will also have a phenomenon, which makes people feel that the main speaker and the ultra-low speaker are "each work". Therefore, selecting a reasonable low-frequency input cutout point to make the main speaker and ultra-low speakers to achieve smooth low-frequency transitions, and low frequencies will increase, but they will not feel too abrupt, rendered, so that the overall momentum is integrated. The general adjustment principle is that the lower -3 dB low frequency lower limit is 6O Hz, which is suitable for 55 Hz low-frequency input cut-off points, or can be roughly prepared. If the bass unit of the main speaker is 4 ~ 5 inches, select 75 Hz low frequency input cutout points; such as a bass unit is 6 to 7 inches, select 55 Hz low frequency input cutout or lower gear. The volume adjustment of the ultra-low speaker should not be transferred (preferably not more than 10 o'clock), prevent ultra-low sounds from being smashed and reducing distortion. When the phase is adjusted, first put a low-frequency plus music, then set the phase at 0 ° and 180 °, compare the amount of low frequency in this time, with a full sound, clear voice, and the agglomerator is better. When the adjustment is good, the ultra-low speaker has been integrated into the entire system, you will feel its power. It takes about 2,500 yuan to be produced like this, but its sound is comparable to a cost box that is quite doubled, and it is real. Friends who need it, don't worry about it. "
Our other product:
