The speaker is called the mouthpiece of the sound system, and the final re-interpretation of the sound source depends on this. It shows its important position in the sound. It is no wonder that many high-end speakers abroad cost hugely, and it is not uncommon for hundreds of thousands of people. The hot spots of fever come from this. In addition to the high-quality driver unit (speaker), the suitable cabinet structure and processing and processing technology are also of great significance. Since the speaker unit has been manufactured by the factory. Stereotype, the design and production of the cabinet has become the decisive stage affecting the performance of specific units. This article only summarizes the following points in terms of production materials and processes, according to the introduction of newspapers and publications and my own production practices. The main function of the speaker is to eliminate the acoustic short circuit, improve the sound pressure and uniformity of the bass, and improve the acoustic characteristics of the low frequency band of the speaker, but its intervention will also bring some negative effects, such as enhanced formant, medium and high frequency reflection. And diffraction, and so on, lead to bass sounding and high-pitched sound dyeing. Try to eliminate the negative effects and play the role of improving the bass, which is the basis of production.
Speaker material 1. High-quality wood such as mahogany, rosewood, mahogany, sandalwood and other precious hardwood, preferably seamless joint plate, the top material for the speaker, but the material is difficult, expensive, difficult to process, often used The best speaker is the second. It is the flower willow wood, jujube wood, eucalyptus, etc. It is better than the big one, the wood is even. The new material is damp and easy to deform, and it needs to be dried before it can be applied.
2. Medium density fiberboard This type of board is the most used, the cost is low, the material is easy to purchase, and the processing is convenient. However, the actual production is found to be inferior in strength, easy to produce acoustic dyeing, creping, and the material is fine and soft, and cannot be combined with wood screws. It can only be nailed with nails, which may be loosened under high sound pressure and has poor rigidity, which is not conducive to the rigidity of the box.
3. Medium-density particleboard, also known as pressure plate, has higher strength, lower cost and less processing. Many commercial speakers, including many Japanese set-up speakers, use this material, but some people report that the pressure is not true, including More air gaps, poor sound insulation. It is best to special treatment to improve sound insulation.
4. High-density fiberboard, particleboard and plywood have high strength, good sound insulation performance and easy to find materials. They are the preferred materials for amateur high-quality fever speakers, but the cost is slightly higher and the processing is not easy. Special tools are needed. Especially high-density particleboard , the hardness is very high, it is not easy to nail, I often twist the screw tip and do it in the production, use the hand drill to pre-spin the fine hole and then tighten the screw.
5. If the inorganic material is cast by concrete, it shall be formed by special process with stone plate (marble, concrete slab, granite slab, gypsum board, etc.), or simply use heavy earthenware pot as the box. It has small sound dyeing. Sound field stability and other advantages, often used by fever masters, just too heavy, mobile tuning is very inconvenient. And the box wall must be specially treated.
Six. Engineering plastics, polypropylene, reinforced modified epoxy resin, thick plexiglass plate and other high-density polymers (polymers) adhering to modern advanced technology materials technology, many European and American professional speaker manufacturers use this technology to create High-end, high-quality speakers, such as JBL MM series speakers are made of high-density plastic, and the famous JBLPROJECT K2 is made of high-quality throat with a few inches of plexiglass. It is difficult to achieve under amateur conditions.
7. Metal materials are mainly used for professional speakers and special occasions, such as stage speakers, mobile speakers, all-weather speakers for sports, all-weather mobile speakers for military use. Amateurs have high resonance frequency due to their high frequency. Handled and rarely used.
8. Paper materials are mostly used by enthusiasts who are eager to enter the burning tunnel and are economically strapped. There are also many experts who use this as a box and enhance the treatment with special processes, such as epoxy resin impregnation. If done properly, the effect is also good.
Production method 1. Plate combination This is the method used by most speakers including some of the best speakers. The process is mature, simple, and suitable for factory production.
2. Casting This method is most suitable for coagulation (Hong Kong called seamless sarcophagus) and high polymer.
3. The cavity method 1. Top-level fever speaker, the whole piece of expensive hardwood or sturdy stone is pulled out of the cavity as a box. It can be imagined that this method is very difficult and costly. Occasionally seen in European and American commemorative products.
2. The earthen speaker of the earthen gun family. It will be hollowed out on the ground, dry and moisture-proof, and then the upper panel and speaker unit. The cost is low, the sound quality is also very good, and the subwoofer replay is just right, but it can't move, it is all right. Article restrictions. High fever to this point, it really can be said to burn "home."
The high-fidelity speaker box in the production process is often in the high sound pressure of abrupt changes. It is easy to induce noise, resonance, and cause sound and dye, which affects the pure beauty of the music. Therefore, the production process is very important. “Reinforce vibration and avoid sound dyeing†For the production of the eight-character "guideline."
1. Widely and rationally use the reinforced ribs for the weak link in the speaker. The joints of the various faces in the box form a sufficient amount of glue, which is not too much, and sticks to the thick hard triangle wood or square stick, plus The wood screws are fastened, and the woofer has the highest sound pressure level on the back. It is easy to induce the box sound. On the back panel, a circular hard board is reinforced here. The material can use the remaining material under the panel opening, which is relatively narrow. The box body, because the sheet material is relatively large in aspect, the strength and rigidity are deteriorated, the resonance point becomes low, and the resonance frequency of the speaker or the box is asymptotic, and the sound dyeing danger is extremely great. Please apply a few hard square sticks asymmetrically. The purpose is to eliminate gap leakage, strengthen the rigidity of the box, destroy the resonance, avoid induced noise and stimulate the box vibration.
2. Add appropriate amount of sound absorbing materials in the box, such as ultra-fine glass wool, slag wool, fiber spray cotton, vacuum cotton, the second such as foam sponge, cotton wool, cotton paper, soft toilet paper, absorb sound energy, control the speaker Q value At the same time, reduce the vibration of the box. For the closed box, it is necessary to fill the whole box. For the inverted box, apply three fingers wide and wide sound-absorbing material to the front, back, left and right walls, and increase or decrease the amount during the monitoring to just suppress the resonance peak. For transmission line type (ie labyrinth), it is laid at the corner of the channel where the standing wave is easy to generate. For the horn type (mainly refers to the post-loading horn type) speaker structure, standing waves are easily generated behind the woofer and in the horn. Place a small amount of sound absorbing materials in the place. The amount of sound should be determined according to the actual listening evaluation.
3. The method of increasing the acoustic damping performance of the box wall is to make a layer of 1-2CM asphalt in each part of the box, and apply a layer of high-acoustic damping material (oil felt, rubber, etc.). The complicated but better method is to make Double wall, filled with dry dust and fine sand, or infiltrated the box with high sound damping material. This will block the transmission of sound energy to the box and greatly reduce the Q value of the box wall, even to reduce It is very effective to eliminate acoustic dyeing. The box made of inorganic materials must be processed.
4. Box Support Reinforcement This refers to the rigid support between the front and rear walls and/or the side walls by hardwood, perforated or round steel bars, so that the walls of the box are not excited by high sound pressure to produce annoying boxes. Acoustic dyeing, multi-hole plate has the function of Q-switching. Steel rod can be made of steel No. 40 or above, Φ45mm or more, and Φ8mm fixing screw holes are tapped at both ends. If necessary, if the cabinet is large, the welding flange can be added. It is fastened between the two walls to be supported by screws. According to some seniors, this method is particularly effective in eliminating the box sound caused by the poor strength of the sheet, so it is listed separately.
5. The fixing of the horn unit should adopt the fixing method from the outside to the inside to reduce the anterior cavity effect. The mounting hole is preferably used for countersinking to avoid the bulging of the basin frame and cause diffraction. The basin frame and the box are 5-10mm. The rubber mat is sealed and isolated to avoid short circuit and avoid the vibration of the basin frame to the panel radiation, which interferes with direct radiation.
6. Adopting special box shape and shape This is not to discuss the acoustic mode of the speaker, but to effectively prevent the standing wave. The generation of the standing wave will seriously affect the performance of the acoustic system. To eliminate the standing wave, destroy the box. Parallelism in the body is the key. For example, the TANNOY SIX series uses a hexagonal design. Many professional speakers use a fan design (JBL MM-SERIES, AC, etc.). The shape of the cabinet also has a greater impact on the radiation characteristics. Too many sharp corners can cause diffraction and interference, and a blunt surface transition angle can be used. The shape of the front panel affects the service angle and phase characteristics, and can be improved by specially designed panels, including curved design, stepped design, and Other special shapes. The front panel of JBL 4208 is computer-assisted analysis and design, and the surface of a reverse plane is used to effectively improve the phase characteristics of the near sound field. BOSE301 is introduced after the research of direct and reflected sound technology. Hi-Fi masterpiece, it adopts a unique shape design, cuts a bevel on the top of the subwoofer, and installs two tweeters for radiation in different directions, effectively creating a uniform sound field. It is said that listening to stereo is no longer just a "selfish" enjoyment when sitting in the emperor's position. It is said that a new type of speaker shaped like a big snail will soon be available as the new flagship of British B&W. So when designing the speaker, it should also Emancipate the mind, break the tradition, be bold, be diligent, and be good at thinking.
7. The strong sound absorption and strong acoustic damping material on the panel will be transmitted to the panel, and the direct sound radiation will be reflected on the panel. The vibration generated by the air stiffness in the box will also be reflected on the front panel. Panel radiation, superimposed with direct sound, interference, causing more peaks and troughs on the frequency characteristic curve, phase characteristics are degraded, especially under high audio, and the panel is attached with "heavy damping" material is an effective method to improve. Damping materials include high-density foamed foam, special felts, and factory-specific sound-absorbing sound-absorbing felts.
8. After completion, the speakers should be supported and “isolated†from the ground to avoid the sounds of puffiness, unstable sound field and poor transparency. Support methods include support frames, metal feet, hardwood feet, etc. Hard material test decided to contact the ground with a cone tip of 45 ° ~ 60 ° taper.
The crossover making crossover plays an important role in the speaker system. It is necessary to ensure that the high and low frequency signals are transmitted to the respective units without any interference, distortion, and intermodulation, and the frequency response curve does not cause a large Peaks and valleys, no large phase distortion. At present, LC power is frequently used. As for electronic frequency division, it is not discussed in this paper.
1. Under the amateur condition of the inductor, it is difficult to find the magnetic core that meets the requirements, let alone test the linearity, magnetic flux and other properties. Even under professional conditions, it is not easy to find the ideal core, so the core structure is difficult to care for. To be too harsh for enthusiasts. In order to reduce the additional resistance, we should try to use thicker high-quality enameled wire (anaerobic copper wire, large crystal copper wire, single crystal copper wire is better), preferably Φ1.0~1.2mm, And computer-aided optimization design, so that in the case of a certain amount of inductance, the resistance is the smallest, the resistance value should generally be less than one tenth of the horn impedance. Because the paramagnetic material will affect the inductance, the inductor should be as far as possible from the horn head, Fixing paramagnetic materials such as dowels and supporting steel bars, each frequency dividing component is fixed by epoxy glue to avoid increasing magnetic saturation distortion and causing drift of the frequency division point. The inductance coils are caused by space coupling. Mutual electromagnetic interference should be kept as far as possible, and placed perpendicular to each other with the magnetic axis. The high and low-frequency sound distribution networks are separately placed on a circuit board and away from each other. This is an excellent fever method.
2. Capacitor is preferred to have non-inductive polypropylene, polystyrene and other non-inductive film electrodeless capacitors. Avoid using electrodeless electrolytic capacitors, and it is not suitable to use extreme electrolysis reverse series. More than one small capacity capacitors are used in parallel. A large capacitor, its winding inductance is much smaller, the speed is much faster, has better high frequency performance and sound quality. The way to save without damaging the fever is to select only the signal path of the high and low woofer. The above components, while the bypass inductor, bypass capacitor slightly lower requirements, with ordinary electrodeless capacitors, thinner wire diameter inductance.
3. Wiring There are a variety of high-quality speaker cables on the market, which can be used as appropriate. The core wire is thicker, the number of shares is higher, and the copper content is higher. The copper crystal is longer and louder, such as the silver wire. Pay attention to counterfeit and counterfeit products. The method is better for bi-wire or tre-wire. Many magazines have introduced. Note that the lead does not affect the tightness of the cabinet.
The end of speech box production is a more complicated system engineering. It is an edge science technology between mechanical engineering, acoustics, psychology and ergonomics. It is both technology and art. The above measures complement each other and should be In the actual production process, according to the specific circumstances, symptomatic prescriptions, comprehensive application, will certainly be able to make more satisfactory works.
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