Processing process in speaker production

RF cable can be customized for other specifications

In addition to the use of high-quality drive units (speakers), the production of high-quality fever speakers, the appropriate box structure and processing, processing technology is also of great significance. Since the speaker unit has been factory-set, the cabinet design and fabrication has become a decisive stage influencing the performance of a particular unit. This article only summarizes the following points in terms of production materials and processes, according to the introduction of newspapers and periodicals and my own production practices, in order to eat the vast number of people who are burning, and to learn from each other.

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 strengthening the formant, mid-high frequency reflection and diffraction, etc. , leading to bass sounding and high-pitched sounding. Trying to eliminate the negative effects and play the role of improving the bass is the foundation of production.

1 Production method

(1) sheet bonding

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) Cast molding

This method is most suitable for coagulation (Hong Kong called seamless sarcophagus) and high polymer.

(3) cavity method

a Top-grade fever speaker that takes a piece of expensive hardwood or sturdy stone out of the cavity as a box. It is conceivable that this method is very difficult and costly. Occasionally seen in European and American commemorative products.

b Earth speaker of the earth gun family. The ground will be hollowed out, dry and moisture-proof, and the upper panel and speaker unit will be installed. The cost is low, the sound quality is also very good, and the subwoofer replay is just right, but it can't be moved, and all the conditions are limited. At this point, the high fever has really burned to the "home."

2 production process

The high-fidelity speaker box is often in a high-pressure sound with a sharp change, which is easy to induce noise, resonance, and cause sound and dye, which affects the pure beauty of replaying music. Therefore, the production process is very important.

“Reinforce vibration and avoid sound dyeing” is the eight-character “guideline” of the production process.

(1) Reasonable use of reinforcing ribs

Used for weak links in the speaker. At the joint angle of each surface of the box, use a sufficient amount of glue, not too much, stick a thick hard triangle or square stick, and add wood screws and mosquito nails to fasten. 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 stuck on it. The material can use the residual material under the opening of the panel. For the relatively narrow box, the thickness of the sheet is relatively large, the strength and The rigidity is worse, the resonance point becomes lower, the resonance frequency of the speaker or the box is asymptotic, and the sound dyeing is extremely dangerous. Please apply a few hard square sticks asymmetrically. The move 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 material 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, while reducing box vibration. For a closed box, the entire box needs to be filled. For the inverted box, apply three fingers wide and wide sound absorption material on 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, a small amount of sound absorbing material is placed behind the woofer and in the horn where the standing wave is likely to be generated. The amount of it should be determined according to the actual listening evaluation.

(3) Increase the acoustic damping performance of the box wall

A simpler method is to pour a layer of 1-2CM of asphalt into each part of the box and apply a layer of high-acoustic damping material (oil felt, rubber, etc.). A more complex but more effective method is to make a double wall with dry dusting sand in the middle or infiltrate the box with a high acoustic damping material. This action blocks the transmission of sound energy to the tank and greatly reduces the Q value of the tank wall, which is very effective in reducing or even eliminating acoustic dyeing. The case made of inorganic materials must be subjected to this treatment.

(4) Box support reinforcement

Here, it refers to the strong support between the front and rear walls and/or the side walls by hardwood, porous wood or round steel bars, so that the wall of the box is not excited by high sound pressure to produce annoying sounding of the box. There is a role of Q adjustment. Steel rods 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 box is large), the welding flange can be added and screwed to the two walls to be supported. Between this, according to some seniors, this method is particularly effective in eliminating box sounds caused by poor sheet strength, so it is listed separately.

(5) Fixing the speaker unit

It is advisable to use an externally fixed method to reduce the anterior chamber effect. The mounting hole is preferably treated as a counterbore to prevent the basin frame from protruding and causing diffraction. The basin frame and the box are sealed and sealed with a 5-10mm rubber pad to avoid short circuit and avoid the vibration of the frame to the panel radiation and interfere with the direct radiation.

(6) Adopt special box shape and shape

This is not a discussion of the acoustics of the speakers, but an effective defense against standing waves. The generation of standing waves can seriously affect the performance of the acoustic system. In order to eliminate the standing wave, it is the key to destroy the parallelism inside the box. For example, TANNOYSIXseries uses a hexagonal body design. Many professional speakers use a fan design (JBLMM-SERIES, AC, etc.). The shape of the box also has a large impact on the radiation characteristics. Excessive, too sharp edges can cause diffraction and interference, and a more blunt surface transition angle can be used. The shape of the front panel affects the service angle and phase characteristics, and the specially designed panels can be improved, including curved surfaces, stepped designs, and other special shapes. The front panel of JBL4208 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 a Hi-Fi masterpiece launched after the research of direct and reflective sound technology. It adopts a unique shape design, cuts a bevel on the top of the subwoofer, and installs two tweeters for radiation in different directions. It effectively creates a uniform sound field. It is said that listening to stereo is no longer just a "selfish" enjoyment when sitting in the emperor. 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. Therefore, when designing speakers, you should also emancipate your mind, break the tradition, be bold, be diligent, and be good at thinking.

(7) Apply strong sound absorption and strong sound damping material on the panel

The residual vibration of the basin frame can 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. Any such kind of radiation through the panel will be superimposed and interfered with the direct sound, causing the frequency. More peaks and troughs appear on the characteristic curve, the phase characteristics are degraded, especially under high audio, and the "heavy damping" material on the panel is an effective method to improve. The heavy-duty damping materials include high-density foamed foam, special felts, and factory-specific audio-specific sound-absorbing felts.

(8) The speaker after completion should be supported

"Isolated" from the ground to avoid puffiness, unstable sound field, and poor transparency. Support methods include support frames, metal feet, hardwood feet, and the like. It can be widely used in different hard material tests, and the taper tip of the taper of 45° to 60° is in contact with the ground.

3 divider production

The frequency divider 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 large peaks and valleys. No large phase distortion. At present, LC power is frequently used. As for the electronic crossover, it is not discussed in this article.

(1) Inductance

Under the amateur conditions, it is difficult to find a suitable magnetic core, let alone test its 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 for the enthusiastic and overly demanding 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 adopt computer-aided optimization design.