The development trend of speaker technology

At present, there are more than 280 professional manufacturers engaged in the production of loudspeakers and sound boxes abroad (according to AUDIO data), and there are thousands of products produced. Speakers and speaker systems are used as audio playback terminals, and their quality will directly affect the sound quality of the entire audio system. Major foreign companies engaged in speaker production have invested a lot of effort to continuously develop new speaker products to meet the higher requirements of different use environments and different audio equipment. In recent years, with the development of digital audio technology, the requirements for speakers have become more stringent. In order to meet the requirements of technological development and meet the needs of consumers, well-qualified speaker companies from all over the world are committed to improving the performance of existing speakers, and researching and developing new materials, new processes and new design methods for speakers. The current status, characteristics and unique new technologies of loudspeakers and their system technologies of world-renowned large companies are introduced as follows:

1. The technical status of foreign speakers and speakers

1. Professional speakers

Mainly refers to speakers and sound boxes used in movies, stages, halls, stadiums and other occasions. In recent years, with the development of new materials, new technologies, new structures, and new processes, the application of stereo technology, digital technology, the popularity of DVD and MD, professional speakers and their systems have also made great developments, and new products have continued to emerge . JBL, EV, and BOSE companies in the United States; KEF and TONNY companies in the United Kingdom; and Panasonic, Pioneer, Mitsubishi, TOA, and YAMAHA companies in Japan have all launched various professional speakers and speaker systems in recent years. Their distinctive features are that they have high endurance power, above 200W; high efficiency, generally 98-100dB; and wide directivity.

In order to achieve the above characteristics, the world's highly qualified speaker manufacturers have crossed the sea, each showing their magical powers. The main methods adopted are as follows: First, the use of new magnetic materials and the use of new magnetic circuit design methods. For example, the SFG magnetic circuit design adopted by JBL company includes a new structure setting for magnetic flux balance, reducing the inductance of the driving source and heat conduction. The magnetic material used has a magnetic energy product of 3.6MGOe or more. This increases the capacity of the speaker to withstand the power, and the bass replay is strong and powerful. Second, the use of new materials, such as the use of aerospace titanium for the tweeter diaphragm. Because the E·P of titanium is superior to aluminum, it is suitable for manufacturing high-quality treble diaphragms. The tweeter using the titanium diaphragm has a larger high frequency extension and a substantial increase in power capacity. The woofer uses a laminated high-density composite paper cone. The voice coil adopts a flat wire. Due to the high space factor of the flat wire and the high utilization rate of the magnetic circuit gap, higher sensitivity can be obtained. The technology was invented by JBL, and other major companies followed suit. Thirdly, with the new model of horn, the exponential horn loudspeaker that has been used for a long time in professional sound reinforcement has been replaced by a new type of directional horn. The key technology of the equal-directional horn is that the horn adopts different shapes of side walls, from the simple linear and exponential type in the past to the complex and discontinuous functional type to achieve constant directivity. Fourth, extensive use of computer CAD, CAM and CAT technology, using modern technology to tap the potential of traditional speakers, so that professional speaker products keep improving. Representative products, such as JBL's MR professional speaker speaker series and SR professional speaker speaker series.

2. AV speaker speakers

Mainly refers to the loudspeaker speakers used in the sound system of home high-fidelity sound system, karaoke hall, dance hall and home theater. AV speakers have made great progress in the past few years, and new products continue to emerge. The world's major speaker companies have introduced various forms of AV speaker speakers. They not only have advanced technical performance, but also have practical modeling, high sensitivity, large dynamic range, wide playback frequency band and good transient response. There are two common two-way crossover speaker cabinets: an 8-inch or 6.5-inch mid-woofer plus a dome tweeter. Since a single speaker is used in the middle and low frequencies, the speaker unit is required to have a wide piston vibration range without split vibration to ensure ideal directivity and phase characteristics. According to the requirements of enthusiasts pursuing bass effect, various companies have successively developed dumbbell-type loudspeaker enclosures, using a dome tweeter between two 8-inch or 6.5-inch mid-woofers to enhance the bass. Three-way crossover loudspeaker box: Add a midrange unit on the basis of two-way crossover. The advantage is to make full use of the piston vibration frequency band of each unit, reduce distortion, and improve power tolerance. Another notable feature of AV speakers is that they have better anti-magnetic leakage performance. The magnetic circuit must have a magnetic shielding design to ensure that it does not affect the video image.

Nowadays, popular multi-dimensional stereo and home theater systems refer to the audiovisual effects of theaters in ordinary homes. Surround sound is a part of it, and it is a very important part. The popular surround sound on the market is roughly divided into two types, one is Dolby Pro Logic surround sound, which evolved from the early "four-channel"; the other is DSP surround sound, which was first developed by YAMAHA. DSP surround sound uses digital processing technology to simulate the sound effects of different spaces (such as a movie theater, concert hall, etc.). This requires the front, center, and rear indicator speakers to have balanced sound and ideal directivity. Engineers in the electroacoustic industry have made unremitting efforts to improve the performance indicators of AV speakers. Through system design, experimentation and simulation, they have continuously explored the mysteries of the AV speaker world, and ensured the objective parameters of the speakers on the basis of ensuring the sense of hearing. Occupy an important and necessary position. Representative products, such as JBL's home theater speaker system, include 7 speakers in total, including front main channel, center channel, surround channel and subwoofer. The front main channel uses 2 200mm woofers, 2 127mm midrange units, 1 titanium dome tweeter and horn tweeter. The horn tweeter is used in movie mode, and the titanium diaphragm dome tweeter is used when listening to music. The playback sound quality is very comprehensive. It uses a multi-channel sound equalizer and a 7-channel sound quality equalizer, and uses digital technology to create a magnificent theater sound effect in a smaller home space.

3. Subwoofer

In the past, in order to achieve true bass output, designers used as large a cone as possible. Such as KLIPSCH company’s 27-inch subwoofer; EV company’s 30-inch cone subwoofer, etc. In recent years, the booming home theater audio market has promoted the research and development of large-amplitude subwoofers. Representative products are: 18-inch subwoofer with radial neodymium magnetic system from AURA SOUND. By controlling the thickness of the top plate and using a 0.5-inch voice coil in a 2-inch long magnetic gap, a larger linear motion range can be obtained. PIONEER’s subwoofer has a unique innovation. From the outside, people may think that it has no overhangs. In fact, it sticks a structure similar to overhangs behind the diaphragm, allowing the diaphragm to work in a cylindrical frame. Longer piston movement. The cone of this subwoofer can move back and forth up to 2cm, and the 6-inch woofer can reach a sound pressure level of 100dB at 50Hz, which is difficult for traditional woofers to achieve. Representative products, such as KEF's AV1 active active subwoofer.

2. Main features and unique new technologies of loudspeakers from well-known foreign companies

1. JBL Company

The characteristics of the speaker are: high power, 200-300W; high sensitivity, greater sound pressure level above 110dB; good frequency response, flat frequency response and excellent transient characteristics.

Unique new technology:

(1) The magnetic pole core of the low frequency loudspeaker of the sound box is quite thick, the magnetic pole core is hollow, and the inserts formed by wire cutting are inlaid on it. This specially designed magnetic pole core can reduce the weight of the speaker, facilitate heat dissipation, and aim to improve the power capacity.

(2) As an advanced technology, the flat wire voice coil was invented by JBL. It was first used in woofers, and later tweeters were also commonly used, both with aluminum wire and copper wire. The flat wire has a high space factor and a high utilization rate of the magnetic air gap, which aims to improve the sensitivity. According to the test, in the same magnetic circuit, the flat wire voice coil can increase the sensitivity by about 1dB than the round wire voice coil.

(3) The titanium diaphragm dome-type unit is also the first success of JBL company. The Young's modulus of titanium material is superior to that of aluminum material. The high frequency upper limit of the high frequency loudspeaker using titanium film can be greatly expanded, and the power capacity can be greatly improved.

(4) The SFG symmetrical magnetic field magnetic circuit titanium diaphragm is a patented technology of JBL. This patented technology ensures that the FB value distribution on the magnetic gap is symmetrical and the upper and lower positions of the voice coil are equal. It includes a structure setting that balances the magnetic flux and reduces the inductance and heat conduction of the driving source. Effectively suppress low-frequency distortion, improve power tolerance and damping characteristics.

2. BOSE Company

The characteristics of the company's speakers are: actively using the reflected sound of the listening environment to improve and modify the radiation characteristics of the speakers, and develop a world-famous sound field speaker.

New technology of BOSE company:

(1) Direct/reflective speaker technology. BOSE's speakers use direct/reflection technology to restore the mixed sound reflected from the walls, ceiling and floor to the audience, and use the direct/reflection theory to express the level and location of the sound vividly. Representative products are 901, 701 and 501 series speakers.

(2) Sound air flow bass technology. This technology uses the airflow generated by the "A-coustic Mass" structure to couple three independent acoustic chambers to work, which can reduce the resonance of the bass unit diaphragm, reduce distortion, and provide a great dynamic range.

(3) Audio wave guide technology. This technology is the scientific research result of BOSE company after 14 years of research, and has applied for a patent. Its characteristic is to install a long zigzag waveguide in a very small chassis structure, thereby increasing the low-frequency volume and creating a huge stage space that breaks the limit of the small box volume.

(4) HOROFINE thin film technology. This thin film technology is made of bamboo pulp and wood pulp. It has excellent and balanced plasticity and rigidity. It can meet the three main indicators of converting electrical signals into high-quality sound waves: low density and high Young's modulus. With large attenuation index, it can reproduce bright, clear and very natural sound in the middle and high range.

3. AR company

The company is well known for creating air-cushioned speakers. This type of speaker uses acoustic suspension technology, which supports the woofer through spring-like air in a closed box to obtain deep and powerful bass. This kind of loudspeaker began to appear in the 1950s and is still in use today, and it has been enduring for a long time.

4. French FOCAL Group Company

The company is known for creating high-quality loudspeaker units, and also produces a variety of styles of loudspeakers, which sell well all over the world. Some group companies have advanced speaker manufacturing technology, and they have four internationally renowned important inventions.

(1) Invented a new design called "MVF" (Mechanical Vibration Elimination) system. The use of this system can overcome the shortcomings of traditional cone-type loudspeakers' mechanical oscillation, reduce the intensity of the cone-divided vibration, and ensure high-fidelity playback.

(2) In terms of diaphragm design, the patented Polkevlar cone is light in weight and strong in rigidity, which completely solves the problem of sound staining and has an accurate frequency response.

(3) Invented the Polyglass (polyethylene glass) processing cone, which makes the cone have high rigidity and excellent internal damping characteristics, so that the sound of the unit is smooth and natural, and the music playback is detailed and accurate.

(4) The newly-developed diamond diaphragm in the 1990s can replay gorgeous sound.

The speakers of this company are characterized by high sensitivity, and most of the products are above 90dB. The midrange and tweeter units are coaxially installed on the centerline of the panel to produce accurate sound and image.

5. Danish DALI Company

The company attaches great importance to the audiometry procedures of speakers, and is never based on objective test results alone. The company has an audiometry jury composed of people with rich practical experience and professional music literacy, who will make a subjective review of the sound quality of each new DALI product to ensure the unique style of DALI products.

The most notable features of DALI speakers are: the front panel is as narrow as possible to control the sound diffusion angle; the cabinet is very hard, with a surface absorption layer device, which can effectively eliminate resonance, stabilize the sound field, and make the stereo positioning sense very accurate. The units used by the speakers have been tested and paired by the computer.

6. Features of British speakers

TANNOY's coaxial loudspeakers are well-known in the world and successfully solved the problem of phase distortion; KEF's invented "UNI-Q" coaxial technology, which realizes the ideal of coaxial treble and bass sound at the same point, so that the stereo image is accurate; QUAD specializes in Electrostatic speakers have spared no effort to improve and develop them; the small speakers of Celestion and Rogers have a 2dB bulge in the test curve at 2000Hz. Some people believe that this small difference will definitely affect the tone, but the two companies’ The product is a representative product of the British small box, which may be the mystery of the British voice.

7. New flat speakers

British Verity Company and NCT Company successively announced in 1996 that they had successfully developed a novel ultra-thin flat panel loudspeaker, which was indeed a major breakthrough in loudspeaker production technology.

For this type of flat panel speaker, the thinnest is 3mm, and the thickest is no more than 25mm. The effective radiation area can be determined by design, ranging from 25cm2 to 100m2. Verity's NXT speakers use electromagnetic drivers, while NCT uses piezoelectric ceramic drivers. The vibration plate uses carbon fiber and paper materials, and the speaker is very light. The speaker has a wide frequency response range, large directivity angle, and good sound quality. This flat panel speaker does not require a cabinet and can be hung on the wall or in the ceiling like a picture. Experts predict that the application prospects of such ultra-thin flat panel speakers are promising, and they will become a new generation of speakers in the 21st century.

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