[Home Theater Network HDAV.COM.CN] The band speaker is a kind of electric speaker, but unlike the vibration system of the cone speaker, it consists of a voice coil and a diaphragm, but a "belt" is used. A conductive tape is placed in the magnetic field generated by the magnetic gap, and the belt generates electric power under the magnetic field by the alternating current to cause the belt to vibrate and radiate the sound wave. The straps here are made of aluminum foil, also known as aluminum ribbon speakers. The principle of the belt tweeter: an ultra-thin aluminum strip is used as both the diaphragm and the voice coil (the aluminum strip is both a conductor and a vibrating body), placed in the magnetic gap, and when the current passes, the aluminum strip is driven to vibrate and radiate. The aluminum belt treble has good transient characteristics, fast response speed, wide frequency upper limit, small distortion, rich overtones, etc. The most prominent advantage of the aluminum belt treble is the ultra-high frequency band, which is further for the high frequency extension and resolution. Play and accurately control. Because the production of aluminum ribbon tweeter has a lot of scientific and technological content, there are not many countries that can produce such speakers internationally, even if the manufacturer with this technology has higher production cost, resulting in its price is not Philippine, coupled with technical problems such as low magnetic efficiency, has not yet been fundamentally solved, making it impossible to truly gain popularity. Ribbon tweeter (band tweeter), the principle is to apply audio current to the conductive film placed in a uniform magnetic field, the magnetic field generated by the current and the uniform magnetic field mutually repel each other, attracting, and the film is subjected to vibration and sound. The main advantage of the band speaker is that the diaphragm is light and has a large area. It is generally used in the playback of the high-pitched part, and can obtain a high-pitched sound with extremely high definition, extremely fast transient response and small phase distortion. A speaker that vibrates the sound with an aluminum strip placed in a magnetic field as the audio current changes. The structure is composed of strip magnets to form the magnetic gap of the two poles of N and S. In the magnetic gap, an aluminum sheet is arranged in the magnetic gap to make a vibrating body. When the alternating current is fed into the magnetic strip, the magnetic field lines are in the magnetic field. Under the action, the aluminum strip vibrates with the change of the audio current, thus completing the process of converting the audio signal into sound. Since the aluminum sheet is very thin, the quality is very small, and the weight is extremely light, the number of vibrations per second is very high, that is, the sound of a very high frequency can be reproduced (up to 22 kHz), so the aluminum strip The speaker has excellent high-frequency characteristics and pure tone, making it suitable for tweeters. In recent years, due to the widespread use of ferromagnetic materials such as neodymium magnets, the diaphragm material has also been improved from aluminum to composite materials (mostly Kapton substrates, printed pure aluminum conductors), which greatly improved the performance of the band speaker, and the internal resistance increased to 4- 8 ohms, no need to use transformer to convert impedance, power can be more than 10W, efficiency is also increased to 90 decibels or more, and can be well matched with commonly used woofer. First, the characteristics of the aluminum belt speaker: Some people say that the aluminum belt speaker is a high replay frequency, > 20khz, the Earth people basically can not hear, so it is purely a gimmick. Let's not say whether it is a gimmick, in order to further clarify the characteristics of the aluminum ribbon speaker, it can be compared with the dome speaker, because these two speakers are mainly used for high frequency playback. I am not saying that the aluminum belt speaker is definitely better than the dome speaker. In terms of sound color, I always think that "the best aluminum belt speaker is like the advanced dome; the best dome is like the aluminum belt speaker" 1. Low diaphragm quality: The vibration quality of the aluminum belt speaker is very low, generally only 30mg-40mg, and the dome diaphragm is about 350mg, the difference between the two is 10 times. Therefore, the aluminum belt speaker diaphragm is “better controlâ€. Compared with the dome speaker, the corresponding difference between the two pulses is obvious. After the pulse signal disappears, the aluminum belt speaker quickly “closesâ€, and the dome speaker has large inertia due to mass. "Yu Zhen" is more obvious. This is very important when replaying music works. Popularly speaking, it is fast and can reproduce the content of the signal that is less than fleeting, that is, the details. In addition, we know that the tone (or texture) of the instrument is determined by the harmonic component. The spectrum of the harmonics is often dense. The frequency of each frequency is different. It is very necessary to have a very fast vibration system to "reproduce this complex spectrum." ", replay the most realistic texture! So the aluminum belt speaker has a place to show your skills. 2. The BL value is low: compared with the dome top treble, the aluminum belt speaker is located between the magnetic gaps due to the vibrating parts, so the magnetic gap is large (about equal to the diaphragm width), the magnetic flux density is not high, and the length of the aluminum strip is generally It is relatively short, and eventually the BL is naturally smaller and the driving force obtained is limited. This is one of the disadvantages of the general aluminum belt speaker. 3, the resistance can be neglected: for the dome and the vertebra speaker, the resistance ni is an important position and can not be ignored, the design of the crossover and the speaker must be considered, and the Electrical quality factor Qe of the aluminum belt speaker is larger than the general speaker. 10 times, the resistance can be ignored. 4. The input impedance is approximately equal to the DC resistance: since there is no voice coil, the inductance is negligible, and the inductive reactance component of the impedance is negligible. The impedance curve of the aluminum belt speaker is similar to a straight line, that is, the input impedance is presented for any frequency within the frequency response range. Almost unchanged, similar to DC resistance. Designing a crossover is a lot easier. Therefore, the aluminum belt type treble impedance is almost constant, and has an excellent frequency response curve in the high frequency band, and does not start to decay until it approaches 40Khz. 5. The belt speaker has no “front chamber effectâ€: the aluminum belt speaker is designed like all flat film speakers without the front cavity of the vertebra speaker, so there is no anterior chamber effect, and the frequency response curve is easy to smooth. Second, the composition of the aluminum belt speaker The aluminum belt speaker is generally composed of a magnet (magnetic circuit), an aluminum foil diaphragm, a transformer, a casing, and the like. Let's talk about these parts in combination with the above features. Off-topic----Aluminum belt speaker was invented very early, no secret, many manufacturers' advertisements constantly describe the inherent advantages of those aluminum belt treble, and even blindly say that the diaphragm is light and thin, not facing its inherent The shortcomings and technical improvements are one of the differences between many Chinese companies and foreign innovative companies. 1. Magnetic circuit: In the previous section, the problem of insufficient magnetic flux was mentioned. The magnetic circuit of the aluminum belt speaker mainly uses horseshoe iron, and the magnetic conductive plate is narrowed at the air gap to increase the magnetic flux density. But this often does not maximize the BL. 2, diaphragm: This is one of the most exquisite, one of the most learned places. 1) Wrinkles - We generally believe that the ribbon speaker design is oriented as a flat film speaker. Because the flat-film speaker frequency is flat and natural, not only high-frequency speakers, like Martin. Electrostatic flat-film speakers such as Reagen pursue the superior performance of wider frequency response. It is a pity that the diaphragm of a typical aluminum belt speaker is made into a pleat shape, not for the sake of good looks, but to prevent deformation and sagging, because it is too light. Therefore, from the sound quality, I have been discounted, and my heart is always unhappy. 2) Safety---The general aluminum belt is very afraid of the wind, the life is not long, afraid of moisture deformation, no one dares to blow the aluminum belt treble? There is a sandwich composite diaphragm structure, not only does not wrinkle, but also promises not afraid of the wind Blowing! The reliability of the strength is greatly increased, which avoids a lot of money to buy back to the heart of the East. 3) The thinner the better?-----Many manufacturers like to use thickness as the sole standard for measuring aluminum belt speakers. In today's production technology, we are not "thin" than those who are aluminum foil, but who is more than aluminum foil" It’s nice! Light and light is good for the upper frequency limit, but not as thin as possible, just like a woofer. If you are thin to a certain order of magnitude, you should consider other issues such as rigidity and tone. 4) Directivity: The design of the diaphragm and the design of the front cavity also affect the directivity. The directivity of the aluminum belt tweeter is very uniform within 90 degrees. The subjective listening sound field is very wide and the sensitivity is lower than the nominal 2- 3DB is not surprising. Personally, I don't like the sound that makes the sound wave "squeeze out" in the axial direction through the special anterior cavity structure. The sound is very good at the beginning of the sound, and the sensitivity is very high. It is very "squeaky", except for the unnatural sound field. Some parts of the frequency response of the high frequency band are strengthened, and some parts are covered (throat effect), which is not delicate and natural. However, this is decided according to personal hobbies. I also agree that the sounds of the super-treble and horn match well. It is not suitable for pure treble and bass. 3, transformer Since the DC resistance of the aluminum diaphragm is very low, generally less than 1 ohm, Fountek's DC resistance is 0.02 ohm!, so in order to match the amplifier and the low-frequency speaker, an impedance converter-transformer must be used. Anyone who knows the amplifier knows that the output transformer has a great influence on the sound. It is not easy to minimize the distortion of the music signal through the transformer! Therefore, the transformer becomes one of the key technologies of the aluminum belt speaker, and this has never been It has not been mentioned in any manufacturer's brochure or manual! Wire, iron core, and feeding method are not technology. For example, the non-inductive feeding mode in which the parallel currents of the two coils are opposite is good to avoid the ordinary feeling, and the attenuation of the high frequency part is the lowest. Third, the top of the dome The dome-shaped speaker is one of the most widely used electric speakers in the current speaker. Its biggest advantage is its excellent mid-high frequency response and wide directivity. In addition, it has the advantages of good transient characteristics, low distortion and good sound quality. It is suitable for all home theater series speakers currently on the market. 1, structure The diaphragm of the dome-shaped speaker is generally designed to have a hemispherical shape to increase the strength of the diaphragm. The diaphragm of a dome-shaped loudspeaker is usually made of a rigid, lightweight material, and the diaphragm is generally small in diameter. In order to adapt to the playback of the intermediate frequency and high frequency signals, the dome-shaped intermediate frequency speaker has a large rear cavity as a resonance cavity of the intermediate frequency resonance frequency. Generally, a through hole is opened on the rear side of the diaphragm, and a sealed rear chamber cover is arranged on the rear side of the lower plate to form a cavity of a larger volume between the rear cover and the splint, and the cavity is usually also Filled with some sound absorbing materials, while the high frequency dome shaped speakers have no back cavity. 2, voice coil In tweeters, the voice coil plays an important role. In order to obtain a better high-frequency playback upper limit, the vibrating system of the high-frequency speaker is required to have the smallest possible quality under the premise of ensuring rigidity, and the voice coils of some Hi-Fi dome-shaped tweeters on the market are mostly used. A novel copper clad aluminum wire is wound. Aluminum has a smaller specific gravity than copper, and the use of copper-clad aluminum wire coil windings can reduce the quality of the voice coil, which is very beneficial for improving the frequency response of the tweeter. According to the current effect, most of the current in the voice coil of the tweeter flows through the surface of the voice coil winding wire, and the loss of the copper wire aluminum voice coil is almost the same as that of the copper enameled wire winding. In addition, copper also has good solderability. 3, classification The dome-shaped speaker can also be divided into a soft dome speaker and a hard dome speaker according to the softness and hardness of the diaphragm. The soft dome speaker sounds delicate and soft, expressive, more suitable for string and vocals, and does not appear stiff when performing percussion. In contrast, hard dome speakers have higher high-frequency sensitivity, and the tone often has a special "metallic taste." Although both speakers have a wide frequency range and a uniform frequency response, the diaphragm materials used are different and their timbre is slightly different. The soft dome speakers usually look soft and soft, while the hard dome speakers give the silhouette a clear feel. The diaphragm material of the dome speaker is usually divided into two categories, one is the soft dome. The vibration materials used in this type of speaker are mostly various artificial or natural silk products, such as silk, silk, and artificial. Fibers, etc., they appear delicate, soft and musical when playing music; the second type is hard dome, the speaker with this diaphragm, the diaphragm material is various metal films, such as aluminum foil, titanium foil and enamel foil, etc. They have a powerful impact on music playback, and the sound field has a clear outline, which is more suitable for percussion and pop music playback. There is also a diaphragm material between the two, usually divided into soft domes, which are PolyPropylene-based materials that are often used in low-end units for injection molding because of cost. If the quality is properly controlled, they can also make a very good sound, because they have the advantages of both soft dome and hard dome. The dome speaker is also a direct radiant speaker. Usually, in order to obtain smaller distortion, people will perforate the core and fill the soft material with high absorption characteristics. Because of its high frequency characteristics and wide radiation characteristics, it is widely used in high-fidelity systems. Frequency playback. The dome-shaped diaphragm is generally used for a mid-high frequency speaker. The material has a hard ball top such as an aluminum alloy and a titanium alloy, and the soft ball top such as a silk film, a cloth film, and a nylon film. The hard dome has a wide frequency response, strong sound penetration and good layering. The top of the soft ball is flat and the tone is soft. Hard dome speakers are generally good at replaying signals from analog sources. Soft dome speakers are generally good at replaying signals from digital sources. This is just a relative concept and it is not possible to draw a conclusion: the hard dome speaker is a low-end configuration and the soft dome speaker is a high-end configuration. If this is true, JBL, which uses a lot of titanium film, can't only produce low-end goods? In fact, hard-ball-top speakers are most suitable for three-way speakers, and soft-ball top speakers are much easier to use. On the other hand, the price of soft dome speakers is relatively low, usually only 1/3 to 1/2 of hard dome speakers, so commercial speakers use soft dome speakers. However, in home theaters, because the sound dynamics are large, and the dynamics of the soft dome speakers are small, the sound is more prone to hair at high power, so pay special attention to this when purchasing. 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