The commercially available loudspeaker loudspeakers are still dominated by hemispherical designs because the technology is mature and offers a decentralized bandwidth, while the materials used in the hemisphere tweeter include silk film, aluminum, and even Expensive beryllium metal and so on. In addition to the mainstream hemisphere tweeter, in fact, there are many different types of tweeter design units, including two tweeter also began to be used by manufacturers, namely, with high-pitched and high-pitched treble. Both are very similar in appearance, the same is a rectangular design and a protective cover. What are the differences between the two units?
The development of the aluminum treble unit is made by the early generation of the aluminum belt microphone, using a square appearance, but the aluminum treble is a metal film as a diaphragm, the film on the magnetic field, when the current will pass Produce vibration. Since the metal diaphragm made of aluminum is very light, so the response of the high frequency is very good, the highest frequency output can exceed 20kHz above the treble, but the defect is easy to damage, so the aluminum unit must be protected.
Aluminum tape design can provide higher frequency output performance, but in the same technology, the magnetic field between the magnetic field strength than the average tweeter is weak, resulting in lower energy output. But in recent years, many tweeter units have adopted neodymium magnetic as permanent magnet, increased magnetic field strength, enhanced high-frequency output sound pressure, but also to further reduce the unit size, reduce production costs, so that the general speaker can also use aluminum Belt tweeter, plus many manufacturers are also actively introducing aluminum belt tweeter to further push down the price of aluminum treble.
In order to enhance the high-frequency performance of the aluminum treble unit, in addition to the use of magnetic field strength, it can reduce the weight of the diaphragm, so some of the aluminum treble will use lighter film such as Kapton, plus aluminum conductive film manufacturing. Therefore, the market with aluminum treble is not necessarily all aluminum, but with synthetic materials and metal coating manufacturing, the English name for the Ribbon Tweeter, or "aluminum with tweeter" to call more appropriate.
The other is called Pneumatic Treble or AMT, which is developed by Dr. Oskar Heil in the 1960s. The principle of sound is completely different from that of general moving units or electrostatic units. Pneumatic unit is through a folding film, and in the bottom of the film with conductive metal, under the action of a strong magnetic field, the sound signal to make the diaphragm back and forth vibration, forced out of the air to produce sound waves. As the film is folded like a fan, the effective area of the 1-inch-width AMT is equal to the surface of an 8-inch unit, and the film is only a small enough to produce enough sound pressure. Although the pneumatic treble and aluminum treble appearance is somewhat similar, but the direction of vibration with the direction of the same direction, but the aerodynamic treble vibration direction and sound direction was 90 degrees angle.
The history of pneumatic treble is around 40 years. In the 1970s, AMT's technology was officially applied to loudspeakers, when ESS launched the AMT-1 tweeter. Later, many companies also began to produce pneumatic units, which are more well-known, including ELAC JET unit, Adam X-ART unit, ETON ER4 and so on. As a result of the use of a strong magnetic field neodymium magnet, so that the highest frequency response of pneumatic units to 50kHz.