There are many types of announcement speaker system, which can be divided into electric type(moving coil), electrostatic (capacitance), electromagnetic (tongue spring), piezoelectric (crystal type) and so on. The latter two are used in rural cable broadcasting network, and can be divided into low frequency speaker, medium frequency speaker and high-frequency speaker according to frequency range. These are often used in a sound box as a combination loudspeaker.
1. Low frequency speaker For different speakers, the requirement for the quality factor, that is the Q0 value, of the low-frequency announcement speaker system is different. For closed and inverted containers, the Q0 value is generally between 0.3~0.6. Generally speaking, the larger the diameter of the speaker is, the larger the diameter of the magnet and the voice coil will be. The better the performance and transient characteristics of the low-frequency replay are, the higher the sensitivity will be. The structure of bass units is mostly cone-shaped, and a few are flat. There are many kinds of vibration film in the bass unit, including aluminum alloy vibration film, aluminum magnesium alloy vibration film, ceramic vibration film, carbon fiber vibration film, bulletproof fabric vibration film, glass fiber vibrating film, propylene vibrating film, paper vibration film and so on. The bass unit with aluminum alloy vibration film and glass fiber vibrating film are relatively small in general caliber, and the power is relatively large. While the bass unit with reinforced paper and glass fiber vibrating film is more accurate, and the overall balance is good.
2. Medium frequency speaker In general, the frequency response curve needs to be flat, the effective frequency response range needs to be larger than the width of the frequency band that it takes in the system, and the impedance needs to be consistent with the sensitivity and the low frequency unit. Sometimes the power capacity of the medium is not enough, then we can choose those with higher sensitivity and the impedance is higher than the medium of the bass unit, thus reducing the actual input power of the medium. The taper unit usually has two kinds of cone and ball. But its size and power are larger than those of the tweeter unit and suitable for playing the medium audio. The diaphragm of the Alto unit is mainly composed of soft materials such as paper and sericin, and occasionally a small number of alloy ball top diaphragm.
3. High frequency speaker The treble unit, as the name suggests, is a speaker unit for playback of high-frequency sound. Its structural form mainly includes the number solution, the cone basin type, the ball top type, the aluminum belt type and other categories.