There are many catagories in loudspeakers. Loudspeakers can be sorted into eletrodynamic types, electromagnetic types, piezoelectric types, digital types and others by power supply methods; according to the diaphragm structure, loudspeakers can be classified into single cone, compound cone, compound horn, coaxial and others; according to the diaphragm style, they can be divide into cone types, globle-roof types, flat plat types, band types and others; according to replay frequency, they can be divided into high frequency, middle frequency, low frequency and full spectrum band loudspeakers; according to magnetic circuit form, loudspeakers can be sorted into outer magnetic ones, inner magnetic ones, double magnetic circut ones and shield ones; according to magnetic circuit propertise, they can be classified into ferrite magnet ones, boron neodymium magnet ones, alnico magnet loudspeakers; according to the diaphgram material, they can be divided into paper made and none cone loudspeakers.

A. Electrodynamic loudspeaker is the most widely used one. It produces sound by vibrating the diaphragm coming from the mutual acting force between voice coil and constant magnetic field. As forwoofers, cone types are in majority. As for mediant loudspeakers, the cone types and global-roof types are in majority while high pitch loudspeakers are mainly global-roof types and band types, and the horn types are widely used.

B. Structure of cone loudspeaker is simple, and energy transfer rate is high. The diaphragm is mainly made of pulp, or mixed with wool, silk and carbon fiber to strengthen its rigidity, internal damping and waterproof functions. The latest electrodynamic cone loudspeaker adopts non paper diaphragm meterial, suck as polypropylene, mica carbide polypropylene, carbon fiber, bulletproof fabric, hard aluminum foil, CD ripple, glass fiber and other compound materials.

C. There are soft global-roof and hard global-roof loudspeakers. Acoustics of soft global-roof loudspeaker is sweet and gentle; while the acoustics of hard ones is clear and melodious.

D. Radiation mode of horn loudspeaker is different from cone loudspeakers, and the sound spreads via horn after the diaphragm vibrates. The characteristics of horn loudspeakers are high electroacoustic conversion and radiation frequency, far distance, little distortion, narrow replay band.

E. Voice coil of band loudspeakers is coupled on the whole diaphragm. Alternating magnetic field arisen from voice coil interact with constant magnetic field, making band diaphragm vibrate and produce sound waves. The characteristics is quick response, little distortion, fine replay acoustics and good layering.