The most common type of driver, commonly referred to as dynamic speakers, uses a light diaphragm or cone and is connected to a rigid basket or frame through a flexible suspension (commonly referred to as a bracket), which restricts the axial movement of the voice coil through a cylindrical magnetic gap. The dust cap attached to the center of the cone prevents dust (most importantly ferromagnetic debris) from entering the gap.

When the electric signal is applied to the voice coil, the current in the voice coil will generate a magnetic field, making it a variable electromagnet. The coil and the driver's magnetic system interact in a manner similar to a solenoid valve, generating mechanical force to move the coil (and thus the connected cone). The application of alternating current moves the cone back and forth accelerates and reproduces sound under the control of the applied electrical signal from the amplifier.

The following is a description of several components in this type of portable bluetooth speakers

Diaphragm

Diaphragms are usually made of conical or dome-shaped sections. Various materials can be used, but the most common are paper, plastic, and metal. The ideal material is rigid to prevent uncontrolled cone movement, has low mass to minimize starting force requirements and energy storage problems, and has good damping to reduce the vibration that continues to occur after the signal stops. Because its resonant frequency is determined by its use, there is little or no audible sound. In fact, the use of existing materials cannot meet these three standards at the same time; Therefore, driver design needs trade-offs. For example, paper is light, usually well damped, but not hard; Metal may be hard and light, but usually has poor damping; Plastic can be very light, but generally speaking, the harder it is made, the worse the damping. Therefore, many cones are made of some kind of composite material. For example, the cone can be made of cellulose paper, in which some carbon fibers, aramid, glass, hemp or bamboo fibers are added; Or it may use a honeycomb sandwich structure; Alternatively, it can be coated to provide additional reinforcement or damping.

Basket

The chassis, frame, or basket is designed to be rigid to prevent deformation, which may change the key alignment with the magnet gap and may cause the voice coil to rub with the magnet around the gap. The chassis is usually made of aluminum alloy, and loud speakers of heavy magnet structure, Or it is stamped from thin steel plate in the lighter structural driver. [19] Other materials, such as molded plastic and damping plastic composite baskets, are becoming common, especially for cheap, low-quality drives. Metal chassis can play an important role in transmitting heat from the voice coil; Heating during operation will change the resistance, resulting in physical size changes. In extreme cases, the varnish on the voice coil will be scorched; It can even demagnetize the permanent magnet.