Loud Speakers
The most common type of driver uses a lightweight diaphragm, or cone, connected to a rigid basket, or frame, via a flexible suspension that constrains a coil of fine wire to move axially through a cylindrical magnetic gap. When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the voice coil, making it an electromagnet. The coil and the driver's magnetic system interact, generating a mechanical force that causes the coil (and thus, the attached cone) to move back and forth, thereby reproducing sound under the control of the applied electrical signal coming from the amplifier.
Full-range Driver
A full-range driver is designed to have the widest frequency response possible, despite the rule of thumb cited above. These drivers are small, typically 3 to 8 inches (7.6 to 20 cm) in diameter to permit reasonable high frequency response, and carefully designed to give low-distortion output at low frequencies, though with reduced maximum output level. Full-range (or more accurately, wide-range) drivers are most commonly heard in public address systems and in televisions, although some models are suitable for hi-fi listening. In hi-fi speaker systems, the use of wide-range drive units can avoid undesirable interaction between multiple drivers caused by non-coincident driver location or crossover network issues. Fans of wide-range driver hi-fi speaker systems claim a coherence of sound, said to be due to the single source and a resulting lack of interference, and likely also to the lack of crossover components. Detractors typically cite wide-range drivers' limited frequency response and modest output abilities, together with their requirement for large, elaborate, expensive enclosures—such as transmission lines, or horns—to approach optimum performance.
Subwoofer
A subwoofer is a woofer driver used only for the lowest part of the audio spectrum: typically below 120 Hz. Because the intended range of frequencies in these is limited, subwoofer system design is usually simpler in many respects than for conventional loudspeakers, often consisting of a single speaker enclosed in a suitable box or enclosure.
Mid-range Driver
A mid-range speaker is a loudspeaker driver that reproduces middle frequencies. Mid-range drivers can be made of paper or composite materials, or they can be compression drivers. If the mid-range driver is cone-shaped, it can be mounted on the front baffle of a loudspeaker enclosure, or it can be mounted at the throat of a horn for added output level and control of radiation pattern. If it is a compression driver, it is invariably mated to a horn.
Tweeter
A tweeter is a high-frequency driver that typically reproduces the highest frequency band of a loudspeaker. Many varieties of tweeter design exist, each with differing abilities with regard to frequency response, output fidelity, power handling, maximum output level, etc. Soft-dome tweeters are widely found in home stereo systems, and horn-loaded compression drivers are common in professional sound reinforcement. Ribbon tweeters have gained popularity in recent years, as their output power has been increased to levels useful for professional sound reinforcement, and their pattern control is conveniently shaped for concert sound.
