Tweeters are the speakers that reproduce the high frequencies. They are smaller than midrange and woofers because they handle shorter wavelengths of sound.
Dome Tweeters
These account for the majority used in Hi Fi. They are basically a moving coil speaker without the cone with the voice coil attached to the dome. It was found in the early days of speaker development that speakers with cones had a rapid fall of when trying to reproduce high frequencies. It’s a question of mass, after dispensing with the cone the mass is greatly reduced, and with low mass it becomes easy to reproduce high frequencies. They generally cover the range from 2,000 Hz to 20,000 Hz.
Cone Tweeters
These are smaller versions of a normal cone speaker but on a smaller scale. Being much smaller the mass is much less and this accounts for them being able to handle the higher frequencies. The suspension is stiffer than cone speakers because they move much less than cone speakers. The voice coils are also lighter because they don’t handles as much power as their larger counterparts.
Ribbon Tweeters
Ribbons use a thing membrane usually made from aluminium for reproducing the high frequencies. The ribbon is suspended in a strong magnetic field and because it is very light is able to reproduce higher frequencies than most other types, and well outside the audible spectrum. Ribbons have unique directional properties having wide dispersion horizontally but narrow in the vertical plane. This is particularly desirable for the reproduction of audio.
Piezo Tweeter
Piezo tweeters do not utilize magnetism and operate by voltage applied from the amp to the crystal causing the crystal to change dimensions and converting it directly into movement or sound. This process is called electrostriction.
Electrostatic tweeter
An Electrostatic tweeter works the same way as an electrostatic speaker. It has two screens either side of a thin diaphragm that is coated with a thin conductive coating. The screens have high voltage applied to them and this attracts or repels according to the voltage applied.
Air Motion Transformer
The AMT works by pushing air vertically from a pleated diaphragm. This diaphragm consists of folded pleats arranged around aluminium struts held in a strong magnetic field.
Horn Tweeter
This can be any above tweeter housed in a horn. The horn offers greater coupling of the tweeter to the air to improve efficiency. The tweeter used in this application is called a compression driver.
Plasma or Ion Tweeter
Ionised gas is electrically charged, and thus can be manipulated by a magnetic field. These are more complex because they require the production of ionised gas. They have advantages in that the moving diaphragm is very low mass.
