magnetostat
Magnetostats are flat-panel loudspeakers, comparable to electrostats, with the difference that the diaphragm is moved by a magnetic field and not by an electrostatic one.
The freely moving diaphragm is a lightweight plastic foil diaphragm with a metal layer vapor-deposited in strips. It is located in the center between the permanent magnets arranged on both sides. When current flows through the metal coating, the membrane is moved in one direction or the other, depending on the direction of current flow, which generates the sound.
Magnetostats are suitable for the tweeter and midrange. The diaphragm sizes range from about 2 cm to 10 cm. There are such speakers with much larger diaphragm areas in the meter range also for the low frequency range.
Magnetostats are comparable to electrostats in their characteristics. They have a good impulse response and are not very pronounced in the low frequency range. Therefore, they are often tweeters.