Drivers

Moving coil

In 1924, two General Electric researchers, Chester W. Rice and Edward Washburn Kellogg patented the moving coil loudspeaker, the mother of all loudspeakers.

 

 

 

 

 

Electrostatic

Electrostatic loudspeakers use a high voltage electric field (rather than a magnetic field) to drive a thin statically charged membrane.

 

Although patented in 1929, the electrostatic loudspeaker did not reach commercial success until the 1956 with the appearance of the British-made Quad ESL-57. Electrostatic speakers (especially the old Quads) are renowned for their beautiful midrange and their frailty. However, if you put more than 20 Watts to them, or try for more than 100 dB of sound, and they are toast. They are the Jaguar XKE of the speaker world--beautiful, but fragile.

LifeTips

 

Ribbon and planar magnetic loudspeakers

A ribbon speaker consists of a thin metal-film ribbon suspended in a magnetic field. The electrical signal is applied to the ribbon.

 

Magnepan is famous brand producing full range ribbon speakers.

Apogee Caliper Signature

 

AMT

Air Motion Transformer (AMT) is a loudspeaker invented by Dr. Oskar Heil

Adam Audio is one of the brands using the AMT for midrange/tweeter

 

Bending wave transducer

You can compare it a bit with throwing a stone in the water.
The voice coil generates a ripple in the cone.

 

 

Manger bending wave transducer - Soundlabs Group

 

The Walsh speaker was one of the first.

A history van be found here.

Walsh

German Physics

German Physiks Troubadour 80

Flat panel

The diaphragm of a Distributed-Mode Loudspeaker (DML) vibrates in a complex pattern over its entire surface. Close to the diaphragm the sound field created by this complex pattern of vibration is complex also, but a short distance away it takes on the far-field characteristics of the DML radiation. This is close to the directivity of a true point source - i.e. approaching omnidirectionality - even when the diaphragm is quiet large relative to the radiated wavelength.

 

Parrot Zikmu using the NXT flat panel

for midrange and tweeter

 

CinosCinos flat panel

 

Plasma

acapella

Acapella ION TW 1S

The Plasma Speaker Homepage

Ionic wind

In an electrostatic air mover, the corona discharge ionizes the air around the emitting electrode. As the ions stream across an open space to an oppositely charged collector electrode, they pull other air particles with them by means of electrostatic attraction, thus creating air movement.

Tessera plans to use this for silent cooling of e.g. laptops.

Kronos Advanced Technologies Inc uses the same technology.

What about using it for creating a speaker without moving parts?

 

 

 

EFA Loudspeakers

 

References

  1. History of the Speaker - Green Mountain Audio
  2. Loudspeaker history - Centroid works’s Weblog
  3. Electric motors and generators - The University of New South Wales, Australia
  4. The different speaker collection - Sound Image
  5. Loudspeakers - WikipediA