Editing Loudspeaker (section)

====Moving-iron loudspeakers====
{{Main|Moving iron speaker}}
[[File:Moving-iron cone speaker 1929.png|thumb|upright|Moving iron speaker]]

The original loudspeaker design was the moving iron. Unlike the newer dynamic (moving coil) design, a moving-iron speaker uses a stationary coil to vibrate a magnetized piece of metal (called the iron, reed, or armature).  The metal is either attached to the diaphragm or is the diaphragm itself.  This design originally appeared in the early telephone. 

Moving iron drivers are inefficient and can only produce a small band of sound.  They require large magnets and coils to increase force.<ref>{{cite book |last=Crowhurst |first=Norman H. |date=1959 |title=Basic Audio |url=http://www.tubebooks.org/Books/crowhurst_basic_1.pdf |via=Tubebooks.org<!--old public domain book; somebody republished a scanned copy on their website--> |volume=1 |publisher=John F. Rider Publisher |page=63 |access-date=April 30, 2024 }}</ref>

Balanced armature drivers (a type of moving iron driver) use an armature that moves like a see-saw or diving board.  Since they are not damped, they are highly efficient, but they also produce strong resonances.  They are still used today for high-end [[earphones]] and hearing aids, where small size and high efficiency are important.<ref>{{cite web |last=Hertsens |first=Tyll |title=How Balanced Armature Receivers/Drivers Work |url=http://www.innerfidelity.com/content/how-balanced-armature-receiversdrivers-work#IboPCt5E0YtmLTAL.97 |website=InnerFidelity.com |date=December 16, 2014 |archive-url=https://web.archive.org/web/20150914044126/http://www.innerfidelity.com/content/how-balanced-armature-receiversdrivers-work#IboPCt5E0YtmLTAL.97 |archive-date=September 14, 2015 |access-date=September 5, 2015 }}</ref>