Editing Tweeter (section)

===Plasma or ion tweeter===
Because ionized gas is electrically charged and so can be manipulated by a variable electrical field, it is possible to use a small sphere of [[plasma (physics)|plasma]] as a tweeter. Such tweeters are called a plasma tweeter or ion tweeter. They can be more complex than other tweeters (plasma generation is not required in other types), but offer the advantage that the moving mass is optimally low—if not relatively massless and so very responsive to the signal input. The early models of these tweeters were not capable of high output, nor of other than very high frequency reproduction, and so are usually used at the throat of a [[horn loudspeaker|horn]] structure to manage usable output levels. One disadvantage is that the plasma arc can produce [[ozone]] and [[NOx]], [[poisonous|poison]] gases, in small quantities as a by-product. Because of this, German-made Magnat "magnasphere" speakers were banned from import to the United States in the 1980s. Any modern design uses catalysts to reduce the gas output to negligible quantities.

In the past, the dominant manufacturer in the US was DuKane near St Louis, who made the Ionovac; also sold in a UK variant as the Ionophone. [[Electro-Voice]] made a model for a short time under license along with DuKane from the inventor Siegfried Klein. These early models were finicky and required regular replacement of the cell in which the plasma was generated (the DuKane unit used a precision machined quartz cell). As a result, they were expensive units in comparison to other designs. Those who have heard the Ionovacs report that, in a sensibly designed loudspeaker system, the highs were 'airy' and very detailed, though high output wasn't possible.

In the 1980s, the [[Plasmatronics]] speaker also used a plasma tweeter, though the manufacturer did not stay in business very long and very few of these complex units were sold.