Speakers you can currently buy as a plasma speaker or with a solid-state massless speaker built in:
Vaugn Loudspeakers’ Plasma Signature
Lansche Audio Corona
Acapella Ion TW-1
The plasma, corona and ion speakers in these designs are all the same type – but with completely different names!
Is a corona wind the same as an ion cloud? Could be, but maybe they are force fields as well.
Is my Ionofone like your Plasmasonic? Perhaps they both are like an Arc One.
Let’s start at some basics. An electroacoustic transducer, that which takes an electrical signal and converts it into sound waves, is called a loudspeaker. The word speaker is synonymous with loudspeaker – although older references may write ‘speaker as if shortening the word loudspeaker.
A conventional loudspeaker with a cone, coil and magnet is typically known as a dynamic speaker. An electrodynamic loudspeaker to use its full name, also electromagnetic, but these are less often used because everyone knows what a dynamic loudspeaker is. It is after all the most common type of speaker by far and as a result it is what most people know as a speaker or loudspeaker without going any further.
There are a small variety of other speakers that might be put into a category of “moving mass”. These can be related to the dynamic speaker but have different names to distinguish them from the cone/coil/magnet construction. They are often electrodynamic but have names such as ribbon, balanced armature, air motion transformer (AMT), planar magnetic, orthodynamic, isodynamic, magnetostatic, distributed mode (DML), MEMS etc. In addition to dynamic moving mass speakers there are most notably the electrostatic, piezo ceramic and magnetostrictive types.
There has been little regulation or standardisation of naming as they typically get named by the inventors, related to marketing names, what they are made of or the physics employed. However, in general most of those names describe their specific technology.
This doesn't apply to massless loudspeakers.
So in the massless loudspeaker category there are six distinct types.
Type one – a plasma speaker that uses a glow discharge to create sound. The mechanism is actually thermal as the temperature of the plasma is varied which in turn varies the heat of the air which in turn varies in expansion.
Type two - a plasma speaker that uses a brush discharge to create sound. This also creates sound with the thermal mechanism above.
Type three – a plasma speaker that uses a corona discharge to create sound. The mechanism is ionic or electric where ions and/or electrons move through the air creating a wind which varies with the electric current.
Type four - a plasma speaker that uses an arc discharge to create sound. The mechanism is thermal as per type one. This is a hotter arc that runs at high current.
Type five – a flame speaker that uses a flame modulated by a high voltage (or magnetic field) to create sound as per the type one.
Type six - a thermal speaker or thermodynamic type – the heat of a mass (perhaps a wire) is varied and this varies the temperature of the air around it causing it to expand/contract as per the type one. So although a solid mass is involved the heat of the air is the active part of the speaker.
The first four types use plasma, ions and electrons in varying amounts with varying physics principles being employed and in physics should be described as electrohydrodynamic (or electro fluid dynamic or electro-aerodynamic).
The main point of discussion later is around the type one and three, glow and corona discharge.
The type two brush discharge is often used for physics demonstrations and public displays and is often found in self build kits where a tesla coil is used to create very high voltages which are acoustically and electrically noisy. This type doesn't lend itself to the use for accurate sound reproduction. Most of what applies to type one also applies to this type. Most often referred to as a plasma speaker.
The type four arc discharge was derived from arc lamps in the late 1800s after observing the noise that it made. It would still be viable but is has not been used since the early 1900s musical instruments for accurate sound reproduction. Its mode of operation is similar to the type one and is generally referred to simply as an arc speaker.
The type five is also seen in physics demonstrations and also doesn't lend itself to use beyond a curiosity, but it was the first of these types to be found and very popular in the 1800s followed by a small resurgence in interest in the 1960s. It has almost always been referred to as flame, with words prefixed with pyro-.
Only recently has the type six started to be investigated as the technology to produce the thin wires and drive them hasn't been available until now. So there is potential and naming wise it is largely referred to as thermal and words prefixed with thermo-.
The majority of work however has been done on the type one and three when it relates to the accurate reproduction of sound and their naming is the main issue.
Type one – a plasma arc is created in the air strong enough that it is in its glow discharge form. This is typically a high voltage plasma arc. Sometimes the plasma is created between two electrodes, sometimes at higher voltages from one.
It can be modulated in a number of ways and a number of different methods of supplying the high voltage can be used. In all cases a distinct area of glowing plasma can be seen. Plasma is ionised gas. The ions (electrically charged atoms or particles) and electrons in the plasma both create it and allow electricity to flow through it. Plasma is very hot, heating the air around it. If the intensity of the plasma is varied, e.g. at audio frequencies, the air around it varies in temperature which in turn causes it to expand/contract at the audio frequencies creating sound.
Type three – a corona discharge is created on sharp electrodes. When a high voltage is present on a sharp point, on a sharp edge or a fine wire, the electrons will fly off it creating a corona discharge. The tip or edge will faintly glow with a corona (a class of plasma), only visible in low light. If presented with a nearby ground point the electrons and ions charged by the electrons will flow through the air to that point, this effect is likely dominated by the electrons. As they do so they collide with air molecules imparting motion and creating wind. If you modulate the supply in some way the resulting air speed will vary. If you do that at audio frequencies it produces sound.
So simply put, type one you see a plasma arc, type three you don't.
When it comes to naming the type one and three are a mess. They are both types of plasma and contain ions but they create sound using different physical principles. However they often use the same name interchangeably and as a result people often misunderstand the underlying principle at work for a specific speaker.
They have both been referred to as the following (at least), not including most brand names:
Force field (!)
The most commonly used term over all is plasma speaker and the most common type of that plasma tweeter. This can be extended to plasma arc loudspeaker. This is most often used to describe type one, where there is a visible glow plasma, and this is by far the most common commercial design.
Even near its early conception, this type of speaker was described as ionic and called an ionophone (later ionofone, ionofane etc. used as brand names). The use of ions in the naming of type one is also common. Yes plasma is an ionised gas and so it is not wholly inaccurate, but the mechanism creating the sound is the heating of the air by the plasma.
In comes the type three. This type has only once been seen in a commercial product, the Plasmasonic, otherwise just a few prototypes and demonstrations. It is rarely described as a plasma speaker, although it has been and it is in the first commercial name. Early on the term corona wind was used but most often now it can be referred to as ion wind, ion cloud or just ionic or corona. Electrostatic has on occasion been used as a description, but the basic mode of operation does not involve a charge at rest even though there may be some static charge on or around the discharge points.
Further to that, testing has revealed that in the type three it is electrons that are the predominant cause of the air flow making it an electric speaker and only slightly ionic. Electric just seems to be too vague a description though, aren’t all loudspeakers electric in some way?
The use of the word corona and/or discharge nowadays has quite a different negative meaning to most people, so the type three can have a harder time finding a name.
This doesn’t pose a problem in most peoples lives but it is in the remarkably narrow field of solid state massless speakers. “That’s a nice ion speaker.”, “It’s not, I think you’ll find it’s a plasma arc wind transducer.”
So possibly the following simple names could be used for referring to them in general, even though they may not be totally accurate they merge well with most existing usage:
If the plasma is too bright to look at, call it an arc speaker.
Physically an arc discharge plasma electrohydrodynamic loudspeaker.
If you can see the plasma, call it a plasma speaker.
Alternatives, plasma arc speaker.
Physically a glow (or brush) discharge plasma electrohydrodynamic loudspeaker. This one is difficult to separate.
If you can’t see any plasma, call it an ionic speaker.
Alternatives, ion or corona wind.
Physically a corona discharge plasma electrohydrodynamic loudspeaker.
If you set something on fire to make it then it’s a flame speaker.
Physically a flame thermodynamic loudspeaker.
If you make something warm to make sound then it's a thermal speaker.
Alternative thermodynamic speaker.
Physically a solid state thermodynamic loudspeaker.