Wednesday, August 2, 2017

Ionovac and Ionofone tweeters

Ionic speakers go way back, even before other types.  The first ionic speakers were demonstrated in the late 1800's.

The 'modern' ionic speaker is the Ionovac tweeter (and it's Ionofone cousin) which were invented in 1946 by Siegfried Klein.  They were used in a variety of speakers, one being the ElectroVoice Patrician system.

The Ionovac has smooth and extended response into the ultrasonic free of resonances.  However, the basic design is plagued by relatively high IM distortion at high output levels.  Early units required frequent replacement of the quartz emission tube and this only got somewhat better over time.  There are also regular amplifiying tubes that need periodic replacement.

The Hill Plasmatronic is mentioned but based on a different concept.

I would think the Iverson Corona speaker is a full range version of something more like the original Ionovac--which is often called a corona speaker.

Another issue: ozone is definitely created.  That kills the idea for me.

This builder says it is safe because it is actually very little ozone.

This all seems silly to me now when it's clear you can have 40kHz response with relatively low distortion from a fabric covered dome, in the Dynaudio D21AF or Vifa NE19VTS.  The domes have very damped high frequency resonances.  Also, an endless variety of ribbon tweeters.

Update: I see the problem with dome super tweeters now.  The problem is dispersion.  Where the wavelength gets smaller than the dome (10-20kHz) it begins to beam more and more.  The dispersion quickly falls to nothing, typically around 30khz.

Electrostatic panels beam also, but since they are fairly wide to begin with, the beaming isn't quite as narrow.

Ionic drivers can be omnidirectional.  The "corona" naturally radiates in all directions.  Or they can have whatever dispersion you engineer your horn or waveguide for.

About the only other trick for that is what I already have (and need to get fixed): the Elac 4PI's.  The 4PI an omnidirectional speaker, in which the ribbon is almost a complete circle, suspended in a toroidal field.  This is, indeed, a kind of engineering miracle.

Replacing the left Elac with a D21AF has resulted in a huge increase in the audibility of beaming type artifacts as I move around the room, far beyond what I had noticed beforehand.

Adding a back dome (like the Vifa NE19's I now have) might help somewhat, but I doubt it would do the job as well as an omnidirectional tweeter.

Well there are other trick, in general you can use horns, acoustic lenses, and other tricks to make a normal beamy driver into a wide dispersion or omnidirectional one.  The newer Walsh-type drivers by German Physiks I think have pretty good response into the ultrasonic.  The original Walsh units made by Ohm did not have super extended HF response.

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