Lansche plasma tweeter replacement every 5000 hours.

Interesting.  I have been interested in these tweeters for years but never had the ability to hear them.  Years ago I wanted to add supertweeters to my main speakers and was looking into plasma.  I had no idea they had a limited number of hours.  The permanently charged stat tweeters I chose work well, but it appears they have gone out of business.  I have a great knack for finding gear from companies that go under.  LOL.  However 2 have recently been revived, TTW turntables, and the sale of Velodyne to someone actually interested in running an audio business.  

The ozone issue often gets brought up.  Although these types of speakers produce ozone it can be readily catalysed back to O2 using several methods and/or adsorbed by activated carbon.  Ozone is very unstable and typically only lasts around 20 minutes - it is easy to smell and avoid.  There's more than ozone to worry about (NOx for example) and many other things that makes these devices challenging to design (see

for more detail). But these issues are what makes designing them interesting and the problems can be overcome.

Thanks for the info on massless. I have asthma so ozone affects my ability to breathe well.🙃