I want to post this link, but I can't get it to work. These speakers were made in the 50's & 60's. I'm sorry but you have to search for "Karlson Speaker", then click on results for the home page. This could be something "WAY COOL!!!" The math to this is way over my head, but someone here, I know, could decypher it. They have a K18T model in the works.