The book "High Quality Horn Loudspeaker Systems" by Bjørn Kolbrek and Thomas Dunker was released in November 2019. This website will keep you up to date with availibility and distributors, and we also provide extra material and errata. The book is now in its second print run, and most of the errors from the first print run have been corrected. 

Currently the book is available from Lean Business Audio and Parts Express.