Hey man, I don't make this stuff up. Just a poor soul trying to make sense of all this.Here's a couple of links with some info. Interested in hearing your thoughts, Adrian.
http://www.marchandelec.com/xm46.htm
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
(sorry, but don't know how to include multiple links)
Gar.