The midrange is also Audax. Westlake could be using an OEM version that just looks the same, but on the Audax site it says "direct replacement.
http://www.audax-speaker.de/index.php?module=shop_articles&index[shop_articles][action]=details&index[shop_articles][data][shop_articles_id]=29&lang=en
I built speakers with an earlier version of this driver in the 1980s, so they've been around for a long time.
Tomas