I'd be cautious about some statements on QTS. For example the woofers used in the Bionors are QTS of .7
Don't get me wrong, I pay a lot of attention to it for types of drives etc but depending on the type of driver and enclosure/horn design the concerns vary.
The QTS being high in Bionor makes sense due to baffle design (open at back) and “infinite type” at front. For 95% of standard horn loading applications, low QTS is used. This example is unusual.