Alcone low/mid driver

First I have to say I have no own experience with Alcone Drivers but I have several German DIY speaker magazine issues with various tests of single Alcone drivers as well as complete speaker kits of them.
Also for me they seem to be fair priced and they are solid engineered drivers - no junk drivers.
The frequency response alone tells not the hole truth about them.
Admitted, the aluminium cones have a nasty higher frequency peak and ringing but this is the case for almost any alu cone driver and as it is normal for many rigid cone types as kevlar, carbon, ceramic and the like. Actually below the nasty high frequency peak the Alcones are very linear and behave quite well as also can be seen from the waterfall diagrams.
To give good results those drivers need a high slope lowpass x-over to give enough attenuation or/and maybe a notch-filter in order to remove the high frequency peak.