Paul and some others may be interested in this article showing the design process for a FE166E based loudspeaker driven by a single-ended amplifier:
newbielink:http://www.diyaudio.com/forums/diyaudio-com-articles/158899-arpeggio-loudspeaker.html [nonactive]
A thread to discuss the loudspeaker can be found here:
newbielink:http://www.diyaudio.com/forums/full-range/160614-morgan-jones-arpeggio-loudspeaker.html [nonactive]
I love watching engineers at work.