After conducting some listening tests I quickly realised that the 15WU Illuminator is not up to par in the midrange. It sounds a bit like listening through a sock, very dull and lifeless indeed. The Scanspeak Revelator series are clearly superior in this regard.

This outcome was considered from the outset of this project and there are 2 possible solutions -:
1 - replace the illuminator 15WU4741T with the revelator 15W4531G
2 - convert the speaker into a 3-way by adding the 12MU8731T midrange and a secong 15WU4741T.

I have chosen the 2nd option in the interests of acheiving the greatest possible performance.