The midi range, not the tweeter, is the most important driver in a speaker.

@ Andy, yes the xover is critical. 
Which is why SEAS has engineered the xover for this Thor. The xover I have in my 2002ish Thors is the UPGRADE version,,which ain't saying much based on new technology since that time. in 2020, i will have madisound build a  new xover for the Thors,,all using Mundorf Silver/Gold,,not the SG supreme which are out my budget range. 
I did manage to buy  2 10uF Gold/Silver Sprene off Ebay at 1/2 price,, so will  ship these to Madisound and add the Silver/Gold caps /new R Ressist Mundorf and new coils,,The lower caps going to the low midbass i will use a  basic tin cap/Mundorf.
The Excel drivers will blossom with sound. The dead will come tIn 2020, i plan to make about 50++ vids documenting all my new tweaks. I plan to be #1 mod guy on YT. 

I think Joseph Audio's use of magnesium drivers shows this is possible. A combination of judicious low pass filter + notch filter can make these work, no?

The proposed solution does not really work. It gets rid of some of the left over phase shifted issues ...but...

Agree. Erik. That is where you herring is the most delineated. 

Many who build mediocre audio systems think this.