I removed these & put the 5.5 M drivers in the PAWA horn (had to enlarge the hole to do it of course.
I then fired them up with a 2a3 SET amp & a modded NOS TDA154a chip Phillips Cd player.

Initial Impressions:
The 5.5M drivers are a very significant improvement over teh 4"ers. I think Dave has really made a lot of changes that were needed. Let's see, much less IM distortion of course, and they sound noticeably fatter than the 4"ers in the midbass. The plug seems to help the midbass, midrange & treble considerably.
I am listneing to them full range without a sub, and frakly, for music the bass is very adequate!
I measured them with a rat schak meter, and they seem to go down to about 70 Hz, and then drop, but honestly, they sound more like 45Hz drivers to me with music. maybe becuase it is a horn, the bass response was not measured accurately by the rat schack meter at my lsitening distance of about 15 feet.

The amazing thing is the 100 Hz to 5,000 Hz response...very very flat within +/_ 2 db in my listening position! Very nice.
The one drawback I can see is that in the 6000-10000 Hz range they seem to go up by about 10 db, which may just be that they need break in. Anyway, ther eis not much program material over 5,000 Hz, so the subjective effect is that of added air with a slight treble sheen to higher voices & instruments (exagerrated 2-3rd order harmonics maybe?). Very subtle, and really not too bad at all.

I am listening to them with the drivers almost facing straight ahead (almost no toe in), and the imaging, etc are dead on. Very clear and nice with very goodbass for music. They ar about 3 feet from the side wall and about 5 feet from the back wall in a largish room.

I'm going to keep these in the PAWA horns, and have ordered another pair from DAve as a spare.

Will keep you all posted as I listen more!
-akhilesh