I have long thought a paper diaphragm in a compression driver might give a very natural tone. I now see that the Faital brand of Italy is producing a 2 inch throat driver with a paper cone diaphragm and a nice high flux density of 2.1 Teslas from a Neodymium magnet.
It's frequency and impedance graphs look like it would be good for a 1000-8000 Hz 3 octave midband.
http://www.faitalpro.com/en/products/HF_Drivers/  model HMF200
Faital's model HF10AK might be a good choice for the freqs from 8000 on up.  The "A" models with Annular phase guide seem to graph better than the "R" models with Radial phase guide.

When I first came to the Decware forum there was quite a lot of DIY speaker building. Decware now offers so many ready built speakers, I don't know if  anyone here in the forum is interested in making their own, but I thought I would bring this driver to the attention of the forum in case it caught any one's fancy to try it. I have not seen a 3 way Imperial, but I don't know why it would not be a good idea.

I guess a horn the size of the Emilar 520 with approximately 10 x 20 inch outlet would be wanted to give a 500 Hz acoustic cutoff one octave below the electrical cutoff.  

Brian