IMO, the full-range magic is due to lack if phasing errors in the important 300-3000 Hz frequency range. This means no crossover 150-6000 Hz. Outside of that frequency range, you can do most anything you want and the magic will still be there. Best bet should then be a 4-6" driver supplemented with a sub and for the bat-eared, as tweeter. Some day, I'm going to suck it up and get a pair of DX55's and see what happens. For now, I think that the DX3 is the best overall full-ranger.Full-rangers CAN do bass. My bench mark is 40 Hz. If a full-ranger can get down to 40 Hz, then I'll use it in a single-driver speaker. Drivers I know that will go there are the FE167E, FE206E and FE207E. The F200A is the best of the bunch at the bottom. DX2 and DX3 go there. AN6 and AN8 go there. Last March, I took a pair of DX2 MLTL's to a Texas Bottlehead meet. They physically shook the floor on some organ petal notes.
Yes, full-range single driver speakers will do bass. The trade-off? Dynamic range. TANSTAAFL.
Bob