Ribbons are difficult to integrate with the drivers. The Axioms enjoy a pretty seamless integration throughout their frequency range.
I had a Merak center channel, don't recall the designation, twin 6.5" and a 0.75" Titanium tweeter. Swapped in a pair of Axiom aluminum 6.5s and cobbled a tweeter/capacitor from a Reference de Capo 3a I found on ebay in place of the Axiom Ti tweeter. The Reference 3a did not use a cross-over, much like the Axiom M3s, just a cap and a resister, allowing the driver to mechanically roll off where the tweeter picks up. It's actually a stunning sounding speaker.
I modified some Radio Shack super tweeters with Solen caps. I think they help. Dogs love 'em.
