Here are some very unscientific impressions of the C2. I initially connected it to the right channel of my Onkyo 706 AVR, switched the mode to CD analog mono and did about 20 hours of break in time in order to satisfy the dire warnings posted by Mirage in the manual. They actually recommend 100+ hours but I think 20 is plenty. I don't blast my speakers to ear shattering levels anyway. Did I hear a difference between hour 1 and hour 20? Not sure. I didn't have them turned up real loud.
After the 20 or so hours, I unhooked my C1 from the main system and brought it to the living room to compare to the C2. Their stand was the C2 box, so it wasn't the best of speaker stands. The C2 is a lot deeper than the C1; the fronts of the speakers were about 2-2.5 ft from the wall.
The most noticeable difference was in the bass. The C2 has very strong bass and it actually was sort of overpowering. However, it could be that it was placed too close to the wall plus being on a cardboard box wasn't the best thing to have it on. I'd say this would make a good main speaker. Mids and highs were very clear and lifelike. It has a fuller, richer sound than the C1 which it should considering the larger woofers. This informal evaluation was done listening to several well-recorded CD tracks played in mono.
I then put the C2 into the center position in my main room. It was put on top of Auralex Mopads which were on top of a wooden television riser/stand which itself was sitting on an Auralex Subdude (yes I know, pretty crazy but it looks fine). It is sitting out in front of the TV, with the front of the speaker being 4' from the wall.
Since my UMC-1 has no mono mode, I played several well-recorded CD tracks, left channel only. I switched cables between the C2 and the left OMD15 (didn't compare the C1.. it was still in the living room). I also level matched the speakers - the C2 is 3db less efficient. This time the bass was not so strong. I don't know if that is a function of playing only the left channel or because of the dampening effect of using the Auralex products, but the C2 was very well balanced. It reaches pretty low in the bass but everything was in balance - no one characteristic stood out.
Compared to the 15's, the C2 has a better midrange. It is cleaner - the 15 has a little more resonance to voices and the C2 sounds more natural or lifelike, female voices in particular. The highs were comparable. My room is not the best for bass because of the room nodes, but both the 15 and the C2 had good bass with the C2 perhaps tighter. For sure, the bass was not as prominent as when it was hooked up to the Onkyo in the living room. In my main setup, the C2 was connected to an Emotiva XPA-3. The 15's are connected to Emo XPA-1's. My comparison was done with two different Emo amps but I don't think this would make much difference in the sound. I do want to say that I feel the Onkyo AVR is not adequate to drive the 28 properly. It just didn't seem like it had enough power. The Emo amps - no problemo.
I didn't have a whole lot of time yesterday so I want to do more listening. I listened to a couple of scenes from the Kill Bill BD that I like to use to evaluate the 5.1 sound. It sounded great. The C2 is authoritative when it needs to be but it blends very well. When doing the level matching using a Radioshack SPL meter, I could tell it doesn't blend as well as the C1 but it is still a close timbre match - you can tell they are from the same family. Dialog was crisp and clear, pans from one speaker to another were seamless. It has great dynamics.
Overall: I still need to do more listening but as of now the C2 is a keeper. I wouldn't mind having 3 across the front if I could figure out how to make this behemoth fit on the left and right (it is 25" wide). It has very natural, clean and balanced sound with good dynamic range. I especially like the midrange. It's also a gorgeous speaker. Given that I don't think I can fit them on the L/R, I will just have to keep an eye on Vann's to put the 28's on a big sale.
My wife's reaction: "are you going to sell that other one?" I said yes, as long as this new speaker (the C2) sounds good. "Oh, okay, I don't mind if you buy new stuff as long as you sell the old stuff."
I will post more impressions after I have a chance to listen more.. which is a problem since during the week I don't have much time.