My New Magnepan 1.7i's sound dull and lifeless on the top end...why?

I just bought a used pair of 1.7i speakers, in pristine condition and only 7 months old. I own a pair of .7s and wanted to upgrade. The 1.7i speakers sound bad. Dull, bassy, no high-frequency detail. I was hoping to get more low-end response, but I wasn’t expecting the dull, lifeless sound. I am very experienced in setting up Maggies. Magna Risers don’t help. Different amps don’t help. Tweeters in vs. out don’t help. Neither does moving the speakers and my listening chair help. I can get them optimized, but I can’t remove the shelf in the frequency response (about 5 or 6 dB starting in the midrange, so that the lower mids and bass are elevated). Is this how they sound? Is there a large variation from one pair to another? My .7s sound awesome in the same room with the same equipment.