Hello Jim,
Interesting that you bring up horn tweeters, currently I am running an 8" mid/woofer with two large piezo horn tweeters angled outwards for my center channel. This does not work very well, it is too harsh in the high end and the mids are not very distinct. This setup moves a lot of air though. My Wife and I often question each other about what someone said in a movie, and neither of us caught what it was. My H/K 630 I doubt is the problem in this scenario, it deserves better speakers.
A single speaker may be enough, but I am used to a lot more volume than I believe one M2i can generate. Two together I believe should be 3db louder than one alone. Please correct me if I am wrong here.
Thanks,
TonyM
