Hand built speakers (They took me two years to build and I am a fairly accomplished woodworker). The lower cabinets house one 15" woofer and one 12" woofer. The upper cabinets house two 6.5" mid/woofers, one 5.25" midrange and three tweeters. Everything is hooked up in a four ohm impedence. Needless to say the speakers are extremely power hungry. These speakers do a pretty good job at testing the ability of the M200's (both from a sound quality point and from a load point). I can vibrate things in the house all the way down to about 15Hz and the highs are crystal clear (no hiss, static, crackle or anything normally associated with tweeters). Of course you have to spend a good bit of money on high end tweeters and crossover components (NPE capacitors and iron core inductors aren't going to cut it).