I'm certainly not saying that these things are the last word in deep bass reproduction, but neither my cousin nor I have experienced any real problems with one-note bass or similar distortion problems. I think, as with any design, it's a matter of making the right compromises. I'm very satisfied with mine - especially since they've made it possible for me to get real extended deep end with little cost. They cost ~$150 to build.

I must say thatI think that some of the reason for the bad reputation this principle have, is that it's so widely used in cheap 'package type stereo & HT systems, where it's mainly used to at least give an impression of bass to very small satelite speakers with no sound under ~250Hz...