I'd like to build a pair of these speakers, the 2226 drivers are easy to find for short money on ebay, I was pondering a 4430 design but the drivers are much more expensive and harder to com by. I guess the only real difference is that the 4pi's really need a subwoofer? They roll off rather steeply at 100hz while the 4430's are pretty flat until about 50hz, at any rate, may I have a set of plans please?
The four π loudspeaker sounds good without subs, but I would definitely suggest subs for the best experience. And subs are recommended not just for added extension but also for modal smoothing. So really, the gradual rolloff below 100Hz is not so much an issue, because the benefits gained from adding flanking subs are significant beyond extension.