Thanks Jim, that makes me feel better about pursuing these as possible drivers. Do you (or anyone else) have any experience with the Bohlender Graebener RD series? They've got a pretty remarkable frequency response : 150hz-18,500hz. And they give you the flexibility of building either dipole or monopole. Seems like a pretty nice array could be built with one of these crossing over at 300-500hz to a line of woofers. I would think using woofers this low would simplify their choice and maybe you could get away with using less expensive ones (woofers that is).