Yeah, Altecs are pretty much horn loaded mids and treble, from 100Hz up. Lower registers are from direct radiation.What do you have in mind for OB bass? High Q woofer and large partition?
Ever thought of bolting a woofer directly to the wall? That makes something in between IB and OB. It's like a quasi-IB and you can sort of see it as a large sealed box that's leaky, making it similar to an open baffle. Something in between.