Under the dustcap . . .
I can't remember the brand/model of these speaks, but the add I saw in Home Theater magazine was a 5.1 set of black spheres. The satellites were single driver (4"-5") with their dust caps (or whatever you'd want to term them in this case) shaped like a high frequency cone (a whizzer that's an in-ee instead of an out-ee). I'm guessing this is accompanied with literature explaining how important point source and time alignment are, yada, yada, yada.
What I'm interested in, is making something like this out of existing drivers. Would this actually work as well or better than whizzer cones? Other than needing to make sure that this is shallow enough not to not to hit the pole piece on the back stroke, are there any other physical considerations such as optimal shapes, depths, etc.?
How about considerations of what type of drivers that would be moded this way? I'm guessing that using a driver that's already bicone and trading this structure for the existing whizzer would be fine. Do you think that it would be okay to mod larger drivers (10"+) like this? Nothing with a large voice coil, of course, as they're already low passing themselves just due to the coil's inductance, but I've seen 10" and 12" PA drivers with whizzers (rated up to 9khz and 7khz each, though I've seen phase plug moded 10"ers rated up to 12khz). I'm guessing that an 8"er with a moderate Fs at best is going to be as far as you could go with any hope of getting full range performance, but I think it might be possible to go larger as long as you're willing to use a supertweeter.
I prefer to get as much bottom end out of a full ranger as possible and bring in a super tweet if necessary, so this seems like an interesting path of research. Any thoughts?