Bob,

Well, if you accept that speakers have group delay that increases with
frequency

Okay, but group delay is not a problem. The comb filtering that occurs in
the air from two drivers outputting the same content near the crossover
frequency is a problem. But that's a different issue, with no cure other
than a redesigned crossover.

I've played quite a bit with this business of pulling transients out front
of the stuff they stimulate via group delay manipulation.

How have you done that? Hardware? Software?

--Ethan