Good to see you- wadav-
interesting query. I suspect that much would be dependent upon how many names were on the original patent? If the 1st order cross-over patent was under Jim Thiel only- I do not see any problem(s) once it expires , no one else comes forward to file another claim.
Since Rob Gillum still holds a residence at Thiel -Kentucky, I wonder if he has a hand or stake in those loudspeaker designs?
Happy Listening!