The 12NDH-4 produces a good response in the PM90/60, the 12NDH- 3 gives an even better / smoother response but has less X-max. I guess it becomes a matter of where you want to cross to the subs etc. etc.
In the PM90/60 the response will not be flat, quite bumpy and MUST be EQ-ed flat. Because every thing is operating in the piston range you can fix it with EQ without any problems ... i.e. not sounding processed as some people say.
In the PMA60 the low/mid response will be flat.
What I don't know is how well the Carie PR614 will perform if you cross it lower than the recommended 800Hz. The PM60/90 needs to be crossed at 700Hz or less.
I am crossing it at about 680Hz on the PMA60 but its a big compression driver not having to do a lot of work. With the PM90/60 it will need to do a lot more work to keep up to the 2 horn load 12's. Not sure how the PR614 will go, it was not available when I started the project. I don't expect the spacing to cause directivity problems, its just the the horn MAY not provide enough loading for the driver if you cross too low - in this case I don't know.
The XT is specified to be useable from 500Hz, and I know RCF use the HF950 as low as 650Hz so these will work with the PM90/60.
The PMA60 was designed and built during COVID and as such I have had very little opportunity to test it in every application.
