Scott,
If you'd like some help in designing a passive HiPass filter ( for a 2450SL mounted to a M2 waveguide ) just ask.
There are indeed some usable measurements located within this thread which gives one a head-start for roughing-out a design.
( To move it forward beyond this ) you'll need to use REW to capture some response sweeps so that they can be compared to those already done by LHF member "sebackman" .
You also need to create ( with REW also ) an impedance sweep of a 2450SL driver on an M2 W-guide ( + then export that as an .zma file ).
Then anyone ( with network design software ) can conjure a custom HiPass after a bit of manipulation.
Having said that ( plus after using Robh3606 + sebackman's pics, then tracing them, + then turning those into frd + zma files ) here's what a network would look like ( following LEAPs lead in using 3-pole bump filter for the high-pass ).
For the sake of comparisons Robs 476mg is in black ( raw fr + with his @ network ), the 2450SL is green ( raw ) + blue ( network ), & then the ( raw ) 2451Be is represented in red.
- FYI, the traces from sebackman aren't that believable below @ 1000hz.
I had to use Robs 476mg impedance file as a standin for the 2450SL ( which is a real no-no in the design world > but it's a bit better than having nothing to work with ).
- That's another reason what you see above you can't take to the bank.
You might locate a 2450SL\M2 .zma file from sebackman ( since he had made an impedance file some years back ) .
The true value of this exercise is you that get an idea of the parts count ( of passives ) needed for a flat-ish hipass ( plus the need for sa couple PEQ, LCR notch filters ) .