Martin Audio MA18K - 2010 User Manual page 32

Set Shape=Linkwitz-Riley (You could also experiment with shape=FIR)
Edit CH2
All material © 2010 Martin Audio Ltd. Subject to change without notice
Set Frequency = 2000 Hz
Set Slope=24dB/oct.
Go to HP Filter, set Active=ON
Set Frequency = 2000 Hz
31