Yeah, back when JM published his loading cap expose' I noticed that 2 kHz looked a better choice for the horn, but no clue what the woofer's response would be like and frankly wasn't that interested as the original's 1 kHz horn/XO had long since indelibly marked my teen brain, though did have a brief 'affair' with a then neighbor's 604E that we tried in his [my ex] built-in corner A7-500 system.

Historically, I don't even like 2nd order that much unless there's proper offset to wire in phase and LR 4th @ 360 deg disconcerts me above ~800 Hz due to HTRF, so pretty sure 720 deg. would do me in except down low where nobody will notice, but can it be 'unwrapped' with DSP? I mean the 0.21 ms delay is just for increased HF offset, right?

Have you done 604 woofer only response plots? I've yet to see one.

GM