Pseudo-Coax 18" woofer. 3-way passive 1st order series XO. Cardioid system.

[youknowyou]

I suspect it is sized to adjust the acoustic slopes to work together, lowpass for the woofer and highpsss for the mid perhaps.

interesting!
I should then probably make a couple of mid/hf baffle of different size and measure to find the best size for the system.
thx!