But all this bantering is distracting from the purpose of my original post which is: LOOK AT MY PRETTY SUB.

If you must know, I did a sweep on the sub last night with the 4th order lowpass on the plateamp set at 40Hz and this is how it sound in room BY EAR from top to bottom:
- slowly starts to roll in at 80Hz
- pretty flat between 60-50Hz
- peaks up at 40Hz
- drop at 30Hz, but still strong
- quickly rolls down below 30Hz

You know, there isn't a lot of material under 50Hz anyway, so having something strong above 50Hz is great and can sound thunderous. I only meant to point out that while the three π isn't a sub, it does generate deep bass. So for a sub to get underneath it and provide significant output takes something tuned pretty low.

A horn shifts to being a direct radiator below its passband, and since the rear chamber is a rather small sealed box, it has a hard time generating a lot of energy under that point. That's why I wanted to provide a suggestion. If you were running one π speakers or something smaller, a 50Hz horn would have made sense to me but in this case I would have preferred a subwoofer with lower cutoff, that's all.