Blacked out some parts, but this is some of the math behind one of the recent series 6th orders:
Series 6th orders are fun.
I really want to do a home audio Parallel 6th order, for myself. Or some variation of a horn. I know parallel 6ths, paired with the right woofer, would do what I want it to do, inside of a house. My ported, almost-full-range towers play down to about 40-45 hz with authority. I don't even have the towers crossed over, as far as the 3 5.25's in each tower, on the low end (no high pass filter). With the right sub, I could easily get a decent pressure response from ~20 hz to 50 hz or so, which is all I would need. The size of the 6th might be limited, so I may have to use a smaller woofer, and I would use it more for music than anything. So I might miss some lower 20's, depends on the woofer type I could fit.
This little sealed 8 that's like half as old as I am is just not cutting it, below my desk. My towers play lows just as good as it does, at least audibly. Decisions decisions. Maybe I should just start building myself horns until I nail the process.