Crossover: IIR or FIR?

[watchnerd]

For the hard of understanding, please would you explain why the measurements show the filters are "screwed up"? It didn't obviously read that way to me. Thanks.

This, from the other thread:

"Order
LP=>-6dB ... -6dB=>HP
HP=>-6dB ... -6dB=>LP
1st 1.733 ... 0.577
2nd 1.000 ... 1.000
3rd 0.765 ... 1.307
4th 0.643 ... 1.556

So for 2nd order crossover you can use this without adjustments. 1000hz is 1000hz crossover point.
But for example 1000hz 1st order crossover point are... low pass is 577hz and high pass is 1733hz. "

It certainly doesn't fit the textbook definition.

Textbook definition of a 1st order 1000Hz high/low pass filter should be 6 dB down at an octave interval, i.e. 500Hz and 2000Hz.