Crossover: IIR or FIR?

[Waiski]

Im general, in electronics, cut off frequency is the one where there is 3dB fall (or raise) in signal power.
It would mean that 1-st order filter is properly implemented (-3dB fall at 250Hz). The other filters no so well. I have to admit that different types of filters could have different definitions of cut-off

Here's what I don't get:

Why would Devialet implement this in such a non-intuitative way?

Same here. I don't get it. They don't even inform us how to use the crossover... This is pure stupidity.

I've been wondering already long time why does the crossover give horrible sound. This is the reason. When properly configured the crossover does work really good.