Subwoofer and Mains Filter - Problems?

[technikspezi]

Now the best filter order to use is going to be different for every speaker, enclosure etc but a good place to start is 80 high and low pass with a fourth order filter.

Thanks for your detailed response. Is there any kind of "rule" to choose the filter order? What is it depending on the speaker? Actually I have set the filter to 2nd Order. But I will try 4th order also. Can I try to use different ones for the subwoofer and the mains? So for example using 4th-Order with the mains and 2nd Order for the Subwoofer?

How will the filter order interact with the phase of the sub?

Thanks