Best Subwoofer Setup

[Waiski]

for a correct implementation of a sub you need to measure the frequency response at your listening position.
I have an 18db room resonance at 45Hz, so I have to use the highpass of the Devialet (50Hz, 24db/oct) to bring this resonance down. Now I have two regions where I need to add bass again, from 20 to about 43Hz and from 47Hz to maybe 130Hz. I let my sub (B&W DB1) play up to 120Hz and use a miniDSP 2x4HD to correct the bass response. The internal DSP of the DB1 is not precise enough and has some limitations, the miniDSP is a big step up. This gives a nearly linear bass response with only a smaller loss of 3-4 db in the range between 100 and 120Hz.
This is room dependant and would need a second sub to get rid of it.
But without measuring equipment you will not come to a nearly perfect solution.

Devialet doesn't have 24db/oct crossover.
Devialet crossover is something totally unusual. My friend who does design loudspeakers said it is something like Dessel (bessel with Devialet twist).

Filter order 4. is actually -12db @ cut-off frequency. Also the crossover point is not on the 50hz.

It also does 45 degrees phase shift with every step you add (45, 90, 135, 180).

I'll send you conversion table what you can use to calculate crossover correctly.

And here is the conversion table:

Oops, I did write wrong way into this sheet.
In Devialet and In real life should be opposite.