There is one device that can configure them for you in the frequency domain and in the time domain with the push of a button: DSpeaker 8033, up to 4 subs. I sold mine when I bought an AVR that could configure 4 subs but regret that I did now. The DSpeaker is better.
How many subs?
I got my room analysed by an acoustic engineer.
3 subs - 2 with delays.
Maybe I did not have the gain set right for each sub?
The pressure in the room was overwhelming. Opening the door was a relief.
One sub - front left - the one with no delay in the design seemed really good.
But I got hungry for more - so I tried 2 subs.
Does anyone have experience with using a multi-sub setup using delays?