There are three main benefits to going dual:
1. Improved (flatter) frequency response at MLP due to fewer/smaller nulls
2. Higher SPL output capability
3. Reduction/elimination of subwoofer localisation
I went with dual subs for the first time last year in pursuit of #1 but the improvement in SQ from #3 alone would have been worth the upgrade which really surprised me. IMO #2 is the least important.
Also, just because you have dual subs it doesn't mean that you'll get a more even response - for that to happen you have to put them in the right locations. For example, this is what dual subs do in my room if they're both up front like most people have them (this is a REW prediction but the measurement is very similar).
View attachment 1667965
To get rid of that massive null from 35-55Hz the subs have to be positioned in the rear corners. Add a MiniDSP and the FR is now extremely flat (+/-1dB) from 18-80Hz.
Wow you dive into the science like a pro.
Fair enough. But if you go dual then surely it has to be same driver and type of subwoofer/size and so on right?