I've posed a similar question elsewhere here:
https://www.audiosciencereview.com/...ge-speakers-how-to-measure.16976/#post-550937
The problem is not doing it. Earl Geddes recommended running mains full range in his initial investigations into multi-subs.
And the problem is not bass depth. Mult-sub configurations do not need every sub to be able to play loud below 20Hz. The room response benefit is higher up in the modal region.
So, in my case, I have a sub capable of 20Hz bass at the levels I listen to (Rythmik) and I have speakers capable of playing flat to 35Hz at the levels I listen to.
The sticking point is bass management, measurement and EQ.
My amp (Anthem) normally has very good bass management and excellent EQ.
But it does not have a setting that allows me to run my mains full range and my sub to overlap (Double Bass or LFE+ on some prepros).
Fortunately, my Rythmik sub does thanks to seperate LFE and line inputs, plus the ability to adjust sub low pass when using the line inputs.
So I can run three bass sources in different positions, and adjust volume and phase.
But the problem is objectively getting it right, and then EQing to taste.
I normally measure speakers and subs individually, and then EQ each.
A multi-sub approach means you have measure everything together. I use REW which means a L+R setting.
And when doing such a measurement the overall response is indeed better than a simple 80Hz xover to the sub without any EQ.
But it is most definitely not as good as that same 80Hz crossover to the sub with Anthem's ARC EQ in action. Ditto, measuring each individual speaker 'full-range ' (ie main plus sub).
My room correction doesn't work on the multi-bass sources because it measures one source at a time.
I could theoretically add a MiniDSP into the chain to EQ the combined response after some REW measurements.
But it is added complication.
And I'm still not sure how to check whether doing this would be an actual improvement over Room EQ.
Mind you, I should probably have qualified all this by saying I'm trying to perfect one listening spot.
Mine.
My wife doesn't give a hoot what things sound like at the other end of the couch.