What process did you use to integrate multiple subwoofers for 2 channel listening?

So in my case, FWIW, I’ve been able to get the sound I want with a sub and good but not full range small monitors (KEF ls50 meta) simply by getting the mains setup optimally first, then using decibel app on iphone and streaming white noise to get the sub to visibly fill in the missing lowest octave. Only three controls to play with on one sub, a Klipsch sw308: level, low pass cutoff, and phase. I eyeballed it with the meter app, then sat down with some music to fine tune the sub. It’s perfect to my ears now! Took about 30 minutes to get it dialed in (sub controls are accessible from main listening position). Discovered I had not landed anywhere near the right level and settings for the sub by ear alone. Low pass cutoff way too high and level way too low.

It helped that that room is thin dense carpet pad over solid concrete foundation. No floor resonance issues there like I have upstairs to deal with. If you have those, tackle those directly with isolation pads or equivalent under speakers.

Of course all rooms and ears are different. Also experiments are how you learn. I learned never make these things any harder or more complex than necessary to deliver results that are technically good but more important pleasing to the listener.

NExt step would be DSP just to see what happens and if worth it, but I am at a good place now so not much incentive to dabble more than needed at present. Maybe someday when I retire.

@mapman 

It helped that that room is thin dense carpet pad over solid concrete foundation. No floor resonance issues there like I have upstairs to deal with. If you have those, tackle those directly with isolation pads or equivalent under speakers.

I'm on concrete, too. 2/4 walls are brick. Not a symmetrical room but not much resonance.

@gosta  The guys on the hifi podcast just described a guy who spent 150k on a room for listening using treatments, and other tools and it still has problems. 

My steps on bass integration/room Eq. 

1st do appropriate room treatments, *this is the foundation for all that follows.
 2nd add multiple subs 2/3/or more.
 3rd add a crossover to eliminate mains from the sub                              
 4th integrate DSP in the Sub range.

Took my room size and layout out of the equation.





              

See my posts on bass and room treatment. A huge amount of boomy bass was eliminated with vibration control- Townshend Podiums and Pods- and a lot of the rest went away with F1 cables. Yes wire contributes to resonance problems.   

If I had gone the traditional tube traps first approach I would now be struggling to restore that which was being unnecessarily removed with expensive bulky tube traps. 

It's a new millennium, boys. One sub is out, DBA is in. Panels are passe, HFT are hot. Podiums trump traps. Etc, etc.