Single vs. Dual Subs


It's common wisdom that dual or multiple subs help smooth out bass response in different spots in the room, but what about for a dedicated listening room with a fixed single listening position? What do two subs add to the music presentation that a single dialed in sub is missing provided that single sub is dialed in perfectly for the listening position?
Caveat: not interested in the SWARM method or multiple subs at the moment, strictly comparing single to dual subs
divertiti
Indeed, the multiple sub solution outlined by Toole and on which the Distributed Bass Array approach is based is a game-changer. Multiple subs distributed asymmetrically around the room effectively minimizes the problem of bass modes. Then when the subs and everything else are isolated on Townshend Podiums and Pods this virtually eliminates another major source of room mode excitation. The combination of the two is stunning. It takes a huge amount of bass traps and other room treatments to match what isolation and DBA can achieve.  

Then if on top of all that you go to Townshend F1 cables, these eliminate yet another source of harmonic resonance. 

The old-school approach of EQ and room treatment really is old school. There are much better solutions available. People are catching on. Good to see.
Miller +1on subwoofer isolation.

My subs have been supported on foam padded dollies with extra soft rubber wheels for many years now.
After a move and before a permanent system setup we had our single 18" sub sitting on some folded moving blankets. We noticed how much less the low frequency excited the structure while still providing deep bass.

When we purchased our current 12" subs ten years ago I connected the 12s and the 18" with RS-232 cable and the home theaters 15" Super Nova with L/R interconnects. Effectively creating what's now called a swarm which did indeed eliminate all the rooms bass modes.

We noticed little if any sonic advantage between Cardas Golden Reference XLR to Canare XLR.
On the other hand when I applied the four subwoofers with fourteen parameters of the subwoofers Room Optimization the improvement was stunning while adding the flexibility of remote controlled preset equalization. 

I'm very interested in the "much better solutions available" you mentioned?
@m-db, The much better solution is using digital bass management which includes room control and digital crossovers which are far better than analog crossovers. From less to more expensive you have MiniDSP, DEQX, Anthem and Trinnov. Check them out. If you are a person who is stuck on analog only just forget about it, my mistake. 
I'm running a pair of Tekton 4-10 bass towers & am very pleased. Prior to this, I was using a single REL sub. The bass towers improved not only bass (as expected) but also soundstage width, depth, instrument separation, & top end clarity. A very nice improvement top to bottom. I have these in a dedicated room that is around 15' square.