Cool, thanks. I asked exactly this question to the dirac live helpdesk. Let's see of they answer! If it is like you say I will most likely buy another sub.I recall watching his video - not sure if this one. My understanding is that you need to set up Dirac first (including crossovers), and then go to ART setup which is different screen and methodology.
Getting rid of time decay is most difficult thing in the bizz as room treatments for sub 80hz range are military grade in terms of looks, size and price. Double bass arrays are minimum 4 subs and will have strict placing requirements so in most cases you end up with primitive aka not fully functioning DBA. This is where ART is supposedly going to excel and for example do the same thing with 2 subs and less placing constraints. Time decay will of course improve the frequency response as the lingering bass will no longer be recorded as peak as it is not lingering. But that is where the magic stops.
ART will not really fill in your null at e.g. 50hz (if DLBC was not able to or placement of the subs) as for that it would need to play a really loud signal from the supporting speakers, which is contrary to the settings provided and instructions to keep the signal low and far from obviously audible. For the core frequency response you will be limited to what you got and traditional DLBC approach.
As noted, ART information comes in bits and peaces. Then you try to patch them together best you can. Surprised that more advanced users and beta testers have so little to say though.