Figures 63 and 65 show a response that is less dominated by room modes.
Unless I'm missing something, that pair of graphs seem to show longer
ringing in the "corrected" version.
But the one thing none of those graphs show - and this is a recurring theme with papers such as this - is what happens an inch away, and two inches away, etc. I already said I agree that DRC can reduce ringing at the single point in space the measuring microphone is placed. But the reduction will not be useful in practice
unless it's valid for an area at least a few cubic feet in size. And that is where every one of these DSP systems fails.
I agree that a playback system should have no modal ringing in the bass range but this is not necessarily the first problem you should attack for every room and every budget.
Okay, let's discuss. Again, I'll go first.
IMO, the most damaging bass problems are between around 80 and 300 Hz. This encompasses the primary "fullness" and "clarity" ranges of bass instruments. This is not to discount problems below 80 Hz, because it's all important. But most music has little energy at those very low frequencies, and most playback systems cannot go much lower than that anyway. Note I said "music" and not "home theater" where LF sound effects are important. But even in that case, if an explosion is a little extra loud, or lingers a little longer, not a lot of damage is done.
I don't know if you agree with the above, but for now I'll assume you do. So now we're down to what's the best way to handle bass problems above 80 Hz. It's clear to me that bass traps are superior to DSP in every single way because they can improve nulls, and ringing, and the improvement is valid over the entire room. None of which DSP can achieve.
As for expense, you can buy very expensive bass traps, medium price bass traps, cheap bass traps, and even DIY your own bass traps for literally a few bucks each. The cheapest bass traps may not be as effective or as nice looking as the more expensive ones, but they will still be highly effective. If you look through the various "How I made my traps" threads in the Low End section here at Gearslutz you will find dozens upon dozens of people who made huge
improvements to their rooms for $300 or even less by building their own bass traps.
Now, tell me again, how much does that IK/Multimedia plug-in cost?