Next step is not necessarily the one you might think of. The acoustics expert would treat first reflections on side, front and rear walls as a matter of course, but the next treatment I’d recommend is adding a DaaD 3 at the middle of the wall behind the loudspeakers. If possible, make that two. The only way I can describe this is an elimination of crosstalk between the loudspeakers, which makes the placement of sounds within the soundstage far more accurate and precise. Funnily enough, those of a traditional ‘flat earth’ persuasion who think imaging is the stuff of audiophile nonsense (who are also seemingly the most apt to dismiss room treatment too) should try this DaaD 3 between the speakers and nothing else, especially if you use boundary loudspeakers. It will make your wall of sound bigger!
Finally, the DaaD 2 or Eco DaaDs are used in the first reflection points act to tidy up the precision of the sound in general, snapping the sound into some kind of tight focus that is difficult to achieve without first reflection diffusion. The Eco DaaD’s one great advantage over its rivals may be its biggest disadvantage; because it is narrow it looks good, but because it is narrow, it needs to be very carefully positioned for full effect.
The Acustica Applicata system is expensive by room treatment standards, but it’s also one of the few that needn’t be a fixed install (Eco DaaDs excepted) and has a built in fail-safe for overpowering the room – if you have an Acropolis in the listening space, you’ve gone too far!