...Not everyone will have to go to this extent to get a good sounding room, but it certainly helps. Particularly in a space that's this narrow. ...

Wow, who's space is that?

I was headed in that direction and I decided to just reverse course and start with minimal.  Corner bass traps, first reflections and a ceiling cloud.

Those skyline diffusors look sick though.

EDIT:
Are those (helmholtz?) resonators below the skyline diffusors?

Also, that space probably wasn't that narrow before all the treatment, what are those, like 8"+ traps at the sides of the speakers?  Is that for sbir/room modes/both?

Marv, we come from the same background I believe. I was into speakers for something like 10 years before I went seriously into headphones. I don't pretend to know so much but at least I did design several speakers (some really terrible souding as I recollect) while doing an internship at a small high end audio maker. I work daily on problems involving room acoustics. From this, there's one sure thing: it's a hell lot harder to make a speaker system sound right and there are so many compromises to make in the design.

"Using the room to your advantage" by loading the speaker in the corner. That's another load of bs, you're just exciting the first modes of the room even more strongly, which is required here to get some impression of bass out of typical full range horn loaded drivers. I can't stand full range drivers, the tonal colorations (you invariably get breakup modes right where it hurts (1-5kHz) range. You might like that better than headphones, I think it's just the change of flavor that is attracting you and it will sooner or later get old.

A fairly typical room response plot from a smallish room. Again, 10dB or more is nothing out of the ordinary. In the bass region there are MASSIVE swings here, closer to 25dB.

Yeah. Small rooms are always a problem. Best to place speakers where the room isn't fully enclosed. This requires space of course and would be difficult for most in Europe and Asia where there is higher population density and folks living in tighter living spaces. My advice for people with small enclosed rooms is to use headphones while checking out the latest FOTM portable DAC/amps, or commit suicide, unless they are willing to work really hard to make speakers work.

Bass is always problematic no matter what. However, I would argue that 1/3 - 1/6 octave smoothing be applied as this would be more representative of human hearing acuity. It's impossible for people to detect such sharp dips, i.e. 900, 2k, 6k, etc. with music.

A fairly typical room response plot from a smallish room. Again, 10dB or more is nothing out of the ordinary. In the bass region there are MASSIVE swings here, closer to 25dB.

Yep. The modal region is the one place where headphones are usually far superior to speakers in room. However, one can fix that by using multiple subwoofers and a suitable controller. Then it's possible to have the bass look like this at the listening position:



AND have very low mean spatial variation (MSV, which is what all of the Welti/Devantier work on multisubs at Harman is really about).

What that kind of bass performance sounds like is superior top-to-bottom coherence, slam (which is really an integration thing, not an extension thing or an output thing), and much greater variability in the size of the perceived space. A piano in a living room sounds like a piano in a living room sounds like a piano in a small room. An orchestra (played at realistic volume, at least) sounds like its playing in a large hall.

Any home audio system that does not employ multiple subwoofers and suitable EQ based on in-situ measurements is a low-fidelity system. Period. Doesn't matter if the speakers are some cheap full-range deal or TAD Model Ones.

PS: That room above would work much better, IMO, with very narrow-directivity speakers cross-fired (i.e. aimed to cross a bit ahead of the listening position). That would eliminate the need for the sidewall treatments, and likely increase perceived spaciousness without compromising imaging. Nice job of removing diffractive elements from around the speakers, though.

I do plan on multiple subs. DCX2496 is great as a subwoofer x-over. You can program in time delay and phase to align with your sitting position. Once it's dialed in, it's really scary how good it is.

BTW, I love EQ with the tools available today. Not so much true 10 years ago.