Room acoustics

OK, for a kick off: measurement. To measure and interpret in-room response, you need a measurement microphone and a system to generate test signals, to record the response, and visualize those data in a graph. These days, that can all be done with a free software package: Room Equalization Wizard (REW), for Windows, OS or Linux. All you need in addition to a computer and this software is a calibrated measurement microphone. Personally I use the microphone that came with my Antimode 8033 room eq (plus its MicAmp), but for most people the calibrated UMIK-1 usb microphone is their best bet, at $75.

The result is likely to horrify you, and serves to underscore the importance of speakers and of optimizing their in-room response. It is not unusual to measure in-room peaks and dips of +/- 10 dB. Compare that to the peaks and dips of good electronics - usally +/- 0.2 dB over much or all of the audible frequency range. That 0.2 dB limit is important because it represents about the smallest level difference that humans can recognize. So the peaks and dips in listening rooms are many times larger than that. A significant part of those unwanted deviations from a flat frequency response originates in the room itself, and not in the speakers. Good speakers are not nearly as flat as good electronics, but usually manage to stay within +/- 3 dB for much of the full range of human hearing. Usually only the bass region is much lower. Compared to good electronics, +/- 3 dB is still not very good, but far better than their real life performance in an actual listening room. So the challenge is to get them as close as possible to their best performance in an anechoic room, or free field outside in the open air.

Your big problem will be that the measurements will be way off in the bass, and considered by the measurement formulas/methods to be impossible to navigate and thus.... not relevant. Even your measurement systems, a weighting, c weighting, ...they all ignore the bass. Bass is not looked at in professional environments and professional scenarios.

"Since the ear is insensitive to 500hz on down, we’re not going to measure it!"
http://www.noisemeters.ca/help/faq/frequency-weighting.asp
Seriously.

Yet your bass to midbass will be the the source of the vast majority of your room issues. As in: the heart of the matter.

the mid-high parts they talk about dealing with, anyone can fix those with a small bit of internet research. the odd throw rug, some simple diffusion, common knowledge stuff.

Bass traps, the vast majority of them, barely do much of anything at all. We hear the small bits they do and we take what we can get from them, happy for any minor improvement.

Going into a commercial box or Imax theater and listening to the surround systems in them is a horror show. Awful sound and awful acoustics. These are supposedly professionally done systems. It illustrates how little even the pros know about bass and midbass and how to tame it. Ultimately, billions of dollars involved in getting it right, and they can’t get it done.