Does the first reflection point actually matter??

The one issue missing from this discussion is your impression of acoustic treatment at first reflection points completely depends on how wide a dispersion speaker you actually use.  A speaker that narrows with frequency, say a horn, will send less info to the side walls as frequency increases.  A ribbon or any planar device will also do this but it can depend on what frequency the planar portion of the speaker is working in. 

So imagine a ribbon working at 3K and above.  You wont get as much energy at 3K and above on first reflection points as they get fairly narrow even at 3K and get even narrower as you get to 10K and above.  This is easily demonstrated by rotating the speaker until it almost faces the side walls, you'll hear bunch of splash as you get more energy on it.  Also the wall material matters- glass is very different frequency emphasis than wood.   There are many different types of absorbers- some work well at HF, and some work better at mids and some are built to be LF absorbers with membranes. 

SO there is no universal answer to this other than to say if you have a wide dispersion speaker, the first reflection point absorption is critical to improving image.   If you have a narrow dispersion speaker you may not hear much difference.  Also you need to buy real absorbers like GIK, or make them, I like the 4 inch thick ones, they absorb more for the same wall space.   

Brad 

If I ask someone with Floyd Toole level knowledge of loudspeaker-in-room acoustics (which I can with Billy Woodman at ATC),  he would tell me that consistent spectral content of direct vs reflections is the key to imaging.  If the reflections look very similar in spectral content to the direct sound it will image well.  That's why he builds wide dispersion loudspeakers. Narrow dispersion loudspeakers, having different spectral content off axis than on axis, sends spectral energy that does NOT sound like the direct sound on reflection "zones" (love this word Duke, well done).  Its all about the sum of these two complex sources of (direct vs reflected) energy at your ears, because when they combine with each other they partially cancel or completely cancel each other.   Longer path = longer time= phase shift.   This is the idea of nearfeild monitoring in studios, reduce the amount of reflected energy by sitting closer and moving the speakers further from the walls (smaller triangle).   Now you can hear more of your monitor and less of the room.  Engineers use this idea to help them get a more consistent sound in the different rooms they work in without changing speakers, using EQ or DSP (all of which adds another "veil" to the direct sound).  I remember seeing Kevin Shirley mixing about 2 feet from his speakers which were about 2 feet apart.   Not so much "room sound" in such a set up.

Brad    

I think many of the mysteries discussed in this thread make it difficult to grasp the unifying issue.  Different rooms and different speakers, its extremely complex behavior.  ( I swear acoustics is a black art) Is it the speaker or the room?  Erik talks about how he doesn't hear much difference with absorption at first reflection zones.  Another poster says absorption at first reflection zones is HUGE, big difference.  How could they both be true?    

I am suspecting the common issue between these two ideas is the speaker dispersion: the wide dispersion having a stronger effect on first reflections, the narrower having less impact on reflection points.  It is quite possible we do not know what the mid and/or tweeter dispersion of our speakers really is.  If we don't know, we could attribute a lot of audible results to things that may be unrelated.  The specs we are given don't come close to revealing this super important info. 

Brad