How U determine first and second reflection points

Fmpnd - Ya snooze you lose guy. Sorta germain to this thread - mirro, mirror on the wall, who's the smartest....
;-)
No excuses man.
What were you supposed to be doing anyway? I'm "Working from Home".

Better yet - YOU sit at your normal listening position, have someone else slide a large mirror (One of those back-of-the-bathroom door mirrors works well) along the walls. When you see the reflection of the speaker in the mirror, that's your first reflection point, and where you need room treatments. Auralex foam, available at Guitar Center, or some other of the same type stuff is fully adequate.
Note that you should do the same on the ceiling too, as the reflections are just as strong.
Your speaker's imaging will thank for for the effort.

Eandylee - Correct, however there are actually more if you take the floor and ceiling into account, and don't discount them as they are quite significant. It's easy to put a rug on the floor - a bit more difficult on the ceiling.

Ah, C5150 - yes, in fact sound travels in straight lines - it's not real good at going around corners. Try having someone else stand in front of your speakers - see what I mean. Sound = straight line.
Reflections of straight lines = standing waves - not a good thing. Mirrors show you where they occur.
Nevermind, just go enjoy your instrument.

Oh - Zargon has a good point. The rear reflections are probably worse than from the sides. I've deadened both walls enough to tame that form of standing wave.

Tvad, I think we'd exhausted the subject anyway.

Well Cdc, If you want to see that first reflecting point on a permanent basis I suppose that's useful - why else would you want a mirror on the ceiling?

Not saying that at all - sound reflects in staight lines (many, many, many straight lines - it does not zoom around corners, honest), and when the waves bounce back they cancel each other out at a certain place (standing waves). The way to stop that is to not allow them to reflect back.
Oh never mind, everyone else seems to understand just fine...Yes the earth is flat, and intelligent design is a science - happy now?