How U determine first and second reflection points

Between my post, Snofun3's post and Fmpnd's post, you have the same method nicely described by three different people. Pick one and have fun.

I found it easier to use a small mirror if I put a lamp (no shade) at the center of the speaker, then, as above, move the mirror until you "see the light".

Other choice is to sketch your room (to scale) and find the reflection point on the drawing (where the "angle in" equals the "angle out"--in other words, the angle the line from the center of the speaker to the wall makes is equal to the line from that same point to the listening position). Lamp is much easier...

I have not worried about 2nd reflections

So, each of the left and right walls will have 2 relection poinsts - one from right speaker and one from left speaker?

Or, each wall will have first reflection point from the speaker on the same side and the reflection of the speaker on the other side is considered second refection point?

seems like slight difference in definiton of first and second reflection point by Tvad and Fmpnd.

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.