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
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