Room Acoustics: Where to place the squares?

For the OP and @4krowme I have some brands:

GIK Acoustics - Great performing, not the cheapest, but high value

ATS Acoustics - Even cheaper than GIK, also good but GIK has some models that are exceptional

amcoustics.com - Great resource for learning about room modes and room acoustics.

The bottom left of the Amcoustics page has a calculator for panels.

But to cut down the early reflections is another matter.

My point is, if you don’t have control over the room decay you won’t notice first reflection point absorption. I’ve treated several rooms, and never have I heard a big improvement by treating first reflection points alone. Only once the room was better treated did those panels suddenly become worthwhile. We pay too much attention to first reflection points, IMHO. It’s not, alone, going to do much good.

How many and how big??

Of course people will advise you to put them at 1st reflection points but honestly I find that alone this is never enough.  You need to have a critical mass of room treatment before you get a noticeable benefit IMHO.

Spread it around!