Windows behind the speakers - yes or no?

[silva741]

I'm in the process of designing from scratch a room which will work as home theater, stereo listening room, and ocasionally, living room. I was under the impression that the wall behind the front speakers had to be as massive and thick as possible, but saw a few opinions stating the opposite, since the speakers send the sound forward, and the worry should be with the side walls and primary reflectons.

Can someone please shed some light on this subject?

Just as example, here's a picture I came across, precisely of what is a very beautiful room with big windows behind the speakers.