how can I make the back wall transparent?

If this is the wrong place for this topic please move it

My listening room is 11.5 x 15 and my speakers are 3.5 ft from the back wall.

I have spent considerable effort tweaking stuff, to the point where the system sounds very spacious and deep, BUT it still does not sound as spacious as systems with 6-8 ft of free space behind the speakers.

Is there any aesthetically pleasing wall treatment available that would give me that depth without moving the speakers

Taking the wall down is not an option:-)
Those days are long gone, but no bug could survive the music we played back then. I do miss the ability to sleep on the ceiling.

What is the final position of your speakers relative to the wall behind them and the side walls?

Perhaps I should take care of my exterminations with trying to listening to your band Wolf. Can you share?