FWIW, I tried the DIY approach to making absorption panels and then I tried GIK's products. Considering the time expended and cost of purchasing quality materials to make DIY panels of equal quality to GIK's, I can't imagine why anyone would bother unless you just enjoy experimenting to occupy your time. Their products have an outstanding price/benefit ratio. They will also give you guidance on the best products for your project.
You asked if the expanse of television glass affects your audio quality. Yes, big time. Getting rid of the tv between my speakers was one of the best things I ever did. Unfortunately, many of us have to compromise and combine AV and audio in one location. In my past experience, acoustic panels in front of the tv help some but don't entirely ameliorate the bad effects of the tv.
You asked if the expanse of television glass affects your audio quality. Yes, big time. Getting rid of the tv between my speakers was one of the best things I ever did. Unfortunately, many of us have to compromise and combine AV and audio in one location. In my past experience, acoustic panels in front of the tv help some but don't entirely ameliorate the bad effects of the tv.