window

I'm wondering how to add a window to and enclosure. I'm considering 3/4" thick plexiglass, but is plexiglass acoustically dead enough for enclosures? or is there a better material? also tips on how to get it flush with the side of the enclosure would be great;)

Hey everbody im new here and had a question about my speaker system, I have 4 W12GTi MkII's and whenever i roll down my passenger side window they become twice as loud. They do not get louder if i roll down my drivers side window or open both doors, only if i roll down that specific window will...