Not enough. The only chance of building a reasonably inaudible housing is stone or concrete, or nothing;-)
A knock test is enough;-) Knock on your highly braced non-cardboard enclosure;-) Then you can hear the character that resonates and colors your music as well as diffuses the image;-)
A knock test is enough;-) Knock on your highly braced non-cardboard enclosure;-) Then you can hear the character that resonates and colors your music as well as diffuses the image;-)