Curtains to cover bass traps

I am using Gik bass traps at 4 corners which are quite ugly. I am thinking of covering them with narrow curtains at the corner. I suppose bass freq. pass thru readily and should not change the perfomance of the traps. The mids and high would be affected but surface area is not large so effects should be minimal.

Am I correct in this? Any particular brand or fabric to recommend or aviod