I recently finished remodeling my family room and am having trouble with bass FR. I have a deep null at 40hz and am not able to move the sub. I'm using a parametric eq but really want to build a couple bass traps to flatten out the FR. Can anyone tell me what can be built in the way of a wall mount trap that significantly absorbs frequencies that low? Most that I see don't give much info below 65hz. I like the examples from Ethan Winer but didn't know if they would be effective at 40hz. Thanks in advance, Eric.