After giving my new sub a few weeks for break-in, I recently did my calibration using the Avia DVD. During the frequency sweep section, I noticed that my rear wall vibrates violently at 35hz and below. (This wall was added when the lower level of my house was finished off). What would be some good choices to alleviate this problem. I've heard of people using patio stones at the bottom to stiffen it up. Would bass traps in the rear portion of my room do anything to help. Picture frames on this wall were actually bouncing 3/8" or more. Any help would be appreciated. TIA!