Hopefully, through positioning, you can reduce the problem to a narrow range of bass frequencies (ie. 50Hz-->60Hz) If it still bothers you, it might be necessary to change out the speakers for ones that roll off below about 60 Hz or use a parametric equalizer or low pass filter.
You may need a sound level meter, a tripod and some test tones (on a CD or otherwise) to fix these issues.
You may need a sound level meter, a tripod and some test tones (on a CD or otherwise) to fix these issues.