8-10 HZ?? Being that those frequencies are well below the threshold of most systems, how are you noticing them? What is your recording system; digital, analogue? Can you not simply use a high pass filter to remove them? Is the Shure microphone you are using for comparison a condenser or a dynamic? The frequencies you mention can be generated by resonance in an air conditioning systems ductwork. Is it possible that your'e seeing that on your waveforms. I assume your seeing them on the waveforms because you're certainly not hearing them unless you have one amazing speaker system. Even then, your ears can't perceive frequencies that low. Feel them in your bones maybe, but not hear them.....olduncledino