House the helicopter effect is neither nor.. the drivers extend continuously in rapid succession - as if a the sound of a helicopter was being sent to the drivers... sorry, it's the only example I can come up with. and it happens at medium to high volume levels when there is a big boom (like when a Transformer lands after jumping in the air)...
The humming/vibration happens when there is a rumble... like when the cars are driving by in Tallegeda Nights...
only two things can stop it once either starts:
1- I cut power to the sub
2- I turn the crossover dial on the sub down until it stops.
