Trying to figure this out.... This guys bass drums sound exactly like a car with engine knock problems.... I'm guessing maybe he's using drum triggers and you can hear the actual sound of the real bass drums along with the artificial. Is that the reason? http://www.youtube.com/watch?v=4sRN-IG8Jvs&list=UUQWh0ZNBdCNIJeCkX12-CGQ&index=5