Taking off out of LHR a few years ago in a 747/200 we had a very large bang at Vr Tower advised they had seen flames out of the number 2 engine....It was a "Compressor stall... " continued the 8 hr flt... A DC10 went off the end due to high speed reject in YVR ,I believe was a compressor stall... Just a thought... The bang gets your attention.... I have had simulator instructors try to give a similar situation by banging the wall of the sim but not the same effect.