Occurrence in which a speaker driver continues moving after the amplifier signal stops moving the voice coil back through the magnetic field and creating its own voltage which flows back to the amplifier and creates a flopping effect in the speaker driver. This effect creates sound distortions that are very unpleasing. n order to stop back-EMF, the amplifier driving the speaker must have a high damping factor. The amplifier’s damping factor measures its ability to stop the speaker driver at a designated point. The damping factor is similar to the breaks on a car. A high damping factor equates to a car with excellent brakes. To stop a car travelling 60 miles per hour might take 200 feet for an average car. A car with great brakes might stop instead in 120 feet. This car’s brakes could be said to have a high damping factor because they can quickly control to motion of the car. Similarly, an amplifier with a high damping factor can cease the motion of the speaker driver quickly and properly thus minimizing back-EMF or the voltage transferred back from the speaker to the amplifier due to driver flop.