The kind of trouble that most commonly found on Alienware M15x speaker is sound crackling. The problem is suspected to be caused by a poor power distribution, or the power is interrupting the audio output. When power is supplied through the mains, it is constantly feeding a current through, whereas on battery, the exact amount of power at any one time is given. This constant supply of power is believed to affect the audio.
However, there is no time for keeping on being frustrated should you be on this kind of trouble. There must be a certain way to overcome it. Say you have a M15X with this problem of crackling, you can end the problem by simply turning on the AlienwareFX should you run on AC power, but do not set it to dim. And if you run on battery, you can choose to turn the AlienwareFX either on or off. This simple step was proven in some cases to have worked with or without WASAPI.