This is common with these types of speaker systems. The Harmon Kardon Aura has built-in equalization and protection circuitry, but it can only do so much. Heavy bass can sometimes overwhelm these circuits and the small bass speaker. You can try turning down the bass settings, either in the Aura itself or through the source you’re playing the music with. If you still have distortion regardless of your tone settings, then there may be damage to the bass speaker in your Aura. This can happen over time if the speaker is overdriven. Replacing the bass speaker is possible, but it’s not an easy task since the Aura isn’t designed to be taken apart very easily.