Which of the following can cause resonance in an audio system's sheet metal?

Resonance in an audio system's sheet metal can primarily be caused by loudspeaker vibrations. When loudspeakers generate sound, they create vibrations that travel through the structure to which they are mounted. If certain frequencies correspond to the natural frequency of the metal enclosure or components, it can lead to a phenomenon known as resonance. This occurs when the vibrations amplify due to constructive interference, resulting in unwanted sound distortions or a buzzing noise.

While other factors such as improper installation or power fluctuations might affect overall audio performance, they do not directly lead to the resonance of the sheet metal. Speaker wire quality primarily impacts the signal transmission and overall sound clarity, but it does not contribute to the mechanical vibrations that can resonate within metal structures. Therefore, loudspeaker vibrations are the most direct cause of resonance in this context.