I have an issue with my sound system. I get spontaneous loud bass notes over the ambient music. They occur randomly in sets of two three and four note bursts. No apparent triggering event.
My best guess–and that’s all it is–is that you have a short in the audio system somewhere. The “thump” of a short can sound like a bass note. Another possibility is that you’re simply pushing the audio system too hard but we’ll leave that for now.