Blown Monitors Query

Question about blown monitors:

Why do we get speaker rattle when playing a bass synth on its own, but none when playing a track off youtube? I've even found a jungle tune where there's a sinewave bass and little else apart from some light percussion... but still no rattling/distortion. IT DOTH BOGGLES THY MIND!

Are you testing the same frequencies? It could be something caused by a resonant frequency or you might have a tear in your cone in a peculiar spot.

I'm testing the same frequencies. I think because of the other instruments (however little) affecting the movement of the speaker cone, the cone rattles less?