Help! Buzzing sound from dustcap

[angsuman]

I have a dayton 10 inch mkIII subwoofer. I just finished my subwoofer and noticed a buzz coming from the dustcap. its the same tone buzz that doesn't change. It seems to be present around 60-80hz. It is rather easy to hear at low volumes or when you put your head near the subwoofer.

I'm curious does anyone know what this buzz could be coming from?

 

[Volenti]

Could be a number of things, loose dustcap, little slag of glue rattling around inside the dust cap, some voicecoil windings hanging off the end of the former, voicecoil rubbing in the gap, ect.