Join Date: Dec 2000
Location: Chicagoland, IL.
A damaged or blown speaker will sound very thin, buzzy, or not at all. It depends on what goes. Sometimes the voice coil will seperate from the cone causing a thin rattly sound. If the coil burns out, you won't hear anything.
The problem you describe could be a couple different things. Damaged cone, something rattling around behind the speaker against the cone, something loose inside the cab or something in the room may be vibrating at those specific freqs.
Make sure there are no loose items such as jacks, hardware, or handles in or on the cab that would cause that.