I have a Schroeder 21012 which has recently started producing a buzzing sound. The thing is it only does it between C and E flat(lowest c..3rd fret A string up to 6th fret, 8th fret E string etc..). I checked this thread and tried some of the simpler things mentioned there but no luck. My instincts first told me it was blown but there seems to be no physical damage to the cone. I also was unable to find anything loose inside. That said, I'm kind of a dummy when it comes to this stuff so I don't always know what I'm looking for. I'm using a Modulus Q6 and have tried setting my EQ on both my bass and amp head flat to no avail. Any ideas?