Hey guys, I've got an old Fender bassman60 amp and it has performed well for me for a good while. It has a 1x15 speaker. Anyways, I was playing at church this morning and suddenly noticed this wierd chorus type modulation whenever I played in the higher register. At first I thought it was my chorus pedal malfunctioning or something to I took it out between songs and just played straight into the input. Still the same problem. I can't figure out what it is. Could it be my speaker is about to blow or what???