Excuse the noob question, but is mounting screw hole spacing standard or universal in guitar speakers? Will I need to drill if I swap out Celestions for Eminence? Thanks for any info!
They're not universal, but if you put both speakers on a paper sheet, you'll find that around 11 & 5/8" is the center to center diameter of a Celestion/Scumback mounting screw setup.
Keep in mind, though, that frames are not universally the same diameter. I find that I have to widen some speaker holes because they're not wide enough for a front mount setup.
In other words, yes, they should be a universal bolt pattern, but the hole cut for the frame in the baffle board needs to be checked to see if it fits your speaker.