Rub&Buzz (R&B) describes the audible imperfections and production defects of loudspeakers and transducers thatcan occur during the manufacturing process.
R&B can be caused by:
Rubbing coil
Lead wire touching the cone
Membrane misplacement
Moving coil stuck
Excess glue
Air leaks
Tumbling moving coils
R&B is fairly easy to hear but extremely difficult to measure