The rationale is the development of the new SR-007A (SR-007MK2) Earspeaker was to provide deep powerful sound previously unobtainable in Earspeakers. STAX engineers developed a unique new electrode structure. Visible through the outer case, gold plated on the outer edge this new electrode has no holes unlike conventional STAX Earspeakers and thus provides an increases diaphragm vibration area allowing for rich and powerful sound yet retaining all the delicacy STAX is famous for.Rigid Metal HouseTo maintain clear distortion free sound it is most