There is breakin with some footers. Depends on material makeup, geometry of device and the mass of the unit sitting atop the footer. Some components will over a period of time develop a vibrational pattern that will exist even when a highly resolute footer or shelf is replaced by a different footer or shelf. The speaker the chassis or the musical instrument is much like a capacitor in that its material makeup is a storage device with a memory of signals that pass thru. I have recorded this process happen and was shocked and dismayed at first, soon to be excited by the understanding of why it happened. Tom