I seem to recall somebody saying he/she sent a Grado in for repair and was quoted a fee of $100. I don't know if I'm remembering this correctly but Grado ended up charging this person nothing. Obviously, expect the worst; hope for the best.
The coil is the "coil" of copper wire that spools around the magnet. Together with the magnet, it creates the magnetic field that causes the diaphragm to shake back and forth. Grado uses flat-coil wire. There's a notch cut into outer ridges of the face of the magnet that rings it. The coil slides right into this notch. Wires from the coil are attached to the diaphragm like battery cables, albeit with glue.
Under certain circumstances, the coil can slide out of its notch around the battery. It doesn't happen often. You could own your headphone for a lifetime and never have this happen. However, a combination of conditions - the right amount of humidity (or lack of it), gravity (particularly if the headphones have been burned-in with shells placed diaphragm-down), and/or excessive volume. I've had the coil slip out while removing the driver assembly from its plastic cage. Any tug at the diaphragm can become a tug upon the coil, pulling it from around the magnet. If the previous owner didn't drop the headphone down a flight of stairs or take it through a car wash, the most likely culprit is either an unfortunate mishap stemming from burn-in procedures or slipshod assembly. It's possible that when the coil was originally inserted, it wasn't aptly inserted. It doesn't take glue to hold the coil in, but if the coil were placed improperly during assembly (though not improperly enough to cause an immediate problem), you could get slip-out.
There's are better and worse fixes for this problem. Essentially, the coil needs to be slipped back into its notch. A worst-case operation "in the field" would involve manually manipulating the ring with the diaphragm still on. This is the worst idea imaginable because it replaces the coil while wrinkling and possibly damaging the diaphragm. A better solution is to carefully deglue the surround, allowing a portion of the diaphragm to be lifted to allow a tool to be inserted, underneath the diaphragm, almost as if you were performing endoscopy. An even better solution is to unglue the entire surround so the entire diaphragm can be carefully lifted, allowing the coil to be reset/reinserted without putting undue stress on the diaphragm. Practically speaking, the very best solutions are to either replace the diaphragm or replace the driver(s).
The smart play would be to simply replace both drivers with a matching replacement pair. If you're going to handle this with the least amount of time and the least possibility of having to go back and fix the fix, tossing the old drivers and replacing them with matching drivers is the best approach. I suspect that's what Grado would do for $100, but only time will tell. I'll say this much: I've never read a thread that had anything bad to say about Grado service. People may grumble about the glue jobs or the occasional gimbal from Hell (mine fell off the right shell of my 325i, so I stuck it back on with instant glue). What you won't hear is a lot of noise about how Grado took somebody's money and gave them the finger.
(UK)
