That's interesting and is actually relevant to my project. I'm using the magnets to vibrate strings (hence the 100-500Hz range) and ideally I want the strings to start vibrating as quickly as possible when pulsed, so I might have to look into spiking the voltage for the first few hundred milliseconds or so. I'm controlling the magnets with an ardunio and L293D H bridges that are fed a constant 12V from a fairly hefty power supply (so no noticeable voltage drop under load). Do you have any suggestions for how I would go about spiking the driving voltage for the initial pulses?
Oh, so not even 12V, but 10V...
L293 is pretty shit, it's old and best forgotten. A MOSFET bridge (with logic level inputs) is available almost as cheaply, while capable of more voltage and current, faster, and with less voltage drop. (I don't have a number handy.)
That said, the contemporary solution would be L297.
You might as well get an integrated coil driver -- yes, there are ready-made ICs for this!
So, that said, to "pluck" the string as fast as possible: consider this is a linear system, from coil voltage/current, to string wobbling. You're fine, it's fairly instantaneous even at a tiny voltage. As long as you don't mind having a small deflection. If this is an electric guitar, just turn up the gain. SNR may be worse, feedback may be worse, but there's probably enough dB inbetween to get away with it.
Now, if you know how much deflection you need, then you simply need that much coil drive times the mechanical gain of the magnet.
Note that mechanical gain depends wholly on how strong the field is. Is this an air cored bobbin, to be fit onto something? Does this have pole pieces? Surely you need to extend the pole pieces with a nose, so that they pluck just one string, not "most" of them? If there are no pole pieces, it's just about hopeless, the field from an air core coil is very weak indeed. You will gain far more from adding pole pieces, than going from a AA battery to anything that has been discussed here!
Tim