I'll let you know what how mine turns out. The effects on ferromagnetic fluids are particularly intriguing, when one considers the effect of frequency on water. The fact that simply placing a magnet in the center and hooking it to an ipod gives you a speaker has some pretty mind blowing implications. I look forward to having a coil of my own, and seeing what I can do with it. Understanding the math is not required to build one, just a little curiosity.
This is the article that got my posting privileges revoked: