It may work as a strong motion sensor. I agree with Ted, usually you want the natural period of the sensor to be longer than the lowest period you want to record.
Speakers usually have few turns.
What you describe maybe the begining of a force balance sensor but you would need a displacement sensor included which would complicate matters. You could then put a rectangular magnet on both sides of the coil. As Ted says you probable will have more interesting events if you do not attach the groung to the end of the boom except as I have described above. I hope this helps a little. I don't think this will work.