[MarkB]

Hello all, newbie, so please forgive me if I'm covering a subject
which is old or obsolete...

I heard some time back of some speakers being made to create
ridiculously low-freq noise by effectively swapping the electro-
magnetic part of a large bass speaker for something that was servo
driven. Myths abound, but I'd heard that various armies may have used
this to recreate "real" bomb noises on firing ranges to test the
mettle of those in training...

Anyone know of a project, or even better some plans along these lines
so I might experiment with my own ULF speaker(s)...

Of course, if there's a better alternative then I'd be interested to
hear that too...

Cheers all, Mark.