[sdiy] About infrasounds

[Dave Krooshof]

>The main problem
>is to amplify them, right?. Then, you only have to reduce the
>vibrating membrane frequency of your amplifier.
>If the equation of a vibrating membrane is
>
>f = Sqr (S/M) / 2 * D
>
>Where S = stress, M = mass and D = diameter.
>
>As reducing stress is difficult and increasing the diameter almost
>impossible... Should increasing the mass of the membrane a valid
>solution?. It's easy (soaking it with jelly or something like that)
Agreed.

Under my seat is a body shaker. It's a speaker, sort of, but
not a Moving Coil, but a Moving Magnet. A 1Kgram iron
magnet is hold  by two spirals of viberglass. It's held
in the middle of a round metal box, in which the coil is
glued. The magnet is moved when AC is fed through the coil.
They are CHEAP.
It's a stupid design though. A screw sticks out, so I had
to drill a hole in order to free the movement. And they
managed to have a resonance in it.
It gives the feeling the music is realy loud!
It didn't cause any injuries yet. :-)


Ddddaverr


Come to think of it. The viberglass suspension is probably
to increase the stress. Also the strength of the magnet
add up to this. The membrane is big: it's about the size
of my chair.


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