🚀 go-pugleaf

In article <18051@oasys.dt.navy.mil> geversti@oasys.dt.navy.mil (Gordon Everstine) writes:
>I have heard it said that the small speakers used in PCs can be used
>underwater.  Such speakers are very inexpensive.

this is probably the least expensive way to do this, but you won't get
hi-fidelity across a wide band of frequency.

a way that has been ably demonstrated to me by a friend is to put the
speaker element in a container filled with non-electrical conducting
(and non-flammable) oil, and then seal the container.  the oil fill
provides a good acoustical path and also provides equal hydro pressure
to the container and contents.  the good part is that a trip to a
supermarket for the oil and a tupperware container, and a trip to radio
shack for the piezo speaker element, is a small cost.   the bad part is
the speaker can't be driven hard (loud), and the directivity isn't that good.
if you are clever, you might be able to solve the directivity problem.

another way to do this is to alter a woofer speaker (8" or larger diamter)
by cutting away the cone, stamped frame and the surround.  leave only the
voice coil, spider, and magnet assembly.  Somehow how want to connect, via
cement, the voice coil to the inside face of a thin metal disk (a cookie
tin for example).  the speaker guts fit inside the cookie tin, and run the
wires out thru the back.  You will have to water seal the works.    basically
you are trying to alter a loudspeaker for air acoustics into one suited (but
by no means optimized) for underwater use.    moving coil underwater sound
sources have been around for many years and they do work.  if you are handy
with mechanical stuff and waterproofing, and are somewhat handy with electrical
components (speakers e.g.) you can make an underwater loudspeaker yourself.

ken rolt    grad student  /  mit ocean engineering
kdrolt@athena.mit.edu