Just be sure the foam is OPEN CELL foam and not closed cell foam. Closed
cell makes good padding but won't hold water like a sponge. Open cell will
hold a good bit of water.
Fiberglass, the pink stuff, works also quite well and has been used for
years. Most speakers either have an open back, or if an enclosed cabinet
then a slot in the front known as a port or a slot with a tube attached
extending toward the back of the cabinet known as a tuned port. All of this
depends on the cabinet volume and the free air resonance of the speaker.
73
Bob, K4TAX
----- Original Message -----
From: "Rob Atkinson K5UJ" <k5uj@hotmail.com>
To: <tentec@contesting.com>
Cc: <k5uj@hotmail.com>; <kd7efq62@hotmail.com>
Sent: Friday, August 01, 2003 12:32 PM
Subject: [TenTec] Re: 2 minor comments: Speakers and Centurion
> Hi Todd;
>
> The foam is speaker enclosure baffling material. It's used to lengthen
the
> space the sound has to travel through without increasing the size of the
> cabinet. This is a method used in cabinet design and is often found in
> stereo speakers. Baffling flattens the frequency response of the unit and
> boosts the bass response slightly. If you have an old speaker in a
cabinet
> you can try buying some foam rubber at a hobby/crafts shop, cutting it to
> fit across the inside of the cabinet and put it in behind the speaker and
> hear the difference. Large bass speakers with cones that move a lot will
> need an air tube exiting from behind the speaker either through the
baffling
> or through the front to equalize the cabinet air pressure when the cone
> moves suddenly. I doubt if this kind of speaker is used in ham radio
> however.
>
> 73,
>
> Rob
> K5UJ
>
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