"Dave Plowman (News)" wrote in message
...

In article ,
David wrote:
It is intended to contain and stop a fire spreading in the void of a
suspended ceiling should the fire start in the speaker.

Crikey. I've seen a few fried speakers - but one which went on fire? ;-)

Its not the voice coil of the speaker that causes the problem, but on 100V
line systems it's usually the matching transformer that can go AWOL. And on
a large system, all that audio power can heat up the transformer fairly
quickly.