Hi,
following on from the "Relay contact rating" thread - here is a neat page on the use of small relays to protect loudspeakers from being destroyed by a faulty amplifier.
Many stereo amps have relays to eliminate annoying switch on and off noises and most of them disengage the speaker if a significant DC voltage is detected on the output of one or other amp channel.
However, very few such relays will ACTUALLY protect the speaker from the full DC rail voltage - eg if an output device fails etc. All that happens is a permanent DC arc develops across the open contacts, destroying the relay AND the speaker.
The page include pics and several nice videos of the author's experiments with this problem.
The idea of shorting the speaker terminals with a changeover relay is as suggested to Rod Elliot by myself and included in his ( ESP ) page on the topic - this new page takes up the gauntlet and runs with it.
To see the vids, you will need a " g3p" codec with your video viewer.
I guess the author took the vids with his mobile phone.
.... Phil