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Old 5th Aug 2022, 10:34 pm   #41
Refugee
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Default Re: Could a speaker cause a fire?

There is no doubt that the amplifier provided the heat that started the fire.
What we can't see is the voice coil that the fire started in.
The voice coil in the photo looks like it was lifted out of the magnet after the fire started as the part that remained in the magnet looks undamaged.
It would be nice to see a photo of the other voice coil as I would expect to see it burned all the way from end to end.
The voice coil in the photo looks like it was driven by a DC fault after the fire started so that only the part exposed to the heat got burned. It must have been driven out of the magnet by a DC fault that occurred after the fire started.
To me it looks like the other voice coil was the source of ignition.
It would be nice to know what driver the coil in the photo came from.
The LF driver looks like it has been very hot but it is not clear if the HF driver melted its way out of the plastic baffle board and fell swinging on its wires to set fire to the lower area.
The DC fault would most likely have occurred as the driver that got hot first failed due to shorted turns in the voice coil.
The only thing I am pretty sure of is that the fire did not start in the driver the coil in the photo came from. That coil was only exposed to the heat after a DC fault occurred in the amplifier with the heat of the fire already hot enough to visibly burn the coil. The burning on the coil is pretty even for half the length of the former and the remainder is pretty well undamaged. It would have been burned along its full length if it was where the fire started.
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Old 6th Aug 2022, 9:30 am   #42
Welsh Anorak
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Default Re: Could a speaker cause a fire?

I tend to agree. The HF coil can just be seen having dropped onto the basket of the woofer in the picture. I'll see if Andrew can take another photo as the speaker's in the shop.
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Old 6th Aug 2022, 10:37 am   #43
Radio Wrangler
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Default Re: Could a speaker cause a fire?

A DC fault would just heat the woofer and the tweeter coil would be protected by the series C in the crossover.

Oscillation could heat either or both, but the tweeter is more fragile.

The tweeter coil likely came out with heat from the fire, the wire doesn't look to have been that hot, So it looks like DC from the amp.

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Old 6th Aug 2022, 6:27 pm   #44
m0cemdave
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Default Re: Could a speaker cause a fire?

Yes, that is a classic example of voice coil burn-up due to the amplifier output going DC.
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Old 6th Aug 2022, 6:59 pm   #45
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Default Re: Could a speaker cause a fire?

Thanks Glyn for pictures, certainly made me think.
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