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Old 20th Jul 2022, 9:56 am   #21
Welsh Anorak
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Default Re: Could a speaker cause a fire?

To answer the question in post #12, it's a totally original and normal mid-range midi system with the STK in the main unit and a passive speaker connected by the thin wire I mentioned.
Like several of the above posts, I've had burnt out speakers and high-powered crossovers that have come to grief, but never doing any real damage. It's not a class D which I have had cause speaker damage, just a very typical system of the era which I would estimate has a power of around 20WPC.
We're waiting for the customer to come back with (hopefully) the remains of the speaker.
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Old 20th Jul 2022, 7:08 pm   #22
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Default Re: Could a speaker cause a fire?

Thanks Glyn, I find it hard to know why the speaker should “ be burnt to a crisp” #1, but if others have experienced this so be it. I’ll be interested to know what you discover, if you get your hands on the speaker.
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Old 20th Jul 2022, 9:07 pm   #23
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Default Re: Could a speaker cause a fire?

I had a loudspeaker under my bench at work connected to an amplifier on soak test. The amplifier developed a fault that put 40 volts supply rail across the speaker. I hadn't noticed until the flickering light from the flames caught my eye. I had to quickly scoop up and throw said loudspeaker into the yard outside much to the amusement of my work colleagues
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Old 20th Jul 2022, 9:22 pm   #24
Graham G3ZVT
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Default Re: Could a speaker cause a fire?

Did this happen this week?

I don't think the temperature quite reached the infamous "Fahrenheit 451“ though.
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Old 20th Jul 2022, 9:33 pm   #25
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Default Re: Could a speaker cause a fire?

Maybe an point to note.
The fire service saying a "speaker" caused a fire could mean any part of an audio system.
Quite often officials use generic terms to describe something.
Or they may be referring to the place where ignition probably occurred. Saying the ignition occurred at the speaker , does not mean the speaker itself caused the ignition.. It could well have been a cigarette end or other source.
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Old 21st Jul 2022, 9:36 am   #26
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Default Re: Could a speaker cause a fire?

Although we didn't visit the house, I'm under the impression the speaker was in an adjacent room.
Thinking about it, the amplifier was definitely faulty - IC and fusible resitor. It would seem quite a coincidence if this fault and the fire happened at the same time if the source of ignition was other than the speaker.
No sign of the speaker yet - I'll let you know with pictures if and when it turns up.
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Old 21st Jul 2022, 6:39 pm   #27
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Default Re: Could a speaker cause a fire?

I've also seen a speaker cone burned.
It didn't cause a fire as such due most likely to lack of oxygen and a metallic grille, it was a bookshelf speaker and not wooden. I'd suspect under the correct conditions it could be far worse, rare but quite possible.
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Old 23rd Jul 2022, 10:24 am   #28
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Default Re: Could a speaker cause a fire?

I've seen a few loudspeakers that have been on fire but only high power professional ones with a great PA amplifier driving them. In each case the speaker failed (I guess short) , causing the crossover components to heat up and ignite the polyester wadding inside. Some of these big pro amps can give out 200 volts or more (at least one amp manufacturer has the output of an amp driving a boiling kettle, for exhibitions).

https://www.youtube.com/watch?v=TM1cNG9Hxbo&t=2s
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Old 23rd Jul 2022, 12:40 pm   #29
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Default Re: Could a speaker cause a fire?

Another one here. I told them not to use that Fidelity UA3 amp.
https://www.youtube.com/watch?v=jT1DExsSLWQ
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Old 25th Jul 2022, 5:17 am   #30
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Default Re: Could a speaker cause a fire?

I spend the last years of my TV Engineer days working for a company that investigated suspected insurance fraud, relating to Brown and White goods for lost adjusters,
And I don't recall a ever seeing speaker, being the point of ignition, under normal fault conditions.
But I can agree with Glyn's theory of the STK device going short and putting 30+ volts across the speaker coil.
However, if the fire was caused by an external source, it would be blindingly obvious once the speaker was seen.
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Old 26th Jul 2022, 10:22 am   #31
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Default Re: Could a speaker cause a fire?

Are we going to see the offending speaker?
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Old 26th Jul 2022, 10:46 am   #32
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Default Re: Could a speaker cause a fire?

With sound systems of the past using typical outputs between 20-30w RMS I gave seen burnt out speakers, crossover units and scorched damping material. Generally not caused by a faulty amplifier just the amp running at near full volume for extended periods by teenage sons or daughters whilst there parents are away on holiday.
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Old 26th Jul 2022, 11:13 am   #33
Welsh Anorak
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Default Re: Could a speaker cause a fire?

Sorry Richard - I hope we do get to see it. We've been promised it by the customer but so far no show.
You'll be the first to see it, I promise!
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Old 29th Jul 2022, 1:19 am   #34
knobtwiddler
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Default Re: Could a speaker cause a fire?

Douglas Self seems to think that a speaker could catch fire: http://www.signaltransfer.freeuk.com/protect.htm
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Old 5th Aug 2022, 2:07 pm   #35
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Default Re: Could a speaker cause a fire?

Hi
Here's the offending speaker. Looking at the undamaged one, the driver has a thin foam cover, say 1mm thick, for some reason. It appears the front of the speaker went up, then dripped onto the carpet setting fire to it. The fire then spread up the wall and the side of a wooden cabinet. By this time the householder was aware and the fire was put out.
Makes you worry, though!
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Old 5th Aug 2022, 2:32 pm   #36
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Default Re: Could a speaker cause a fire?

Hmm, bit of a mess! Very hard to tell if it did start in the speaker, but it certainly looks like it did. I’m surprised there is any voice coil left though!

It is a bit worrying, I remember a certain Denon micro system that my Nan had which seemed to leave the amp running when in standby, you could hear it hissing! It was used in a bedroom too, so left unattended for a good number of hours a day, if that one had gone like this Technics one then her whole house would probably go up!

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Old 5th Aug 2022, 2:47 pm   #37
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Default Re: Could a speaker cause a fire?

Do you know what driver unit the voice coil came from?
The frame of the bass driver looks like it has been very hot with no plastic residue on it.
That voice coil looks like it was driven out of the magnet so that only half of it has been very hot while the other part was shielded by the magnet.
It would be interesting to see the other voice coil.
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Old 5th Aug 2022, 3:21 pm   #38
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Default Re: Could a speaker cause a fire?

So the flames may have started in the speaker, but the speaker wouldn't have been the root cause. That would have been a fault developing in the amplifier.

THe fault in the amplifier might just be a local happening, but with unregulated power supplies, a mains surge or transient could have initiated things.

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Old 5th Aug 2022, 5:01 pm   #39
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Default Re: Could a speaker cause a fire?

Glyn, thanks for the pics, from my experience in the past investigating Brown and White goods insurance fraud, I would be of the opinion that the damage was, "consistent with the insured's version of events".
But obviously the cause was originally, most likely a fault in the Amplifier.
Ken G6HZG.
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Old 5th Aug 2022, 5:33 pm   #40
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Default Re: Could a speaker cause a fire?

Yes, the amplifier was definitely at fault. The STK was severely dry jointed, and the .22R fusible resistor had blown. Likely it either put the HT rail across the speaker or went into oscillation as suggested earlier.
We have the other speaker so we can compare. Although not obvious from the picture, the voice coil is on a metal former.
The insurance company have no concerns about the claim.
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