speakers start on fire at Local Hockey Rink

Adam Whetham

Adam Whetham

Sophomore
Jan 11, 2011
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Grand Forks, ND
Link: http://www.grandforksherald.com/event/article/id/208650/

Quote from article

A fire broke out Sunday in Ralph Engelstad Arena in Grand Forks, causing significant damage to electronic equipment and arena ice. Smoke damage also occurred throughout the building.

“From a venue perspective, we’re assessing the damage and attempting to determine the cause of the fire. Nobody was hurt, and the fire was exhausted quickly,” said Chris Semrau, director of events and marketing at the arena.

Grand Forks Fire Department Capt. Bruce Weymier said damage to the sound system and building is estimated to total $1 million to 1.5 million.

"This was a significant fire," he said.

The fire was located in the catwalk area of the building, making putting it out a tricky task.

"We had to go up stairwell and go through the press box to get to the catwalk,” said Weymier. “We had to stretch a lot of hose.””

About 600 feet of hose was used to reach the fire and 150 gallons of water was used to extinguish it.

Bruce Weymier said the department was dispatched to the call shortly before 1 p.m. Sunday afternoon.

An employee entered the arena’s loading dock area about 12:50 p.m., smelled burning plastic and called 911.

Weymier said a set of drop-down speakers was the origin of the fire. UND Police and Altru also responded to the call.

The cause of the fire will be investigated by electricians, the Grand Forks Fire Department and the N.D. State Fire Marshal.
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I'm friends with a few of the technical guys there, and the right now they're going through security footage of the arena. Seems there was a basketball sized explosion out the back of the speakers, and then it started smoldering and burning. Then half of the hang crashed to the Ice.

Speakers are JBL PD series from what I remember. Macro-techs powering them. Rigging buddy said the burned cabinets they pulled from the ice had pretty intact speakers still, didn't appear to be the voice coils that burned. Amps are pretty much always on in this venue, not sure why a relay system isn't' in place.

Here's a picture of the inside of the arena. I've circled one of the hangs to give an idea. the whole thing didn't come crashing down, by the sounds of it 2-3 cabinets of it did.

Not sure if the PD series has a crossover in the back of the speaker? that caught fire somehow and caused a fire?
 

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Re: speakers start on fire at Local Hockey Rink

Ben Lawrence said:
Yikes! 1-1.5$ million in damage.. I guess it could have been a lot worse.
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A lot of that is smoke damage. When they designed the building they didn't think anything up in the metal rafters could start on fire. so no sensors were installed. so it was actually phoned in before the system tripped. all the merch inside is smoke damaged, along with the damage the speakers did to the ice surface/boards/plexi.
 
Re: speakers start on fire at Local Hockey Rink

I have actually had a couple of speakers catch on fire.

One was from a burnt voice coil that caught the paper on fire.

One was from firworks after the concert and a "wayward" rocket landed on top of my carpet covered speakers (with flamable glue).

The most spectacular was at a Mexican wedding. Dummy here-decided to cheap out (the band did not pay for lights-but then wanted them anyway-so I just threw up a rack of 4 par 56's w/500 watt bulbs in them and just plugged them into a 20A circuit and put them on top of the PA. no dimmer paks-no stands.

A little while later there was all this "activity" around the stack that was away from me. People where shaking up soda bottles and spraying them on the cabinets to try and put out the fire. The bulbs had gooten so hot they started the carpet to burn. OOPS!

I've had LOTS put out a good bit of smoke when they "blew". Never had one explode however. But I have had them fall on top of a car-when it ran under the scaffolding and the scaffolding collapsed and dumed the PA on the car and the ground.
 
Re: speakers start on fire at Local Hockey Rink

JBL's torture test room in Northridge had a hand truck by a quick exit door so they could wheel a burning box outside right away. Of course they were testing models before they went out and into use in order to suss out issues like this. This case sounds like an amplifier failure. Like a DC300 gone awry.
 
Re: speakers start on fire at Local Hockey Rink

drew gandy said:
JBL's torture test room in Northridge had a hand truck by a quick exit door so they could wheel a burning box outside right away. Of course they were testing models before they went out and into use in order to suss out issues like this. This case sounds like an amplifier failure. Like a DC300 gone awry.
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While amps are often quick to be blamed-I would argue that most of the time this is not the case.

Let's take the case of the typical amplifier that goes "DC" and does not have any protection against this DC getting to the output/speaker.

The loudspeaker on the other end (in most cases) would die a VERY quick death. This would produce very little heating of anything except the voice coil. The driver would open up before anything else could get hot.

And if the crossover would start to be suspected of the cause of the burn-let's look at that. On the high freq side the first thing in line is a capacitor. That would stop the DC from going any further-(capacitors act an open to DC) so no damage there.

On the woofer side of things-the "basic" crossover is a coil in series and possibly a cap in parallel with the woofer. So the coil will pass the DC just fine (as if it were a piece of wire-which it is at DC) and onto the woofer voice coil. The voice coil would open-and then the current flow would simply stop. There is nowhere for the voltage on the other side of the coil to go-remember that the parallel cap will block the DC.

So while the loudspeaker will "die" from an amp "going DC"-it is not likely to cause it to catch on fire.

It is real easy to "jump to conclusion", but often we have to look a bit further into what the REAL causes may be.

I HIGHLY doubt it is was an amp that "went DC". An amp that was oscillating-however- would be a different story.

Another note about the Crown DC300's. I hear them "blamed" at lot for "going DC". I think this is mostly in the name. THe name is there because the amp does not have any capacitors in the signal path-so that it can have a response all the way to DC. In fact they have often been used as a DC power supply-I have done it myself to power a console.

In all my years as a bench tech-both for music stores and my own repair businesses-I have NEVER had a DC300 come in for repair that had "gone DC". I'm not saying they can't, but I never saw it in all of my years. It was usually a distortion at higher power levels (once it got past the class A stage) that was the cause.

I do have an "official" Crown service manual for the DC 300. The name is "300 watts and a puff of smoke".

All I am saying is there are MANY MANY things/ideas in this industry that get "thrown around" without any first hand experience or any basis. Somebody says it-and it gets passed on and on and on etc.
 
Re: speakers start on fire at Local Hockey Rink

Oh yeah. Sorry for stirring the pot with red herring. (btw, oscillation was my thought too but I had to throw another Harman brand product into this particular thread on purpose;)
 
Re: speakers start on fire at Local Hockey Rink

drew gandy said:
Oh yeah. Sorry for stirring the pot with red herring. (btw, oscillation was my thought too but I had to throw another Harman brand product into this particular thread on purpose;)
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Yes while Crown is a NOW a Harmon brand-back in the DC300 days it was not.

For those "in the know", the current Crown is not the same "type" of comapany that it was back then.
 
Re: speakers start on fire at Local Hockey Rink

Ivan Beaver said:
Yes while Crown is a NOW a Harmon brand-back in the DC300 days it was not.

For those "in the know", the current Crown is not the same "type" of comapany that it was back then.
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Founded by missionaries? Nope, that isn't the Sidney Harman way... Dr. Harman was a brilliant guy in a lot of ways, but to my knowledge he never founded a company because of his religion.
 
Re: speakers start on fire at Local Hockey Rink

Gene Hardage said:
Without reading the whole thing too carefully it sounds like the lawyers will be going after the deepest pockets first although it seems that the general contractor may be more to blame for this one.
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This is my opinion regarding legal information (not legal advice!!!!)

Generally all parties are named in the suit resulting from injury or property damage and may then be held jointly and severally liable. The plaintiff can recover 100% of the award from any one defendant who then must sue the other parties for their portion. This is still the common law rule. Tort reform in most states (including ND) mean that they are only liable for their portion of the fault except for in specified circumstances that vary state to state.

I suspect, however, that this suit is based on product liability and therefore is only applicable to the manufacturer. The news clip alleges negligence but it's not clear whether that's on the basis of (negligently) failing to warn of some foreseeable risk or (negligently) allowing a defective product out of their warehouse (or some other cause of action....)

I draw this distinction because it raises the multiple bases for which one may be held liable. Liability as a manufacturer is something different from liability as a contractor. The insurance companies see it this way as well, generally requiring separate policies. Take this as a note of caution for those who make things and then put them in public places. Your insurance may not be covering you!
 
Re: speakers start on fire at Local Hockey Rink

Wouldn't that be speakers end on fire?

While I suspect some share of DC300s failed DC (common result of shorted power transistor), but most amps use FUSES (now circuit breakers) so not typically fire starters (a focus of UL safety testing). However, if the DC comes in through an input, the DC amplifier will not be stressed and put out the amplified DC until something downstream fails. A DC300 pegged full positive or negative output will not be internally dissipating any significant power in it's output devices so keep on trucking, as long as the current draw doesn't take out the fuses.

IIRC there are safety agency rules dealing with flammability of speaker cabinets used in proximity of internal power amps that may have very hot parts during faults.

I'll forgo the way too easy second guessing in hindsight.

JR
 
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