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Author Topic: Lets open up the fused/bulbed speaker can of worms shall we???  (Read 6099 times)

John Sabine

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 Ok.. Pulled down 4 Community R series speakers from a stadium this week and upon examination discovered that the horn driver and woofer are blown in every unit plus the light bulbs in the protection circuit are blown. I'm thinking about just bypassing the bulbs because obviously they didn't do their job and if I've got to go up 40' to pull a speaker I'd rather not have to wonder if its the bulb or the driver.
 What say ye M'asses?
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Andrew Broughton

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #1 on: August 25, 2014, 07:01:18 PM »

Sounds like it was hit with a huge spike (inspection of the horn diaphragm and woofer will tell you exactly what killed them) before the lamp could blow. The lamp takes a certain amount of time before it blows, so it will only protect from too much continuous power, not from anything instantaneous.

Nothing to be gained from removing it, but much to be gained from better protection upstream.
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Dennis Wiggins

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #2 on: August 25, 2014, 08:05:30 PM »

Ok.. Pulled down 4 Community R series speakers from a stadium this week and upon examination discovered that the horn driver and woofer are blown in every unit plus the light bulbs in the protection circuit are blown. I'm thinking about just bypassing the bulbs because obviously they didn't do their job and if I've got to go up 40' to pull a speaker I'd rather not have to wonder if its the bulb or the driver.
 What say ye M'asses?

This method of protecting drivers goes back to (at least) the early 60's.  It works by the fact that as the filament heats up, it has a higher resistance.  This reduces current to the driver being protected.  Of course, as was pointed out, the filament will take some time (at least a few milliseconds) to heat up.  I would not shunt them.

-Dennis
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Ivan Beaver

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #3 on: August 25, 2014, 08:17:56 PM »

Ok.. Pulled down 4 Community R series speakers from a stadium this week and upon examination discovered that the horn driver and woofer are blown in every unit plus the light bulbs in the protection circuit are blown. I'm thinking about just bypassing the bulbs because obviously they didn't do their job and if I've got to go up 40' to pull a speaker I'd rather not have to wonder if its the bulb or the driver.
 What say ye M'asses?
Since they are R series, I suppose they were outside.

That means that they could be exposed to lightning.  That can do all sorts of damage.

There are some gas surge suppressors out there that go across the speaker line and short when exposed to a voltage over their rating.

Were the bulbs in the woofer section or just the HF/mid section?  I know Community uses bulbs for HF protection in a number of products (or used to use)-I am not sure about now.
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Ivan Beaver
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John Sabine

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #4 on: August 25, 2014, 08:27:07 PM »

actually the damage was from a "dj who knows a lot about sound equipment " who decided the system sounded better with all protection turned off and a smiley face eq.
 I haven't traced the circuits to see if the bulbs are in both the high and low pass circuits or just the high. will do that later this week.


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Ivan Beaver

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #5 on: August 25, 2014, 08:47:15 PM »

actually the damage was from a "dj who knows a lot about sound equipment " who decided the system sounded better with all protection turned off and a smiley face eq.
 I haven't traced the circuits to see if the bulbs are in both the high and low pass circuits or just the high. will do that later this week.


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Well it sounds as if they have somebody who should pay for the repair---------------

The protection circuits are based around "kinda normal" operation-and to provide protection against things that get "out of normal".

You cannot protect against everything with a simple circuit-but it can add a measure of protection.

Overexcursion is something the bulbs can't do much about.  That is probably what killed the woofers.

Are the HF drivers OK?
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Ivan Beaver
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John Roberts {JR}

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #6 on: August 25, 2014, 08:51:45 PM »

Just because protection can't protect against everything is no reason to not use it at all. How many service calls did it save you?

JR
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Ivan Beaver

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #7 on: August 25, 2014, 08:58:56 PM »

Just because protection can't protect against everything is no reason to not use it at all. How many service calls did it save you?

JR
Yeah-I forgot to talk about that part.

I WOULD NOT bypass the bulbs.

There are many times that accidents happen so fast that even a knowledgeable sound person could not react fast enough.
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Brian Jojade

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #8 on: August 25, 2014, 10:59:05 PM »

The cool (and bad) thing about bulbs is that they act as a compressor on the HF driver.  As they light up, the bulb uses up some of the power that would be going to the driver, reducing the output.  This is better than just a fuse that blows when power hits a certain level.  You'd be replacing fuses for any little incident, which would be a pain.

The good about it is that it will protect against over powering the driver.  The bad is if the bulb isn't sized right, it will start to affect the sound before it should. Still, having them in place isn't the worst idea.
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Brian Jojade

Mike Monte

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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #9 on: August 25, 2014, 11:46:18 PM »

actually the damage was from a "dj who knows a lot about sound equipment " who decided the system sounded better with all protection turned off and a smiley face eq.
 I haven't traced the circuits to see if the bulbs are in both the high and low pass circuits or just the high. will do that later this week.


Sent from my iPhone using Tapatalk

""actually the damage was from a "dj who knows a lot about sound equipment ""

enough said....

I have provided sound for DJ's... besides doubling the subs/power....limitters x2 ARE your friend.
Mike M 
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Re: Lets open up the fused/bulbed speaker can of worms shall we???
« Reply #9 on: August 25, 2014, 11:46:18 PM »


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