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Author Topic: Smoked some drivers, time for a lesson.  (Read 4789 times)

Steve Crump

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Smoked some drivers, time for a lesson.
« on: September 18, 2018, 11:48:26 AM »

I had a scenario happen at our venue Saturday night that has happened to me before at a different venue and need some advice.

Previous event: I was setting up sound at a golf course ballroom, just had received a new QU-16, I sent vocals to the effects and returned on the effects and blew out two HF drivers. The amp I was using had clip limiters, and the speakers had integral protection, but the loop still destroyed the HF drivers. This scenario is not the one I need advice on specifically, because this is history and I know what caused my problem. I only posted this part of the story to make the point that with protection I still lost drivers.

Saturday night: From what I can understand from talking to the sound guy who handled the show Saturday night, is that he did a similar scenario with the effects when he was finishing up sound check and blew out the LF drivers in both the hanging FOH speakers.
We dropped the boxes yesterday, (EV QRX115) and both cabinets have smoked drivers. Now here is the part I hate to admit. The amp I am driving these cabinets with has no speaker protection. I am using the digital console for processing and cheap'd out and didn't buy a management system. Our venue is a cracker box and the system is not pushed that hard. My question is, if I would have had a amplifier with built in protection could it have saved the drivers? I mean it didn't at the ballroom...

As far as the sound guy, he is experienced and competent, he just made a mistake.

Need some schooling here....
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Ken Braziel

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Re: Smoked some drivers, time for a lesson.
« Reply #1 on: September 18, 2018, 11:52:01 AM »

What style of music?

Asking because certain types of electronica have a lot of square waves, which can wreck your drivers at levels way below the rated peak. You need massive headroom to run stuff like dubstep.
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Steve Crump

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Re: Smoked some drivers, time for a lesson.
« Reply #2 on: September 18, 2018, 11:59:24 AM »

What style of music?

Asking because certain types of electronica have a lot of square waves, which can wreck your drivers at levels way below the rated peak. You need massive headroom to run stuff like dubstep.


It's live bands only, Blues mostly.
But I can tell you from my experience that the loop created by the effects being sent back to the effects is very continuous.
What I am trying to figure out is while I am changing out the drivers, should I put an amplifier with  integral protection or would it have really helped in this scenario.
« Last Edit: September 18, 2018, 12:02:33 PM by Steve Crump »
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Chris Hindle

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Re: Smoked some drivers, time for a lesson.
« Reply #3 on: September 18, 2018, 12:33:58 PM »


It's live bands only, Blues mostly.
But I can tell you from my experience that the loop created by the effects being sent back to the effects is very continuous.
What I am trying to figure out is while I am changing out the drivers, should I put an amplifier with  integral protection or would it have really helped in this scenario.
A runaway feedback loop will go until the "chain" is broken.
Usually that is a blown speaker if you're not fast enough on the console.
A limiter, carefully set, may help, but it is no guarantee.
Set it too tight, and you lose too much headroom, too loose and you could still lose drivers.
Chris.
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Mark Wilkinson

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Re: Smoked some drivers, time for a lesson.
« Reply #4 on: September 18, 2018, 01:09:18 PM »


My question is, if I would have had a amplifier with built in protection could it have saved the drivers? I mean it didn't at the ballroom...


What specific amp? 
It didn't have a clip limiter?

I can only speak about a bunch of different QSC amps that have all measured similarly....but the clip limiter on them acts like a compressor, preserving waveform more than not...IOW it doesn't turn sine waves into square waves.
So the clip limiter basically limits RMS voltage to a "particular voltage".
And with the clip limiter in play it just comes down to whether the driver can take that "particular voltage" for however long the driver was juiced.
By 'in play', I mean clip lights on rather steadily..
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Mike Monte

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Re: Smoked some drivers, time for a lesson.
« Reply #5 on: September 18, 2018, 01:14:50 PM »

I had a scenario happen at our venue Saturday night that has happened to me before at a different venue and need some advice.

Previous event: I was setting up sound at a golf course ballroom, just had received a new QU-16, I sent vocals to the effects and returned on the effects and blew out two HF drivers. The amp I was using had clip limiters, and the speakers had integral protection, but the loop still destroyed the HF drivers. This scenario is not the one I need advice on specifically, because this is history and I know what caused my problem. I only posted this part of the story to make the point that with protection I still lost drivers.

Saturday night: From what I can understand from talking to the sound guy who handled the show Saturday night, is that he did a similar scenario with the effects when he was finishing up sound check and blew out the LF drivers in both the hanging FOH speakers.
We dropped the boxes yesterday, (EV QRX115) and both cabinets have smoked drivers. Now here is the part I hate to admit. The amp I am driving these cabinets with has no speaker protection. I am using the digital console for processing and cheap'd out and didn't buy a management system. Our venue is a cracker box and the system is not pushed that hard. My question is, if I would have had a amplifier with built in protection could it have saved the drivers? I mean it didn't at the ballroom...

As far as the sound guy, he is experienced and competent, he just made a mistake.

Need some schooling here....

I had a bit of "learning curve" going from my Mixwizard to my QU-16. 
My specific issue was with the Mix outs (monitor sends).  You definitely do not want to clip them...

Overall the QU-16's outputs seem "hotter" than the Mizwiz.

   
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Paul G. OBrien

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Re: Smoked some drivers, time for a lesson.
« Reply #6 on: September 18, 2018, 01:19:11 PM »

An amp with adjustable voltage limiters.. not just clip limiters could have prevented blown drivers if set correctly.
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Tim McCulloch

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Re: Smoked some drivers, time for a lesson.
« Reply #7 on: September 18, 2018, 01:29:10 PM »

Smoking drivers - probably bad for your health... ;)

This is where the RMS/"long term" power limiters come into play.  With the equipment currently at hand, the quick answer is that nothing would have prevented the voice coil destruction.

Long term power handling isn't what manufacturers claim in the "single number" specifications, and the success of power limiting is dependent on program material and how much system output you're willing to sacrifice for driver longevity (see Chris H's post).
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"If you're passing on your way, from Palm Springs to L.A., Give a wave to good ol' Dave, Say hello to progress and goodbye to the Moonlight Motor Inn." - Steve Spurgin, Moonlight Motor Inn

Steve Crump

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Re: Smoked some drivers, time for a lesson.
« Reply #8 on: September 18, 2018, 01:30:11 PM »

What specific amp? 
It didn't have a clip limiter?

I can only speak about a bunch of different QSC amps that have all measured similarly....but the clip limiter on them acts like a compressor, preserving waveform more than not...IOW it doesn't turn sine waves into square waves.
So the clip limiter basically limits RMS voltage to a "particular voltage".
And with the clip limiter in play it just comes down to whether the driver can take that "particular voltage" for however long the driver was juiced.
By 'in play', I mean clip lights on rather steadily..

QSC PLX at the ballroom, previous time

Crown XLi at the venue. This time.
« Last Edit: September 18, 2018, 01:32:33 PM by Steve Crump »
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Mark Wilkinson

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Re: Smoked some drivers, time for a lesson.
« Reply #9 on: September 18, 2018, 01:38:59 PM »

QSC PLX at the ballroom, previous time

Crown XLi at the venue. This time.

Hi Steve, ...the Crown, what specific model? 
If it was small enough the clip limiter might have saved them...
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Re: Smoked some drivers, time for a lesson.
« Reply #9 on: September 18, 2018, 01:38:59 PM »


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