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Crackling speakers

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josephwdowling
(@josephwdowling)
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Joined: 14 years ago
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We just finished playing a gig last night. It rained three [3] inches the day before , and I'm not too sure of the power we had--whether it was very conditioned or not, since we were outdoors on a platform in the middle of the street. The patform was wet, but my board and amp were elevated on a rack. The whole setup was of course surge protected and never has given me much trouble in the past.

Everything was setup right, we had a sound check and began to play. Right away, we had crackling from the mains when we pushed the high notes. I checked the amp, it was redlining a little. It is a Behringer 1500 watt. All my Electronic tech. buddies[I'm computer PC] tell me to turn the amp up all the way and work the mains from the board. That way, you get the best underlayment of power, right? Last night, no matter what I did , nothng helped. We still got crackles from the speakers -- just three vocal mikes were plugged in to the Behringer Eurolive board and the Behringer 1500 wat amp. I have the quick disconnect blue-ended speaker cables and I run instrument cables from the amp to the board. Are the mikes at fault? Nothing helped when I disconnected them and plugged back in. Nothing was getting hot or sounded shorting. I have taken the grills off the main speakers and they are not blown. I will try new speakers from a friend. Was it the humidity or bad power? I'm at a loss as how to prepare for that. Any help would be much appreciated.


   
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kent_eh
(@kent_eh)
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Joined: 17 years ago
Posts: 1882
 

Could be bad power.
Could be a damaged speaker. If the voice coil is damaged a visual inspection won't tell you much. That could happen from rough handling of the speaker cabinet (someone drop it?) or being overdriven at some point.
Does it affect only 1 speaker cabinet or all?

Does the crackle happen with specific frequencies, or above a certain loudness?
Can you try it out with a tape or CD and re-create the problem? If so it's clearly not related to the mics.

Can you re-create the problem between gigs?
Less pressure, and you can troubleshoot in a logical, methodical sort of way (change 1 thing, does the problem change? Restore that change, change something else, repeat test...)
All my Electronic tech. buddies[I'm computer PC] tell me to turn the amp up all the way and work the mains from the board.
Yup, that's the way I've always done it, and that's the way the big guys do it.

I wrapped a newspaper ’round my head
So I looked like I was deep


   
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leear
(@leear)
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Joined: 18 years ago
Posts: 392
 

kent has it right. however it sounds like they are clipping especially since you said your amps where hitting the red. now i own the same amps and i've learned the amp has it's limit even thoug they are great little guys. another thing alot of people here disagree about turning the amps all the way up, i however firmly believe in it I do it night after night big shows little shows, national acts, and it is phenomenal. the only time we don't is when we run the Crest amps we own. The CA12 has to be turned down because it will kill the CA9 powering the tops and all you will get is a lot of bottom from subs because we can't push anymore to the tops. (these are tri-amped systems).

I would do as kent said try it with a CD/Tape if it happens again then you just got closer to finding it. try a different speaker cable. try turing the amp down. then see if it happens.

What is probably occuring is your amp is clipping sending the clip to the speakers. Behringer speakers are bad about that(i'm assuming their behringer because everything else is) However my Yamaha amps can clip and you'll never hear it through the speaker (it's still bad though and I hate it) How is your EQ set. Make sure it's flat sometimes when you think it needs a little more highs or bass that little bit of an increase can cause that.

Boost EQ= Boost in volume/gain structure.

No matter where you go.... There You are! Law of Location


   
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Wes Inman
(@wes-inman)
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Joined: 19 years ago
Posts: 5582
 

I would disagree completely with turning your power amp up to max, and that is probably why you got all the cracks and pops. It is no different from turning your guitar amp to max, it will also make lots of noise. Of course, with guitar you might want distortion and even feedback and noises. This is never the case with a PA system.

The secret is to get the strongest signal from the beginning of the chain to the end. So first you want to make sure all mics are giving the strongest signal possible without clipping or distortion. That is the very reason you have clip lights on your mixer board, so you can do this very thing. Then you go step by step whether you run the signal next into an EQ, Compressor/Limiter, whatever. Now you will have the strongest, but clean signal going to the amp. Now, it is true that you want to leave a little headroom on your mixer so you can up the volume as the night goes on. But you will find if you use this method you will get FAR more power and volume out of your amps without all the noise. And many professional soundpeople say this is the proper method.

Here is a video showing the proper way to set gain structure, the exact opposite of what your friends told you.

http://www.expertvillage.com/video/27323_pasystem-basic-gain-structure.htm

I have owned and run my own PA for years. While I am no expert, I can get plenty of volume from my amps to fill the largest rooms without noise. Rarely are my amps even cranked to half power. Think about it, why would they put a volume control (really an attenuator) on your amp if it is supposed to be operated at max power at all times?? :roll:

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis


   
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Ricochet
(@ricochet)
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Think about it, why would they put a volume control (really an attenuator) on your amp if it is supposed to be operated at max power at all times?? :roll:
What I've been saying for years about guitar amps, too. :mrgreen:

"A cheerful heart is good medicine."


   
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kent_eh
(@kent_eh)
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Joined: 17 years ago
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Think about it, why would they put a volume control (really an attenuator) on your amp if it is supposed to be operated at max power at all times?? :roll:
A couple that come to mind are: permanent installs; situations where you want to balance different speakers/zones; when you have an amp that is overpowered for the speakers and you want to limit the output; when you don't trust the operator to exercise discretion.

I'm not suggesting that your approach is wrong, but I have experienced many large touring systems where the amps are left with no attenuation, and the level is entirely controlled from the crossover and board.
Different strokes, etc.

I wrapped a newspaper ’round my head
So I looked like I was deep


   
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Wes Inman
(@wes-inman)
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Joined: 19 years ago
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Well, nothing to argue about.

But here is a case where the amps were maxed and made noise all night. Nuff said.

If you know something better than Rock and Roll, I'd like to hear it - Jerry Lee Lewis


   
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leear
(@leear)
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Joined: 18 years ago
Posts: 392
 

its' one of those trial and error cases. My system is a Yamaha Club V (4) 18" and (2) 12"/horns PER SIDE. My amps match the speakers. Speaker can handle 400W RMS Max amp will push [email protected] So i turn them all the way up and control via DBX Drive rack, and board. I also limit my main mix. I push every last bit out of those amps before clipping sometimes.

But however as was stated installs and such are different. Even when I work for our big company we use a Dynacord XA2 system (1 of 5) Those amps the subs will kill the tops so we have to turn the sub amps down to about 3/4 power.

Like wes said nothing to argue about.

No matter where you go.... There You are! Law of Location


   
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kent_eh
(@kent_eh)
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Joined: 17 years ago
Posts: 1882
 

Well, nothing to argue about.
Nope, nothing at all.

There are many ways to set up a system, and a good number of them give perfectly workable results.

I wrapped a newspaper ’round my head
So I looked like I was deep


   
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