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Bad mics and Blown Speakers

Discussion in 'Safety' started by mbandgeek, Apr 18, 2006.

  1. mbandgeek

    mbandgeek Active Member

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    During a talent show last year for my school, one of my friends was running sound, and when a dancer got up on the stage all four of the EV floor monitors were blown By the music started playing (ironically the song was "Toxic" by Brittney spears). It was toxic for our sound system that day. I was laughing for about 5 minutes after he blew four monitors.

    Also in the same show. Three of the microphones on stage started to not work. then we had four blown monitors, and three broken Microphones. The funniest day of my life.
     
  2. nez

    nez Member

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    all i have to say is it sounds like an expensive day lol
     
  3. mbandgeek

    mbandgeek Active Member

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    It was we had to find replacements We found 2 monitors that we didn't even know the school had, along with 2 Powered 2 way speakers, so we lost 4 found 4. Didn't find any mics though.
     
  4. soundman1024

    soundman1024 Active Member

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    How loud was it????
    Most mics don't blow unless it is ridiculously loud. Loud beyond reason. I'm not sure if 4 monitors blowing would be enough, it depends on the monitors. Is it jus the low frequency driver blown or the whole cabinet? If its just the LF driver it might be cheapest to get the speakers repaired.

    Suggestion: limiters in line before the amplifiers can prevent this from happening.
     
  5. tenor_singer

    tenor_singer Active Member

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    Makes me wonder how large the dancer was to make that level of noise as they moved around the stage. :S
     
  6. Chris15

    Chris15 CBMod CB Mods Premium Member

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    It may not seem great, but I don't think its the end of the world. The blown speakers aren't that hard to fix. I'll summarise the way to do it. Should anyone require further details or clarification, please ask.
    1] You need to work out which driver or drivers inside the speaker have blown.
    2] You then need to take the grill off and pull the broken driver out and write down the brand, model, part number, etc. Do this for all the blown drivers.
    3] Once you have compiled this list, give your nice friendly dealer a ring and ask them to order you the voice coils for all those blown drivers. Alternatively, you may be able to source them directly from the manufacturer or some other place.
    4] Once your voice coils have arrived, you want to completely remove the blown drivers from the cabinets, disconnecting wiring as needed, but recording what went where so that your speaker still works properly at the end of this and the cabinets are not out of phase to each other.
    5] Take the driver and carefully remove the cover off the back.
    6] Carefully remove the old voice coil and insert the new one.
    7] Reattach the back and put the driver back into the cabinet.
    8] Test your repaired speaker, being sure to start at a low volume so that if something is wrong, you won't immediately blow your new coils.

    If you could send us a picture of the blown voice coil, I should be able to tell why it blew. There are two main causes and they show up differently on the blown coil. It could be prolonged overloading or it could be a spike, caused by something like a mic dropping or being plugged in with phantom on and the channel up.

    Now for the blown mics. If their Shure, replacement is the most viable option. A new capsule is close to the price of a new mic and so it is not worth your while trying to fix it. On the other hand, some brands are worth fixing, so you would want to be calling a dealer to find out what a new capsule is worth. It should then be as simple as unsoldering the old capsule and soldering in a new one. The thing being, that it might be worth your while to get a dealer to replace the capsule if you are a bit unsure. I know that my dealer charges about AU$30 to replace a capsule and the Sure capsules are like AU$20 cheaper than a new mic so you can see why I say that it is uneconomical.

    Dropping mics does have a tendency to destroy capsules so that may be why they blew.

    Well done on finding things you did not know existed, now if you can get the blown ones fixed, you have increased your inventory.
     
  7. soundman1024

    soundman1024 Active Member

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    Also lets not rule out the possiblity that it is a blown channel on the sound board.
     
  8. cutlunch

    cutlunch Active Member

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    If I had 4 speakers blown in one show I would be worried as to what caused them to blow. Especially at a school where you will have to justify the cost of getting them fixed.

    The things I would be doing is work out how they blew, and how to repair them.

    You said these were being used as monitors how were they wired? Were they wired to more then one channel or all wired in parallel. If the last case then the impedance was probably to low causing more current to flow then they could handle.

    I would also check the amplifier is OK and hasn't blown a fuse.

    I had a look at some of the service manuals for EV and some speaker models show fuses. If you go to EV you should find the service manual for your speakers. Hopefully you have only blown fuses.

    Please let us know what the problem is when you find it also could you post the model of the speakers as people may have had similar problems.
     
  9. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Thinking a little further, I will add to my recommendations. What I have posted above should fix blown drivers and busted mics, but what I neglected to include was that at this point, you would be well advised to do a full check of your system. If in fact you have blown the speaker drivers and the mics themselves, then the above steps should mean that they can be repaired. However, as soundman1024 noted, you would probably want to check your mixer channels. You would also want to check your amps, not only the fuses, give them a check as you may have done internal damage. That is where it could get messy.

    You might wan to consider what you were doing when all this happened. Mic damage was likely caused by impact from a drop and speaker damage by either continued overload or an excessively high peak.

    Maybe you could fill us in on what was happening when you sustained this damage. We then might be able to offer a better idea of what to do to stop it from happening again.
     
  10. soundlight

    soundlight Well-Known Member

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    And, as some have said, make sure to limit the signal with a good, fast-attack limiter.
     
  11. saxman0317

    saxman0317 Active Member

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    Also, i found that druing stuff like that when im running band shows around town, i like to put compresson in on, or even better use a board with it built in like a mackie digital in school.
     
  12. mbandgeek

    mbandgeek Active Member

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    It was really loud. The act that blew the mics was for a rock band that had all of their amps turned all the way up.

    That might have been the act that did the KO punch on our monitors as well.

    The whole speaker, well the cardboard type stuff was shreaded. like someone just tore it into a few pieces.
     
  13. audioslavematt

    audioslavematt Active Member

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    The SPL had to have been up over 130 on the stage. That is beyond the threshold of pain. How the "rock band" could even stand to be on the stage in that kind of noise is beyond me, unless they were deaf.
     
  14. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Here that are legal limits on the maximum levels of sound exposure. If the cone is shredded, you either need to recone or replace. Here it is 85dB for 8 hours is the limit with no peak greater than 140dB. For each 3dB increase, exposure time needs to be halved. Beyond these levels, hearing protection is required.

    I know bands that play with ear plugs in. I would be concerned for the safety of the band, the crew and the audience if the concert was as loud as it would appear from the damage.

    Industrial deafness results from extended exposure to sound at high volumes and it is not something that you want.
     
  15. mbandgeek

    mbandgeek Active Member

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    It was recently fixed, but i can explain what it looked like. All the Cardboard stuff was all torn. there was also some thin clear plastic underneath the cardboard that had a big tear in it. other than that it seemed to be okay. No capacitors were blown or anything.
     
  16. mbandgeek

    mbandgeek Active Member

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    There amps were faced toward the audience, and they stood behind them. the only thing they needed to hear was the voice of the singer, which came out of the monitors. But our auditorium doesn't have the best acoustics, but he had to have the monitors turned up all the way. it was a wonder that there was no outstanding feedback.
     
  17. Chris15

    Chris15 CBMod CB Mods Premium Member

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    The only time that one finds a capacitor in a speaker is when is is part of an Emergency Warning and Intercommunication System (EWIS) that is connect to your fire alarm. It is there so that the integrity of the wiring can be monitored with an end of line resistor and not affect the audio. So I would hope that you did not blow a capacitor. The amp blowing a capacitor is another story though...

    That was not a dead voice coil then, though the plastic beneath the cardboard, was it mounted so that it stuck out and was about 1/2" wide? If so, that is the voice coil. I unwisely assumed that we were talking about damage caused by audio peaks and loud volumes, not mechanical abuse as this would appear to be.
     
  18. Chris15

    Chris15 CBMod CB Mods Premium Member

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    Think about it, if a speaker cone is oscillating in time with the music, as it has to, it will push air in both directions, so you will get a reasonable amount of sound out the back of one of them.

    I would have to agree with audioslavematt on this one, that would have been uncomfortable.
     
  19. avkid

    avkid Not a New User Fight Leukemia

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    But not too fast either,as you don't want really abrupt frequent cuts all the time.
     
  20. TimmyP1955

    TimmyP1955 Active Member

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    The power to each speaker would not change, but the amp's clip point would be at a lower power level per speaker (as compared to having the speakers fed by more amp channels).

    My guess is that the monitors were asked to produce a lot more low frequency information than they were capable of. A high pass filter would be advisiable, 100Hz is a good place to start.
     

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