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what do you do when the mains are blown?

Discussion in 'Sound, Music, and Intercom' started by Les, Mar 22, 2005.

  1. Les

    Les Well-Known Member

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    I work at a semi-professional theatre. That being said, what do you do when a 'semi-professional' volunteer blows your mains?
    We are doing the show Into The Woods and during tech week one of the sound guys was testing an effects processor to make a giant's voice. The voice they were using was very distorted and there is no compressor on the system. We heard them testing it while we were in the lobby and ran in there and told them to turn it down because we could hear the speakers distorting. The reply was "we have it set so it won't peak". Well the next day we came in and we couldn't get the main cluster to work. Only the left and right side speakers and monitors. Today we had a professional sound engineer come in who we have worked with before and he got them to work but it sounded terrible. He said that the diaphrams in the horns were blown. I know that in the cluster (which is concealed) There are 2 big independent horns and a main cabinet. Which do you think we should troubleshoot first? He said he thought they were probably no larger than 1" and would probably cost around $30. each.
    We were going to call the contracting company that installed the system back in '95 but he said they would probably over-charge. If we can get to them he said he would fix them for free with the right parts. The diaphrams he suggested were by JBL. Where do you think we should go from here?

    By the way, if my terminology is incorrect, it's because I'm a lighting designer. :)
     
  2. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    I assume that you cluster is flown? If so, how difficult will it be to have the cluster lowered so that it can be inspected? If you have to replace a diaphragm, you are going to have to access the horn.

    Obviously, the two horns would be the first place that I would look but what is loaded into the cab that you also refer to? If it is just drivers, then the horns are going to be the problem. If there is a horn in the cab, then it could be that one as well.

    I am surprised that once this guy isolated the source of the problem that he didn't go that one step further to narrow it down to a specific component. Then again, I do not know your theatre or how your gear is set up and therefore how accessible.

    Don’t be fooled by the visible size of the horns. Think of them as a trumpet (or horn) and think of the size of the end compared to the mouthpiece. In other words, the diaphragm is most likely to be 1” or 2” in diameter.

    If he were willing to fix them for what it costs in parts, then I would ask if (for a small fee) this sound guy will look at the cluster for you once it is on the ground and tell you exactly what you need.
     
  3. avkid

    avkid Not a New User Fight Leukemia

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    For $60, let him have a go at it. If that fix doesn't work, at least the cluster will be in the position to troubleshoot!
     
  4. Les

    Les Well-Known Member

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    I'm not sure how easy it would be to get the cluster to the ground. It is dead hung and concealed by a metal frame covered by fabric. If we take out the center seats in the second row, we may be able to get to the front. This theatre doesn't have alot of down time, so the less amount of time we spend on this project, the better. From the apron of the stage we can get to the back of the cluster on the lift. From what I did see, there is a loaded cab, but I'm not sure if there is a horn in there. Also, beside the cab there are two horns about 2' long and I guess about 20" wide at the front of the bell. Those should be easy to get to. I'm not sure if lowering the cluster will be an option. We would need to have the pro's come in and do it and I doubt they could get it done as soon as we need it. Hopefully the only horns are the ones that are easy to get to.
     
  5. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Well if the horns are easy(ish) to get to I would start there. But whilst you are there just see if you can take a better look at the cab. However, givine that you have two horns in the cluster I would assume that the cab is loaded with drivers only.
     
  6. wolf825

    wolf825 Senior Team Emeritus Premium Member

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    Hmmmm.....

    I would have this "Semiprofessional volunteer" pick up the bill for your repairs and be made responsible for getting them fixed immediately, or you will file a police report to have him arrested and charged for vandalism, and have the theater SUE him in civil court for damages & repairs, legal fee's and down-time costs of lost revenue the theater suffers, because of his blatent ignorance, negligence and abuse of equipment that is not his own..

    Thats what I would do...


    That said--sounds like you are stuck with either getting to the horns yourself or hiring someone to do it. From your description of the horns and where they are, they are probably JBL, Altec or Community...either way once you get to them (probably by scaffold or genie-lift with a raised balancer scaffold that goes over seating areas) that is not the hard part--opening them up IS usually the hard part. Most of those long and wide horns are well sealed and use recessed ALLEN screws and sealent in the magnet around the diaphram--in other words its not work you can do easily in the air.

    Also keep in mind--If you un-do the rigging to get them down--you are then voiding any warrenty and liability from the original company, and opening yourself up to a liability issues should they fall or have issues later on. Replacing a diaphram in a horn is simple...but getting to them and opeining them up in the air is not. I would suggest you get the original contractor who put the system in to do the repair...or at the very least supply you with the equipment list and drawings of the installation--it may shed some clues on how to proceed and the exact gear or parts you will need to get replaced...plus the theater may have a contract or service warrenty that may still be in effect with this company you may not know about.

    Doing the work yourself or with a friend--well that may be risky in liabilities, costs, damages and insurance coverages--should someone fall or be hurt while doing this repair work..or later on if the rigging you un-do should fail....

    just a few thoughts.. Good luck...
    -w
     
  7. Les

    Les Well-Known Member

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    The horns looked fairly lightweight. I believe they were mostly fiberglass and hung by brackets. So maybe just the horns alone wouldn't be too hard to get out. I wouldn't want to touch the cab, but as Mayhem pointed out, it is probably loaded with drivers only. I'll see if I can get to it sometime tomorrow and determine the caliber of rigging/take-down we will have to do. If it is too heavy, we will have it professionally done. As for the guy who did the damage, I just found out that he was a paid musical director for the current show. So he didn't even belong in the booth, but it was the first day of Tech and the staff was worried that the real sound guy wouldn't show up. I'm not sure if the MD has been told yet, but I'll run it by the Exec's and see what they have to say.
     
  8. Mayhem

    Mayhem Senior Team Emeritus Premium Member

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    Wolf raises some very good points and it was remiss of me not to warn you about heading up a ladder with a c-wrench. My thoughts were more along the line of ascertaining the accessibility of the horns to see what is possible to do without lowering them.

    The legal ramifications for the MD would be worth pursuing, especially if this turns out to be more that a $60 job. As you may be voiding a warranty in following this course of action, the cost savings don’t appear to be worth it.
     

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