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PA Problem

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PA Problem

Postby BigElectricCat » Sat May 07, 2011 4:33 am

Hi,

I just got a call from a friend of mine in another band. While they were setting up using a bar's PA they decided to try and plug some monitor speakers into the house board (some kind of large non powered output behringer).

When the guy plugged in an XLR cable to the monitor output the bass to the mains disappeared. They were unable to get the bass frequencies back. Unplugging the cable from the monitor output made no difference.

When he plugged the XLR cable in to the monitor out the system was running playing house music. The other end of the XLR was a jack lying on the floor.

Any ideas what happened?
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Re: PA Problem

Postby BigElectricCat » Sat May 07, 2011 9:25 am

I should have included more information.

After the mixer there is a crossover and power amps. There are 2 speakers on each side, one sub and one top.

That's all I know.

Any thoughts or suggestions are most welcome.
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Re: PA Problem

Postby TSH-Tim » Sat May 07, 2011 9:52 am

?? ??

There are 1000's of things which could of happened but it sounds to me like they have just unplugged the signal going to the subs.....

How I don't know but if there still having problems i would go back, unplug everything and start again.

Good luck
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Re: PA Problem

Postby BigElectricCat » Sat May 07, 2011 11:18 am

TSH-Tim wrote:?? ??

There are 1000's of things which could of happened but it sounds to me like they have just unplugged the signal going to the subs.....

How I don't know but if there still having problems i would go back, unplug everything and start again.

Good luck

Thanks for the reply. He told me he didn't touch anything else. He only plugged a cable into the monitor out. At that instant the bass disappeared and nothing he could do would bring it back.

He's concerned he 'blew a fuse'.

(as you can all tell none of us are PA guys)
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Re: PA Problem

Postby turbodave » Sat May 07, 2011 11:29 am

Hi, I would just make sure it is the monitor out and not a mono out. ...although without knowing the desk its difficult.Dave
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Re: PA Problem

Postby Mike Stranks » Sat May 07, 2011 2:44 pm

'Tis a puzzle...

The only Behringer large desks with XLR outs for the monitors are the LX series. In fact all the other B'ger large desks ONLY have XLRs on the main outs.

So unless we know the model of desk I think this will be a headscratcher....

My instincts (which are quite often not right!) are that he plugged into something that was different to what he thought it was - along the lines of what T'Dave has suggested.
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Re: PA Problem

Postby grab » Mon May 09, 2011 10:37 am

It's quite possible that although he didn't deliberately touch anything else, maybe he did catch a cable somewhere and didn't realise it.

For old jack sockets that are a bit worn out (and possibly weren't great in the first place; remember it's Behringer), it's very easy to pull out a jack cable. Maybe not far enough that it falls on the floor, but certainly far enough that it doesn't connect any more. And you might not notice that this one jack plug is 2-3mm further out than the one next to it.

Jack plugs are a really, really bad design on almost every technical level. For anyone looking at connectors, a jack plug is a classic example of what you should never do. Unfortunately they were a "just about good enough" design at the time, and when it became cheap enough to do a better job, there was too much user base to fight against.
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