Intermittent low frequency buzz

Chaos is Born

Active Member
This buzzing problem just came up today during our matinee show of How to Succeed in Business. At one point there appeared a fairly loud low frequency buzz from one of our speakers. I have checked all personal wireless mics and all other inputs to the board and nothing. I have checked our outputs and still nothing. This is the first time it has happened all season and we have been running this show for almost a week and haven’t had any problems with this up till earlier today.

If you need information on what amps and speakers we are using I can provide that later when I can get the exact numbers from them.

Any suggestions would be greatly appreciated.
Was this something that just happened for few seconds / minutes ? Please let us know how long it lasted. Also, was it a single frequency or single set of frequencies, or did it change frequencies? Abit more detail on your setup would also be handy.
First thing that popped into my head is lighting equipment (read: dimmers) on the same circuit, but, now that I think about it, doesn't make sense, if this just popped up today, still could have something on the same circuit that doesn't belong there.

Do you have a system processor b/w your console and amps? I've heard of instances where there is a processor that can provide test tones for testing the system, maybe a low frequency tone could have found it's way into your mix.

BTW, what part of the show did the LF buzz show up? We did the show last year.
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Ah, H2$. What a wonderful show. I'm curious as to how you do the game show scene - we built a giant TV and ran a live video feed to it...

Anyway, the first thing I would check the run from the console to the speaker and the equipment in between. Pay careful attention to connections and cables, as well as equipment power cords. If someone tripped on one and broke a solder connection or a pin, that may be the cause. Failing that, try swapping the bad signal path with a good signal path at different points, and see when the buzzing moves from one to the other.
Chaos How many weekday matinees have you done of this show? Why I ask is to find out whether the noise was induced by someone during their workday. Ie are people near your venue using two-way radios etc. Are there cleaners or office workers in other parts of your building who aren't normaly there during night / weekend performances. If so if they run things like vacums, photocopiers etc and they are the same main suppl as you this might cause the interfernce.

One of the ways to check this is to see if the interfernce occurs tonight. If it doesn't then is probably what I suggest.

If you still get the interfence tonight then probably someone has done something different. For instance is it hot in the dressing rooms or the pit and has someone decided to use a fan to cool themselves. Has someone moved some leads backstage from where you put them. You get the idea.

If the inteference is still there I would swap over the leads to the loudpseakers, remembering to swap the input leads, if the buzz moves speakers then it is coming from the output of the desk.

You said you tried the different leads after the show was the interfernce still there?

Have you tried playing music through just that speaker in case it is starting to fail?

Hope this helps please let us know how you get on. As this will give us all more suggestions that we can use the next time we have the same problem.
Ok, well the show went off tonight without a hitch. No problems whatso ever with a buzz or anything of the sort. I wish i could give more details as to what the buzz sounded like. However it was our artistic director that noticed it when he was standing near it durring the show.

The TV scene was just done on stage live nothing fancy or anything really, just a giant treasure chest.

As of now, i doubt it was any two way radios. I am in a town of about 54 people in the middle of nowhere.

Once i can replicate the problem i can give more details. But since it has only come up once and i was told about it and didn't hear it myself... I can't give much more information at this time.
You have to love those problems that fix themselves! Let us know if it comes up again. Sometimes the hardest problems to fix are the ones that arnt consistant, because they never seem to act up when you are testing and trying to figure out what is going on, but they always show up on the night of the big show!
Loose ground wire in-line with a LF/sub driver?

That could explain the intermittentcy of the hum. If it didn't get jostled then it wouldn't be a problem, but the minute somebody touches and amp/processor/etc.. with the bad wire it'll start to go.
Well I figured it out. Turns out of my XLR feeds to the amps soldering came loose and was crossing with the ground on the EQ for both amps. Just a little bit of resoldering and the problem has been solved.

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