Sound Buzz and static

[mikeep1331]

I need some help with our live sound pa setup. I dont have a lot of knowledge so some help would be appreciated. Our system consists of a pair of Behringer B2112D and 1 Behringer pro 1800d. We run a behringer zenyx 2222usb mixer with a dbx drive rack px. So finally to the question, when I turn on the speakers we get a decent buzz that will increase and decrease with the level adjustment on the speakers. Then when we turn on mixer and drive rack the buzz goes away but is replaced with a static noise. I have ran the wizard setup on dbx as well as auto eq and AFS. Also setup the gain structure to get proper limiting on all devises. If i turn the elves down on the speakers it leaves almost no headroom at the mixer for channels or main outputs. Any thoughts on this would be great. Thanks

[tacitus]

So what's the noise level like compared to how loud the speakers are with your normal signal going through them? In other worse, is this "background noise" we're talking about, or severe "malfunction type noise"? There's going to be something, especially if you run powered speakers at full volume (not saying you shouldn't, but turning them down a notch at the speaker usually quietens them a bit, which may be good or bad depending on how loud the noise is and how loud you want to go altogether).

I suspect there may be little bit more background noise on Behringer kit than some others, but it shouldn't be loud enough to get in the way. Buzz changing to hiss may be down to what's connected and what's turned up at any given moment. I suggest you plug the mixer directly into the speakers and set all possible EQ controls in the path to flat to see what you have before you start messing about with anything. If the noise is anything more than barely audible, there's a proper problem somewhere and you need to eliminate all the factors such as poor earthing, poor cables, dodgy contacts and so on that are, overall, more likely than equipment failure. One thing that might catch you out is using 1/4" jack speaker leads to connect your active speakers to the mixer - if they're proper speaker leads they won't be shielded and assuming you have the option, XLR leads will be more reliable. Shielded jack leads will be fine, too.

Also, in my admittedly limited experience with Behringer kit, it doesn't usually like running at extremes, so try arranging all your gain/volume settings so they are in the 80-90% range rather than full on.

Anything more I say now would be wild guesswork, as opposed to intelligent guesswork, so maybe you can let us know about your connections, typical pot settings and mains power configuration.

[tacitus]

Just had a look at the B212D speaker brochure and it looks as if the input level is set on a single pot ranging from mic input when it's turned all the way up through line input and on to nothing at all when it's turned all the way down. In this situation having it turned right up will be the wrong thing to do - try it around half-way up, or better still, set the mixer outputs to the loudest signal from there and gradually turn up the speaker gain knob until it's the right volume. Too much gain on the speaker knob will mean having to turn the mixer down too low and the combination of those will give you more noise than the other way round.

You need to fit the sub in here somewhere, but I need a moment to look at the specs for that. Usually it's mixer to sub to speaker.

[mikeep1331]

Well all my connections are xlr. My levels on the speakers are relatively low, a little lower than 12 oclock on the knob. The noise is back round noise but gets quite a bit louder when I adjust the knob to say 1-2 o'clock. The problem is when I have the levels down and the noise quiets down it leaves me no headroom on the mixer. My gain is up to 3/4 value on my mic, with the channel fader and the main faders almost all the way up. Someone said that the buzz that I have when there is no signal is probably a ground loop. Any suggestions or thought on this being the issue? I do appreciate the help. Thanks