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[Todd Leighty]

Here is the situation. High school stadium, simple sound system: Rolls rack mixer, two Shure ULX receivers( antennas mounted outside the press box) plus one wired mic, and a cd player all in metal rack. output to  behringer ultradrive 2496  then to two QSC amps to 4 community R1's on the light poles over the stands.
The press box is manned by different people depending on which sport or organization is using the field. The problem is we keep blowing drivers in the R1's. limters are set on the processor and amplifier, no visible clipping on processor or amplifiers meters even when driving system to high level.
  However I think I have narrowed down the problem to a spike in signal and a noise over the system when a walkie is keyed in the press box. I know the easy solution is no walkie in the press box but due to the amount of different people using the press box I was hoping for a suggestions that may protect us against people that don't follow the rules.
Thanks in advance as always
 

[Don Boomer]

You likely have several problems that need correcting, but your limiters need adjusting if you are blowing drivers. You didn’t say whether you are blowing high or low drivers but I’m gonna guess your attack time needs to be lessened. Setting limiters is always a trade off between protection and sound quality unfortunately.

After you solve that you can work on how the walkie talkies are getting into your system.

[Erik Jerde]

You likely have several problems that need correcting, but your limiters need adjusting if you are blowing drivers. You didn’t say whether you are blowing high or low drivers but I’m gonna guess your attack time needs to be lessened. Setting limiters is always a trade off between protection and sound quality unfortunately.

After you solve that you can work on how the walkie talkies are getting into your system.

Good advice unless the OP is correct about the walkies and the signal intrusion is happening after the limiter.

[Brian Jojade]

Step 1 is figure out why the walkie talkies are getting into the system. If it's creating enough noise to damage the speaker, then it's got to be annoying as heck for the audience.

Step 2. Limiters don't always protect speakers.  In fact, set incorrectly, a limiter could make things worse as it could square off the signal wave and result in a higher average power than you are expecting.

[John Roberts {JR}]

Here is the situation. High school stadium, simple sound system: Rolls rack mixer, two Shure ULX receivers( antennas mounted outside the press box) plus one wired mic, and a cd player all in metal rack. output to  behringer ultradrive 2496  then to two QSC amps to 4 community R1's on the light poles over the stands.
The press box is manned by different people depending on which sport or organization is using the field. The problem is we keep blowing drivers in the R1's. limters are set on the processor and amplifier, no visible clipping on processor or amplifiers meters even when driving system to high level.
  However I think I have narrowed down the problem to a spike in signal and a noise over the system when a walkie is keyed in the press box. I know the easy solution is no walkie in the press box but due to the amount of different people using the press box I was hoping for a suggestions that may protect us against people that don't follow the rules.
Thanks in advance as always

decoding RF into audio interference is called rectification and often a consequence of RF getting into circuit paths that aren't fast enough, or filtered enough to ignore it.

If it is happening in the press box, look at the gear in the press box. Something there is not rejecting /ignoring the RF. This could be almost any active circuit... I have even seen RF sneak back into amplifiers vis speaker wires.

Your press box... give it a close inspection.

JR 

[David Sturzenbecher]

In fact, set incorrectly, a limiter could make things worse as it could square off the signal wave and result in a higher average power than you are expecting.

Please explain

[Kurt J Nemer]

FWIW, I have experienced a DCX2496 picking up RFI on the input. Adding an external 1:1 isolation transformer on the input fixed it. Sometimes the bandwidth limitations of a transformer is a good thing.

[Steve M Smith]

decoding RF into audio interference is called rectification and often a consequence of RF getting into circuit paths that aren't fast enough, or filtered enough to ignore it.

Dirty contacts can rectify RF too.  A bit like the cat's whisker detector as found in early crystal receivers.


Steve.

[Mike Caldwell]

Are you using balanced audio connections everywhere?

[Caleb Dueck]

Are you using balanced audio connections everywhere?

Any way you can swap out the Rolls for testing? 

If the CD player has RCA unbalanced outputs - can you test a different source (say PC and Radial USB-Pro)?

[Todd Leighty]

 The fans definitely heard  the walkie keying through the system. I have balanced connections from the mics and from the mixer to the amp, RCA inputs on cd player and aux in. I have swapped out the Rolls with another mixer with the same results. I will try removing the cd player from the system to see if that helps.
Thank you to everyone that has offered suggestions.
-Todd

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