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Live compression + feedback
Old 14th July 2019
  #1
Here for the gear
 

Live compression + feedback

Ok so first post here. I’ve creeped for a long time and learned lots.

Over the last couple of years I’ve gotten into studio recording for my church which writes all its own music and began learning the concepts and principles to sound engineering and production and applying them to studio work. (EQ, Compression, gating, reverb/delay etc...)

I’ve also taken to slowly implementing those concepts into our live sets on the weekends teaching our sound volunteers these concepts a little at a time. We upgraded the sound system as well and we’re headed in the right direction I believe.

Earlier this year we installed an Allen and Heath SQ7 which is just awesome and has a ton of functionality.

But today I ran into an issue that I didn’t see coming and not sure what to do to troubleshoot it. I began explaining to our sound volunteers how compression can help make a lead vocal stand out more and glue things together however on our lead which was the only thing that had compression on it began to feed back with the onboard compressor engaged - 4:1 just at about 3db of compression and about 3-4db of gain make up. As soon as I’d disengage the compressor on the board feedback would stop. They also had some light reverb going as well.

Any ideas what would cause that? My understanding is feedback is a mic getting its own signal “looping” through it. How does a compressor cause feed back like that?

If you need more info please let me know.
Thanks in advance
Old 14th July 2019
  #2
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too much gain - do not use makeup gain if not really needed.

you didn't mention the preamp gain setting and mic type/model but with almost any widely used model, if gain is above +24dB, something is wrong. if vocals need to get compressed/gain compensated in order to get them through, you don't have enough rig for the gig or the singer has a very bad mic technique - you're in serious troubles if both is the case...
Old 15th July 2019
  #3
Here for the gear
 

Thanks for the reply - if memory serves correctly the input gain on the channel was at about +8dB. The mics are wireless Sure PG58’s.

I’ve always been under the impression that if you’re compressing say 2-3dB you always want to make up for that on the make up gain - is this not the case? Or is that a sometimes yes and sometimes no situation based on what you’re hearing? This is also using the onboard compressor of the SQ7. If that makes any difference.

Think I should also mention we do use stage wedges still as well.
Old 15th July 2019
  #4
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Quote:
Originally Posted by Snoochie View Post
Thanks for the reply - if memory serves correctly the input gain on the channel was at about +8dB. The mics are wireless Sure PG58’s.

I’ve always been under the impression that if you’re compressing say 2-3dB you always want to make up for that on the make up gain - is this not the case? Or is that a sometimes yes and sometimes no situation based on what you’re hearing? This is also using the onboard compressor of the SQ7. If that makes any difference.

Think I should also mention we do use stage wedges still as well.

assuming that the wireless system outputs line level (which is mostly around 20dB above mic level), +8dB would be too much... - compare with a hardwired sm58: if you still need but 8db of gain from the preamp, then the gain structure of the system is flawed (or the system severly overpowered for this location, which i doubt!)

a compressor's make up gain unfortunately adds - well - more gain (meaning level on the fader) which is not what you're after: you're after loudness if i got your description correctly.

a compressor is not the right tool to get something louder: you make things softer actually! you make a signal stick out less so it glues to the rest of the mix - to get something loud/make it stick out, you need a limiter.

i assume the compressor is post eq? (you might want to put it post fader).

nothing wrong with wedges! but how do they sound/measure? set the eq correctly, then put the mic up and get the gain structure right (until the onset of feedback, then back it down a bit); don't mess it up with a make up gain, use your ears and maybe an analyser to help you.

Last edited by deedeeyeah; 15th July 2019 at 01:57 AM.. Reason: edited
Old 15th July 2019
  #5
Here for the gear
 

Thank you for your help. I’ll be looking into this throughout the week. I’m sure I’ll be back to ask more questions.
Old 15th July 2019
  #6
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Quote:
Originally Posted by Snoochie View Post
..I’ve always been under the impression that if you’re compressing say 2-3dB you always want to make up for that on the make up gain - is this not the case? ..
No not necessarily at all. Consider that reduction on some of the peaks typically has little effect generally on a track's loudness.

FWIW I seldom use the make up gain, and often in 'presets it seems to be placed in there more to hype a plug's effect.
Live it can be a sticky situation -especially if in the monitors.
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