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Feedback and compressors
Old 24th September 2021
  #1
Feedback and compressors

I am having all kinds of problems with compression on my vocal mic, and I need to find some kind of solution.

It is, well, pretty much the problem you would imagine. Too much compression leads to too much make up gain, and then the PA feedsback at the drop of a hat. The issue here is that it's a very screamy metal band, and I need compression both to get a consistent level and also to save my voice. And of course the mic is peaking and clipping too, far too regularly which sounds dreadful.

I do have some hardware compressors but obviously I am doing something wrong because settings that (to me) look mild just result in screaching. The mixers we have available in the practise rooms are cheaper Behringer ones. They do have a compressor in the effects section, but it's just one setting that says "compressor". No tweaking of anything else. Not very promising.

I can drop a compressor into the insert section, or run one before the desk in the signal chain, and I have a compressor that is part of a channel strip that has a pre-amp (although I suspect this has only made problems worse previously).

I have been messing about for three practise sessions with no luck whatsoever and I wanted to get some more professional opinions.

How would you wire this us to get some much needed compression (if only to avoid the clipping!) without feeding back?
Old 25th September 2021
  #2
Gear Guru
 
1 Review written
🎧 5 years
many factors (but ultimately wrong gain staging) can lead to feedback...

first of all, use a mic with reasonable sensitivity (most likely a dynamic mic if you're on a loud stage), appropriate pattern (cardioid or hypercardioid) and use the gain trim to get up to level: then position wedges accordingly (different setup required for cardiod than for supercardioid), tweak wedges (cut critical frequencies - or switch to in-ears which has its own set of issues though, albeit not related to feedback):

if you're not getting enough level, a comp won't be the right tool to use! you might gain another 3-6dB before feedback by using an expander (not a gate) but mostly likely, you will need to lower other sources/reduce noise from backline/wedges/sidefills.

there's no way around the fact that the loudest signal at the mic wins...

now, insert a comp post eq: apply compression as needed but don't throw off the level balance by applying too much make-up gain.

don't feed too many other instruments (if any!) into your wedge(s): dial in only what you absolutely need to hear which mostly like is you (and maybe a bit of rhythm guitar) but not a full mix - this goes for everyone else in the band too!

all of this usually takes about a minute or two; maybe you wanna get some help from an experienced live sound monitor tech?
Old 25th September 2021 | Show parent
  #3
Quote:
Originally Posted by deedeeyeah ➡️
many factors (but ultimately wrong gain staging) can lead to feedback...

first of all, use a mic with reasonable sensitivity (most likely a dynamic mic if you're on a loud stage), appropriate pattern (cardioid or hypercardioid) and use the gain trim to get up to level: then position wedges accordingly (different setup required for cardiod than for supercardioid), tweak wedges (cut critical frequencies - or switch to in-ears which has its own set of issues though, albeit not related to feedback):

if you're not getting enough level, a comp won't be the right tool to use! you might gain another 3-6dB before feedback by using an expander (not a gate) but mostly likely, you will need to lower other sources/reduce noise from backline/wedges/sidefills.

there's no way around the fact that the loudest signal at the mic wins...

now, insert a comp post eq: apply compression as needed but don't throw off the level balance by applying too much make-up gain.

don't feed too many other instruments (if any!) into your wedge(s): dial in only what you absolutely need to hear which mostly like is you (and maybe a bit of rhythm guitar) but not a full mix - this goes for everyone else in the band too!

all of this usually takes about a minute or two; maybe you wanna get some help from an experienced live sound monitor tech?
I get the basics of what is happening, but it's incredibly frustrating to hear almost word for word "the gain staging is wrong".

Sure, I get it, I am doing it wrong now. How, specifically, can I get some useful amount of compression and avoid feedback?

And yes, compression is the tool that's correct here. No, I'm not using a comp to make myself louder. I'm using a comp so that the loud parts don't clip, and so they are somewhat closer to the quieter bits.

The thing about screamed vocals is that if you try and project them loudly like you would clean, powerful singing then you wreck your voice. You use compression with more gain so that you come out loud when you're singing which much less force, and you never try to use your voice to "sing over" 100w stacks. You lean on the mic, that's what it's there for.

What I need is advice in how to set this up.

Is the only real answer here to have a scope and a parametric EQ and just manually attack the feedback frequencies?
Old 25th September 2021 | Show parent
  #4
Gear Guru
 
1 Review written
🎧 5 years
Quote:
Originally Posted by LostTheTone ➡️
I get the basics of what is happening, but it's incredibly frustrating to hear almost word for word "the gain staging is wrong".

Sure, I get it, I am doing it wrong now. How, specifically, can I get some useful amount of compression and avoid feedback?

And yes, compression is the tool that's correct here. No, I'm not using a comp to make myself louder. I'm using a comp so that the loud parts don't clip, and so they are somewhat closer to the quieter bits.

The thing about screamed vocals is that if you try and project them loudly like you would clean, powerful singing then you wreck your voice. You use compression with more gain so that you come out loud when you're singing which much less force, and you never try to use your voice to "sing over" 100w stacks. You lean on the mic, that's what it's there for.

What I need is advice in how to set this up.

Is the only real answer here to have a scope and a parametric EQ and just manually attack the feedback frequencies?
one can hardly convey enough context in a short post to cover all possible shortcomings of the approach and gear used in a specific context - and pls note that i did not say using a comp is crap, on the contrary! i didn't suggest to scream at the top of your lungs all the time either...

...but the point is that if you can't get enough level without using a comp, then the problem mostly likely is to be found elsewhere!

a comp does not always need to be the right tool, could well be that you'd be better off with a limiter! this depends on the comp and/or lim and their settings (and gain staging if using multiple devices) and there's a massive difference between (the perception of) average levels and peaks...

anyway, start by comparing a few different mics: not all anymals are equal... - split the signal so you can tweak signals (in terms of gain, eq and dynamic processing) for monitoring and foh individually. and of course you're notching out the offending frequencies with a peq (or way less precisely with a geq) on the aux sends!

for maximum level/gain before feedback, you can also mis-use your vocal mic as a measuring mic (and thentweak the monitors accordingly)...
Old 25th September 2021 | Show parent
  #5
Quote:
Originally Posted by deedeeyeah ➡️
one can hardly convey enough context in a short post to cover all possible shortcomings of the approach and gear used in a specific context - and pls note that i did not say using a comp is crap, on the contrary! i didn't suggest to scream at the top of your lungs all the time either...

...but the point is that if you can't get enough level without using a comp, then the problem mostly likely is to be found elsewhere!

a comp does not always need to be the right tool, could well be that you'd be better off with a limiter! this depends on the comp and/or lim and their settings (and gain staging if using multiple devices) and there's a massive difference between (the perception of) average levels and peaks...

anyway, start by comparing a few different mics: not all anymals are equal... - split the signal so you can tweak signals (in terms of gain, eq and dynamic processing) for monitoring and foh individually. and of course you're notching out the offending frequencies with a peq (or way less precisely with a geq) on the aux sends!

for maximum level/gain before feedback, you can also mis-use your vocal mic as a measuring mic (and thentweak the monitors accordingly)...
To be clear - I'm not saying I can't get volume without a compressor, I'm saying the opposite. I'm saying that when I set the gain correctly for one style of singing, another style is vastly too loud and distorts.

Yes, I know mics aren't equal. I have Shure SM58s, various Audix mics and an sE Electronics V7. All of them have the exact same problem and feedback at the same point. Yes, they are pointing away from the PA speakers.

That's why I say it's frustrating to hear "the gain staging is wrong" because that's right from the FoH handbook. Yes, obviously there is too much gain in the system. But how can we improve matters from here?

For example - Should all compression be running as an insert in the mixer? Rather than up front before the mixer? Is it better to have more gain before the comp, with a higher threshold, or after the comp on the master out?
Old 25th September 2021 | Show parent
  #6
Gear Guru
 
1 Review written
🎧 5 years
Quote:
Originally Posted by LostTheTone ➡️
To be clear - I'm not saying I can't get volume without a compressor, I'm saying the opposite. I'm saying that when I set the gain correctly for one style of singing, another style is vastly too loud and distorts.

Yes, I know mics aren't equal. I have Shure SM58s, various Audix mics and an sE Electronics V7. All of them have the exact same problem and feedback at the same point. Yes, they are pointing away from the PA speakers.

That's why I say it's frustrating to hear "the gain staging is wrong" because that's right from the FoH handbook. Yes, obviously there is too much gain in the system. But how can we improve matters from here?

For example - Should all compression be running as an insert in the mixer? Rather than up front before the mixer? Is it better to have more gain before the comp, with a higher threshold, or after the comp on the master out?
guess we're not on the same page...

- with any source, set gain for maximum input without clipping the preamp
- use (most any) dynamic processor as post-eq, pre-fader insert
- do not use any dynamic processor for gain staging: use it only to compensate the attenuation which depends on level, threshold and ratio.
- with a loud voice, ca. 24dB of gain from the preamp on most any mixer should do when using a sm58
- if used as a comp, start with ca. 10-20ms of attack, 50-100ms of release, threshold anywhere between -30 to -18dB, ratio ca. 6-10:1.
- use faster attack/release times, higher threshold and ratio when used as a limiter; only apply as much make-up gain as you attenuate!
- these mics do NOT all feed back with the same setting...

...and if you're getting feedback in the pa (!?)/not in the monitors, you're either doing something awfully wrong, your pa is simply not powerful enough or extremely badly set up/unsuitable for the task!

___


rather than musing about any possible issues on a theoretical level, let me repeat my previous suggestion which is to get help from an experienced live sound tech in your town to guide you through each step of setting up things correctly - good luck!

___



p.s. how do you hold your mic?

Last edited by deedeeyeah; 25th September 2021 at 04:49 PM.. Reason: p.s. added
Old 25th September 2021
  #7
Lives for gear
 
🎧 5 years
deedeeyeah is, as usual, right on all this.

The problems that you describe do appear to indicate that you're out of your depth on this one, and it's not easy to diagnose what you're doing wrong without being there with you. Quite likely, an experienced engineer would instantly observe what needed to be fixed, hence the suggestion that you employ someone capable to help you out.
Old 27th September 2021
  #8
Gear Addict
 
🎧 5 years
Quote:
Originally Posted by LostTheTone ➡️
I am having all kinds of problems with compression on my vocal mic, and I need to find some kind of solution.

It is, well, pretty much the problem you would imagine. Too much compression leads to too much make up gain, and then the PA feedsback at the drop of a hat. The issue here is that it's a very screamy metal band, and I need compression both to get a consistent level and also to save my voice. And of course the mic is peaking and clipping too, far too regularly which sounds dreadful.

I do have some hardware compressors but obviously I am doing something wrong because settings that (to me) look mild just result in screaching. The mixers we have available in the practise rooms are cheaper Behringer ones. They do have a compressor in the effects section, but it's just one setting that says "compressor". No tweaking of anything else. Not very promising.

I can drop a compressor into the insert section, or run one before the desk in the signal chain, and I have a compressor that is part of a channel strip that has a pre-amp (although I suspect this has only made problems worse previously).

I have been messing about for three practise sessions with no luck whatsoever and I wanted to get some more professional opinions.

How would you wire this us to get some much needed compression (if only to avoid the clipping!) without feeding back?
You don't supply much specific information but I imagine to avoid singing loudly you are using too much preamp gain, compressing the signal and gaining it up again which leads to feedback at the drop of a hat. You have to sing loud to compete with the stage volume. No gear can fix a singer who doesn't sing loud enough.
Old 28th September 2021
  #9
Lives for gear
 
🎧 5 years
Quote:
Originally Posted by LostTheTone ➡️
I am having all kinds of problems with compression on my vocal mic, and I need to find some kind of solution.

It is, well, pretty much the problem you would imagine. Too much compression leads to too much make up gain, and then the PA feedsback at the drop of a hat. The issue here is that it's a very screamy metal band, and I need compression both to get a consistent level and also to save my voice. And of course the mic is peaking and clipping too, far too regularly which sounds dreadful.

I do have some hardware compressors but obviously I am doing something wrong because settings that (to me) look mild just result in screaching. The mixers we have available in the practise rooms are cheaper Behringer ones. They do have a compressor in the effects section, but it's just one setting that says "compressor". No tweaking of anything else. Not very promising.

I can drop a compressor into the insert section, or run one before the desk in the signal chain, and I have a compressor that is part of a channel strip that has a pre-amp (although I suspect this has only made problems worse previously).

I have been messing about for three practise sessions with no luck whatsoever and I wanted to get some more professional opinions.

How would you wire this us to get some much needed compression (if only to avoid the clipping!) without feeding back?
I think you are using the wrong tool for the stated job.

Compressors don't just limit high output, they boost low output. If all you want to do is keep a crazy loud singer from clipping the channel, use a limiter instead of a compressor (one could argue that a limiter is a specialized compressor though).

Secondly, try lowering the gain on the microphone and raising the fader to give you a better range on your preamp. For a crazy loud singer that is guaranteed to snow you on sound check, put the gain on the sound check at about 1/4 of the way up the VU meter (I know, old term). When he screams, that should give you quite a range before clipping even without a limiter.

Compressors cause feedback. No getting around it. Don't use them unless you have a system with PLENTY of gain before feedback headroom or you will EITHER severely limit the PA output level you can get OR the system will squeal.

If you are using wedge monitors, you need to make sure they are setup in the "blind spot" of each mic. Monitors are almost ALWAYS what feedback first. If you are using crappy monitors, it is highly likely they are one of the biggest sources of feedback (compression still makes it worse).

Turn down all the instruments on stage and then lower the monitor levels. You would be surprised how far this will go to eliminating feedback.
Old 28th September 2021
  #10
Lives for gear
 
🎧 10 years
Rather than trying to use gear to repair the issue, avoid the issue to begin with. Learn how to hold the mic in the right position for each volume you sing. Mic technique is the answer.
Old 30th October 2021
  #11
Lives for gear
 
GreenNeedle's Avatar
 
🎧 5 years
Quote:
Originally Posted by LostTheTone ➡️
I am having all kinds of problems with compression on my vocal mic, and I need to find some kind of solution.

It is, well, pretty much the problem you would imagine. Too much compression leads to too much make up gain, and then the PA feedsback at the drop of a hat. The issue here is that it's a very screamy metal band, and I need compression both to get a consistent level and also to save my voice. And of course the mic is peaking and clipping too, far too regularly which sounds dreadful.

I do have some hardware compressors but obviously I am doing something wrong because settings that (to me) look mild just result in screaching. The mixers we have available in the practise rooms are cheaper Behringer ones. They do have a compressor in the effects section, but it's just one setting that says "compressor". No tweaking of anything else. Not very promising.

I can drop a compressor into the insert section, or run one before the desk in the signal chain, and I have a compressor that is part of a channel strip that has a pre-amp (although I suspect this has only made problems worse previously).

I have been messing about for three practise sessions with no luck whatsoever and I wanted to get some more professional opinions.

How would you wire this us to get some much needed compression (if only to avoid the clipping!) without feeding back?
A couple things come to mind…
-you need a more powerful PA to get over the room sound
-you need to set the threshold on the inserted compressor higher, so it only grabs peaks, don’t run it in compression all the time.
Old 31st October 2021 | Show parent
  #12
Lives for gear
 
🎧 15 years
Start with the 100w stacks...good metal tone is not about volume. Have the whole band turn TF down and give the front of house guy/girl some room to work
Old 2nd November 2021 | Show parent
  #13
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avare's Avatar
 
🎧 15 years
Quote:
Originally Posted by elegentdrum ➡️
Rather than trying to use gear to repair the issue, avoid the issue to begin with. Learn how to hold the mic in the right position for each volume you sing. Mic technique is the answer.
This is it. Just as an example, back off on the mic when singing loud.
Old 2nd November 2021
  #14
Lives for gear
 
🎧 5 years
Mic technique is definitely a thing here, but if you want a deep tone as you're belting out loud passages then you'll need to be closer than mic technique will allow you to control the volume, so compression is the answer there.

There's also the annoyingly frequent vocal style now where some passages of songs are quiet and breathy over a loud stage volume. If you want your monitors clear for that and also for belting vocals right on the mic then yeah you'll need compression and an excellent monitor tech. You can't trust house techs to pull that off. That's where IEM's are very called for.

Regardless, using a mic with especially good feedback rejection is key to how much compression you can achieve. Gotta go hypercardioid, my faves are the EV N/D737a, Audix OM5 (or higher), and if you're a Shure fan the Beta58 is pretty good. Condensers are right out unless you buck up for a DPA D:Facto which is worth every one of its many pennies. Which Audix mics have you got?
Old 1 week ago
  #15
Lives for gear
 
Many great things have been said, I don't have time to read it all but hear are some bullet points.

1. Find out what you are "distorting and fix that issue.

2. Get a flat "enough" speaker and test your mics response using REW, if your mic has been dropped or seen temp/humidity issues it's response could be messed up. When I take over as technical director of a job one of the many things I do is test all the mics, sure enough there has ALWAYS been one bad one.

3. Use proper mic/monitor placement

4. Most singers don't want to "monitor" a compressed signal and that won't help your feedback issues. Compression for singers is usually FoH only or in-ear in my experience.

5. If you are "clipping" something to get enough loudness you either have a messed up gain stage, VERY muddy monitors, or need more power.

6. Do you have a loud/live backline sending other "junk" into your mic?

That brings me to the point, getting a "clear" monitor mix means having a great source, post HPF/EQ monitor feed per channel, or both.

A damaged mic, wrong mic/monitor placement, muddy monitor, or other "loud" sources being sent into your mic will all cause havoc.

blessings,
mj
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