Pushing gain before feedback questions

[WynnD]

Can pushing for more gain before feedback make a mic sound bad? Or does getting the maximum gain before feedback give you the best vocal sound? I have my own opinion, but would like to hear about other people's experiences.

[RoadRanger]

 

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WynnD wrote:

 

Can pushing for more gain before feedback make a mic sound bad?

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Absolutely.

[Gregidon]

 

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WynnD wrote:

 

Can pushing for more gain before feedback make a mic sound bad? Or does getting the maximum gain before feedback give you the best vocal sound? I have my own opinion, but would like to hear about other people's experiences.

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It depends how you go about it. Simply increasing the gain shouldn't change the sound of the mic. However, if you start making drastic EQ cuts to increase the GBF, it will alter the sound of the mic, usually for the worse.

In general adding more gain on the front end (pre-amp) will make the system less noisy.

[Bobby1Note]

yes,,,, and no. (the operative words here are "before feedback"). Before feedback occurs however, you also have a potential for "bleed" from other sources, when the mic's sensitivity is increased.

Dialing gain too far back (to avoid frrdback in smaller rooms), requires "dsiciplined" mic technique, and both the performer, and board-engineer, need to be on the same page. Dialing back gain to avoid borderline feedback,usually means the singer is "right on the mic", and issues such as proximity-effect and sibilance come into play.

In a less feedback-prone room, I'll go with higher gain; primarily for the extra leeway in EQ'ing the mic for a specific "tone"..

[WynnD]

Being that I have bandmates who are willing to go that direction, what can I expect? My system is a Mixwiz into a Driverack PA (EQ'd flat outdoors.) into either ZXA1s with matching subs or into JBL-MRX 515 over Yamaha S118.

[agedhorse]

Yes, increasing system or overall loop gain can definitely decrease sound quality of the signal from a mic.

 

Since a couple of folks here don't seem to understand this concept, here's WHY:

 

A microphone is one input node in a closed loop amplification system. The other input is bleed which comes from direct and reflected sound from the speakers and room. When the loop gain is low or the phase of the reflected sound is closest to 180 degrees or the reflected sound is low in level then there is little effect on sound quality BUT when any of the above terms change, the stability of the closed loop system decreases. What you hear as a reduction in sound quality is really a decrease in stability margin and the closer the system gets to instability, the greater the impact on sound quality. Generally, anything less than between 6 and 9dB of margin is audible (depending on the environment).

 

This is all basic control loop stability engineering stuff.

[WynnD]

Thank you Andy.

[Scodiddly]

Generally if I'm working to get more gain before feedback, I'm in one of two scenarios:

 

1. Monitor wedge needs to be loud. The only EQ I'll do on the mic is a low-cut, and never above 100Hz - that voice thump may not be good in the house, but it'll make the monitor sound much bigger. The real EQ happens on the monitor mix output EQ, typically a 1/3-octave graphic. I will definitely "ring out", push the gain and start pulling down offending frequency bands, but only up to a point. If I've got more than say a dozen bands pulled down then I'm probably over-EQd. 

In this scenario doing a bit of ringing out will often make the monitor sound better, by flattening out the response peaks that are causing the first few feedback frequencies.

 

2. Corporate or church lectern mic, need to get a quiet talker up above the background noise. Here's where I would put more EQ on the mic, because I don't want to screw up the main system EQ (which also has to play music and such) to cater to the one microphone.

[witesol]

 

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agedhorse wrote:

 

Yes, increasing system or overall loop gain can definitely decrease sound quality of the signal from a mic.

 

 

 

Since a couple of folks here don't seem to understand this concept, here's WHY:

 

 

 

A microphone is one input node in a closed loop amplification system. The other input is bleed which comes from direct and reflected sound from the speakers and room. When the loop gain is low or the phase of the reflected sound is closest to 180 degrees or the reflected sound is low in level then there is little effect on sound quality BUT when any of the above terms change, the stability of the closed loop system decreases. What you hear as a reduction in sound quality is really a decrease in stability margin and the closer the system gets to instability, the greater the impact on sound quality. Generally, anything less than between 6 and 9dB of margin is audible (depending on the environment).

 

 

 

This is all basic control loop stability engineering stuff.

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thanks. a very detailed explanation indeed. In your opinion, given a reflection free environment, say a mic outside, no monitors, would you say a mic reacts/sounds different when applying more gain at input vs. acheiving the same overall level at the fader or master level?  ..I mean besides running something into clipping... I've had this discussion with a couple friends, them telling me there is a sweet spot on mic input gain. 

[Tomm Williams]

Reading the reply's and the original question, I'm a little uncertain of what exactly is being discussed. Let's just say we have a system capable of 140 db at 100' (or whatever) and I choose to run it at 60 db. I then decide to increase to 80 db, this is in effect a "push for more gain". As it still falls well below the systems capabilities, I can't see how it would have a negative impact on the "sound" of the mic. Are we talking about driving any single gain stage into clip?   

[dboomer]

Hey Tomm

 

These numbers by themselves don't mean much as they don't really address "loop gain" and also they don't necessarly relate to sonic quality.

 

I believe the sonic quality issues were asked inrelation to the eq necessary to improve GBF.

[WynnD]

You all got me laughing. Situation is that the band's PA has been my responsibility and is normally set up for 7 vocal mics and 2 horn mics and about 8 db below feedback point. (With DriveRack Pa for FOH and 2 DRPx for monitors and 6 fixed feedback filters set on each unit.) It has become too low a setting for some of my bandmates. I don't want feedback. I do want some headroom for singers who have problems pushing on certain songs. My bandmates are forcing the overall system volume up without concern for feedback. And as I've always said there is a cost to being loud or becoming louder. In this case, I don't believe any change in equipment or usage will result in any significant improvements in GBF. (If I'm wrong, please let me know what equipment will make our lives better. Then I can go to the band and find out who wants to spend some more money on gear.) There is plenty of equipment for the clubs we play in. (And there was plenty of equipment for the small outdoor gig last Saturday that covered 1/3rd the area that we cover easily in one of our larger clubs. (Probably not a large club by most standards.) There was a major difference in opinion about what is enough sound in the audience outdoors. (We weren't even covering 50' from the band.) Maximum output levels on the PA are about 124 db. (Speakers are rated 124 continuous.) Maximum output on my Leslie is 118 db. (And I only use that for solos. Aren't db meters fun?) 140 db at 100' outdoors would be 170 db at 1 meter. Don't think I've seen any single speakers that will do that outside of a tornado warning siren. (And I'm not sure they could either. That was fun.)

[StratGuy22]

Tell the singer he can't tell how loud he is from stage. Usually if you can hear yourself in the FOH, it's pretty god damn loud out front.

 

Being on stage is the worst place to try and direct a mix. Maybe have someone with a decent set of ears that the singer trusts give it a listen. If he says "ok you're way too loud" when the singer wants "more me" maybe he will believe him.

 

It's a tough spot to be in.

[StratGuy22]

Our female singer always wants lots of herself and lots of reverb, the problem is, she has to SING!! It gets close to feeding and I bring it back (monitor mix) and I know if I were to go "check 1, 2" it would blow my brains out. It's frustrating.

 

Sing dammit.

[Tomm Williams]

 

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StratGuy22 wrote:

 

Our female singer always wants lots of herself and lots of reverb, the problem is, she has to SING!! It gets close to feeding and I bring it back (monitor mix) and I know if I were to go "check 1, 2" it would blow my brains out. It's frustrating.

 

 

 

Sing dammit.

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Without a doubt, there becomes a point where all the speaker placement, processing, etc........ won't do a damn thing if the performer doesn't,.........well.............perform? I wish more performers understood the nature of how a system has to compromise so many issues. Many simply don't know how their "little" request can throw a real wrench into things. I guess that's why we make the big bucks. You guys are making big bucks at this.................right?    

[StratGuy22]

Ah....

 

The money to be made is outside the bar. The bar is fun though, and I'm helping out the scene.

[agedhorse]

There should be ~9-12dB of headroom between the point that that amps limit (rated power) and the mixer clips. The limiters subrtact gain from available headroom (limiter compliance range), so there MUST be driver electronics headroom for the limiters to operate correctly.