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Live PA problems
Posted: Mon Oct 18, 2010 12:36 am
by redxdown
Hello everyone,
I just played a live show recently and had a crazy tough time with feedback on my guitar and vox running through ableton.
first off I'm trying to tackle the vox. the sound man at the venue said he normally does not gate the vocals but I have always had to using ableton. My signal path is as follows:
Shure SM58 into a gate at threshold of about -20 db.
THen into an EQ which at about 3k I am filtering out a few db and again above 10k I roll off the high end.
Signal then enters two compressors, the first has a fast attack, 9:1 ratio and 7.2db Knee, the second has a slower attack and a softer knee with similar ratio.
Then the signal goes through various effects, A utility to notch up volume, saturator with some drive to give the vocals some warmth, reverb etc etc.
On my master I am also running a vintage mastering plugin of ableton's.
Anyways, does anyone know where my setup is faltering. For the show I had to kick up the threshold on the input gate as well to try and curve the feedback. You can imagine what that did to the vox!
thanks to anyone with live PA knowledge out there. I would love to get the setup to a point where I don't need a gate.. but wondering if this is possible going through Live.
thanks folks,
donal.
Re: Live PA problems
Posted: Mon Oct 18, 2010 12:48 am
by Winterpark
the problem is that you've got too much compression going on your vocals, which is making the foldback feedback.
Re: Live PA problems
Posted: Mon Oct 18, 2010 2:35 am
by luddy
redxdown wrote:
Signal then enters two compressors, the first has a fast attack, 9:1 ratio and 7.2db Knee, the second has a slower attack and a softer knee with similar ratio.
right (what "am" said).
compressor ratios are multiplicative rather than additive, so 9:1 followed by 9:1 is is 81:1. Essentially infinite compression ratio. If you have makeup gain to offset that (which you must, if you're gonna hear the vocal) then you're really asking for it with that kind of ratio. What happens is that the PA+EQ has a frequency response spike somewhere -- say 2500Hz. So a bit of sound goes through the mic at that frequency, comes out amplified a LOT, hits the mic again, comes out amplified even more, etc. etc. For a live vocal, a compression ratio of 3:1 or something along those lines is a lot more reasonable, and a mic with a tight pickup pattern is a big help. Monitor wedges should be well out in front of the vocalist and the mic should be kept pointed backwards (butt end toward the monitor wedges) all the time.
The gate is not the problem IMO. If the gate closes, that can't make the feedback worse, and if it's open it's like it's not there. I'd work out the problem with the gate disabled. Then putting it on if you want it should have no effect.
hth,
-Luddy
Re: Live PA problems
Posted: Tue Oct 19, 2010 4:22 am
by redxdown
thanks "am" and "luddy" so very much:)
see some of my comments below;
luddy wrote:redxdown wrote:
Signal then enters two compressors, the first has a fast attack, 9:1 ratio and 7.2db Knee, the second has a slower attack and a softer knee with similar ratio.
right (what "am" said).
compressor ratios are multiplicative rather than additive, so 9:1 followed by 9:1 is is 81:1. Essentially infinite compression ratio. If you have makeup gain to offset that (which you must, if you're gonna hear the vocal) then you're really asking for it with that kind of ratio.
I wish we had the ability to post the jpg's of our signal chain here directly so I could show you what's happening after the compressor. Is there that capability without having to load the image to a http address?
What happens is that the PA+EQ has a frequency response spike somewhere -- say 2500Hz. So a bit of sound goes through the mic at that frequency, comes out amplified a LOT, hits the mic again, comes out amplified even more, etc. etc. For a live vocal, a compression ratio of 3:1 or something along those lines is a lot more reasonable, and a mic with a tight pickup pattern is a big help.
When you say a mic with a tight pick up pattern, what exactly do you mean?
The reason I was using such hard ratios, I think, as I can't rightly say now, was that the vox in the studio sounded really forward with this setting! It really brought the vox to the front of the mix. So from what you're saying I guess I could get the same if I dropped the ratio to 3:1, and then that begs the next question: If I'm using two compressors, I should have each set to about 1.5:1?
Monitor wedges should be well out in front of the vocalist and the mic should be kept pointed backwards (butt end toward the monitor wedges) all the time.
yes, aware of this one, but as you've both determined, the issue is more than likely with the infinite ratio of the compression units combined.
The gate is not the problem IMO. If the gate closes, that can't make the feedback worse, and if it's open it's like it's not there. I'd work out the problem with the gate disabled. Then putting it on if you want it should have no effect.
sound advice for sure!
thanks,
donal.
hth,
-Luddy
Re: Live PA problems
Posted: Tue Oct 19, 2010 7:23 am
by Winterpark
you can post images... just hover your mouse over the "Img" box, and it explains how to do it... you just have to upload the image online somewhere.
re: compression in productions, vs. live.
they really are very different beasts. In studio/production you can afford to over compress things like vocals to get that upfront sound, or make it breathy, or whatever you want to do... but in live situations, it simply doesn't work like that.
You're much better off sending a dry signal to your sound engineer, and leaving it up to them to do all the processing.
If you have some specific fx you want to use, like a time-synced delay, then i'd probably set it up so that you're sending a dry signal to your sound-person and a wet fx mix on a separate channel... i'd never include compression or limiting on this... just things like vocoding, reverb, delays, chorus maybe...
I'm not sure of what you're routing audio-wise or what sound card you're using, or even if you have a mutlti-out soundcard... but i'd recommend setting it up in a way that you can give some degree of control to your F.O.H. engineer, because they can hear what it sounds like out the front, and you can only hear what it sounds like on stage.
Re: Live PA problems
Posted: Tue Oct 19, 2010 1:34 pm
by redxdown
Cheers AM,
it's the online thing that stops me with the images.
Anyways, it's not that important
Yes, I agree, if there is an engineer that sounds like a plan. My last show had one of the best engineers in the city and I had him stumped but then again he didn't get to look at my signal chain of compressors. He'd have noticed it straight away.
My S/C is the presonas Firebox. I do have the capability of sending the vox out, one dry and one wet. Assuming I don't have to do the same with the guitar I should be fine with that soundcard. Otherwise I'll have to upgrade to a larger beast.
One more thing though, What if I am doing my own PA, no front house man? Can i just cut back on the ratios as suggested? I know rooms will vary so I'll have to try and make some compensation for that on the fly before a gig. i.e. if the room is very wet then I'll have to cut back on reverbs and delays.
Cheers for the help,
Donal.
am wrote:you can post images... just hover your mouse over the "Img" box, and it explains how to do it... you just have to upload the image online somewhere.
re: compression in productions, vs. live.
they really are very different beasts. In studio/production you can afford to over compress things like vocals to get that upfront sound, or make it breathy, or whatever you want to do... but in live situations, it simply doesn't work like that.
You're much better off sending a dry signal to your sound engineer, and leaving it up to them to do all the processing.
If you have some specific fx you want to use, like a time-synced delay, then i'd probably set it up so that you're sending a dry signal to your sound-person and a wet fx mix on a separate channel... i'd never include compression or limiting on this... just things like vocoding, reverb, delays, chorus maybe...
I'm not sure of what you're routing audio-wise or what sound card you're using, or even if you have a mutlti-out soundcard... but i'd recommend setting it up in a way that you can give some degree of control to your F.O.H. engineer, because they can hear what it sounds like out the front, and you can only hear what it sounds like on stage.
Re: Live PA problems
Posted: Wed Oct 20, 2010 6:15 am
by Winterpark
redxdown wrote:
One more thing though, What if I am doing my own PA, no front house man? Can i just cut back on the ratios as suggested? I know rooms will vary so I'll have to try and make some compensation for that on the fly before a gig. i.e. if the room is very wet then I'll have to cut back on reverbs and delays.
If there is not soundperson, then you'll have to just judge it yourself... you're right about cutting back on the reverb in a 'live room' like a big hall with lots of reflective surfaces.
Using that much compression is always going to be an issue live. You could borrow a powered wedge, or even crank your studio monitors, and test it out beforehand? see what levels you can actually get to before it feeds back.
Another solution would be to get in-ear monnitoring, and cut the stage sound out totally... but you could still run into problems with the FOH feeding back depending on the room size.
hope that helps.
Re: Live PA problems
Posted: Wed Oct 20, 2010 8:23 pm
by redxdown
that's great AM,
ya, I'll work on lowering the ratios in compression to be safe
Cheers,
redxdown.
Re: Live PA problems
Posted: Sun Oct 24, 2010 12:24 pm
by luddy
redxdown wrote:
When you say a mic with a tight pick up pattern, what exactly do you mean?
I mean, say, a hypercardiod rather than cardiod pickup pattern. I.e., it picks up sounds only that are very close to the mic and very much in front of the mic, nothing from the sides or rear. Some handheld mics like a KSM9 have an adjustable pickup pattern; this feature is above all for feedback problems.
The reason I was using such hard ratios, I think, as I can't rightly say now, was that the vox in the studio sounded really forward with this setting! It really brought the vox to the front of the mix. So from what you're saying I guess I could get the same if I dropped the ratio to 3:1, and then that begs the next question: If I'm using two compressors, I should have each set to about 1.5:1?
Well, hmm. First, I agree with 'am' when he says studio and live are different. Your singer won't sing the same way for one thing, most singers tend to sing louder and with more dynamics on stage, just because it's a noisier more exciting setting, and maybe they can't hear themselves as clearly as they'd like. I use just one vocal compressor for live show, seldom more than 3:1 ratio, and keep the threshold high enough that it's not compressing the vocal all the time. Set a long, soft knee if you want to hear some gentle compression all the time. A common reason people get feedback through vocal mics when using compressors is that the threshold is set so low that the mic attenuates a LOT when the singer is singing, but when they stop the gain soars through the ceiling (as the compressor releases) and the background noise / non-singing is amplified like crazy through the vocal mic. The higher the ratio, the worse this effect.
Personally I think staging compressors in a live setting is a bit of overkill and is asking for trouble. What I have done on occasion is to put a comp with fairly high threshold and 3:1 ratio, followed by a limiter, also with pretty high threshold. Limiters are nice for live vocal mics because they clamp down on all kinds of bad noises (pops etc.) Again, the limiter should not be working most of the time.
-Luddy
Re: Live PA problems
Posted: Sat Jun 11, 2011 12:14 am
by redxdown
well lads,
I'm finally getting ready for the next gig and reading all your words of advice from the thread here on compression and live vox.
It's great to read over again. AM you mentioned in one of your posts:
"If you have some specific fx you want to use, like a time-synced delay, then i'd probably set it up so that you're sending a dry signal to your sound-person and a wet fx mix on a separate channel... i'd never include compression or limiting on this... just things like vocoding, reverb, delays, chorus maybe..."
As I use delays and reverbs alot with my vox and adjust parameters within the both effects I'll need to be able to control these.
Maybe what I could so I have a dry channel and send the dry to send this also to a wet channel and then mix it back in with the original dry and then sending it to the board. reason being that I want to be controlling the amount of washed out delay's reverbs the audience hear. If I leave it to the sound guy he won't know what I'm aiming for.
Make sense?
redxdonal.