How many compressor channels in your rack?

C

Cazzbar

Throbbing Member
I've been having a few puzzlements going around in my head lately about the number of compressors I need and how to set them up... this is mainly a question for a live set up really, but would be handy to know for outboard mixing as well

In my band everything comes out of the PA (vocals, guitar pods, electric keyboards) and sometimes the drums will be mic'ed up too.

I would like our 3 vocal mics to have compression, plus ideally have room for snare and kick compression when they're also mic'ed (and maybe guitar compression) and it would be nice to have the whole stereo mix safely limited (as we had a little fire incident on one of our speakers recently :rolleyes: although no-one died)

So this adds up to about 9 compressed channels and as the units normally have 2 channels... I would need 5 units?! :eek: quite expensive and would easily overflow my 6U portable rack, which already has EQ and Verb.

I've been looking at the DBX Quad units, a couple of those would almost do the trick, but these typically don't come with any gating which the dual units have.

I was wondering if there was a few ways of cheating, e.g. we don't tend to sing at the same time so maybe all our vocal mics could be grouped and sent to the same compression channel... ?

Or is the reality you just have to have a rack full of expensive compressors!
 
Cazzbar said:
I've been having a few puzzlements going around in my head lately about the number of compressors I need and how to set them up... this is mainly a question for a live set up really, but would be handy to know for outboard mixing as well

In my band everything comes out of the PA (vocals, guitar pods, electric keyboards) and sometimes the drums will be mic'ed up too.

I would like our 3 vocal mics to have compression, plus ideally have room for snare and kick compression when they're also mic'ed (and maybe guitar compression) and it would be nice to have the whole stereo mix safely limited (as we had a little fire incident on one of our speakers recently :rolleyes: although no-one died)

So this adds up to about 9 compressed channels and as the units normally have 2 channels... I would need 5 units?! :eek: quite expensive and would easily overflow my 6U portable rack, which already has EQ and Verb.

I've been looking at the DBX Quad units, a couple of those would almost do the trick, but these typically don't come with any gating which the dual units have.

I was wondering if there was a few ways of cheating, e.g. we don't tend to sing at the same time so maybe all our vocal mics could be grouped and sent to the same compression channel... ?

Or is the reality you just have to have a rack full of expensive compressors!
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I've been sending all vocals to a sub buss and using 1 compressor on the insert. Seems to be working pretty well even when there are 3 of us doing harmonies.
 
My compressors currently consist of:

Distressor EL8-X (2)
DBX 162
DBX 903 (2)
Aphex Expressor (2)
Aphex Compellor
JoeMeek SC 2.2
ART PRO VLA
MXR 136 dual comp/limiter

And a DAV BG-4 on order.

I don't necessarily use them all at once on the same mix. The variety is for the purpose of having tone color choices when mixing down.

Also, I don't use these for PA type work, this is strictly studio stuff. So a couple DBX quads might work just fine for your live work.
 
You Might Try Hooking up your Compressor to your Mixers FX Send/Return and then you will be able to add Compression useing the FX Mix Dial on the Mixer, The Problem with that is you would be useing the Same Type of Compression on all Channels that you use Compression on.....

Cheers
 
All of my live racks have between 8 and 20 channelsof compression. I also have at least 4 dedicated gates in some and 12 in others. Of course, I also run a rental company and we do some bigger shows. Most of my racks are set to accomadate on set of comps and gates for the headliner, and one for the other bands.
 
Thanks for the responses, as always most appreciated.

You've confirmed that if I need to compress everything properly I'll need a dedicated compression channel (and therefore a dedicated rack of compressors!) for everything that needs compressing... (this sounds obvious but when there's no one else around to speak to this is a big help)

(and if I want to compromise a little and group channels I can, and I appreciate live guitar compression is a luxury, and I will definitely check out the Presonus ACP88)

As far as the limiting is concerned, I think everyone would like their systems to limit with as little distortion as possible... is PeakStopPlus from DBX the way to go? (yep, I've been reading their advertising blurb) or are there equally eloquent, and cheaper! limiting solutions available, especially when limiting/speaker protection is the main requirement

Cheers
 
Cazzbar said:
As far as the limiting is concerned, I think everyone would like their systems to limit with as little distortion as possible... is PeakStopPlus from DBX the way to go? (yep, I've been reading their advertising blurb) or are there equally eloquent, and cheaper! limiting solutions available, especially when limiting/speaker protection is the main requirement

Cheers
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Personally, I don't think a bit of distortion in a PA limiter is a bad thing for the most part. Because you should turn it down if you are hitting your limiter constantly. It means you have gone too far. If you aren't paying attention to your levels, there's nothing like the crunch of a limiter to wake you up.

Limiters often give people a false sense of security, as they believe a limiter will protect their system over time. It should be used to catch peaks and momentary lapses of control. Driving your system into a constant 3-6db of limiting could be as bad as not having any at all. It also means you probably don't have enough PA.

Anyway, I like the Aphex Dominator for PA limiting. Brickwall and clean. They pop up on ebay a lot. I got mine for $300 USD. The dbx stuff works, but can definitely be overshot. That's when stuff gets by the limiter.
 
I do sound for a local rockabiilly band. We usually use about 20 mixer channels; drums are run through a submixer and the main mixer is a Mackie Onyx 16 channel. The pres are pretty smooth. Effects are minimal.

I have a four space rack in which I'm using a Lexicon channel for light compression on up to five vocals through one aux send, another Lex channel with a short delay for a couple of the same vocals and set up through a second aux send. The Lexicon gives me very nice and controllable effects. I may run a bit of the acoustic instruments through the compressor as well, but not much. The musicians all have stage amps and most of what I'm doing with so many channels in the mix is to achieve a balance with vocals.

I run a mono main mix and route that through a channel 1 of a basic 31 band graphic eq and then driectly into a BBE Maxcom; then to Mackie active cabs. I run just one monitor mix and that is run from an aux send through channel 2 of the eq and channel 2 of the Maxcom. The Maxcom allows me to add a little presence to the whole mix if needed, but I find the real benefit of having it at the end of the chain is (a) a second line compressor means all the compression can be gentle instead of harsh, and (b) the Maxcom works as a pretty capable optical limiter. Other than damage I did to a switch before I was using a proper rack, the BBE has been trouble free and lowers my stress level in a live circumstance. Just don't forget to turn it off when you're trying to sound the room!

I had a pretty funny instance where I had left it engaged and was scratching my head because I couldn't get the system to feed back gradually. It was nothing and then all hell broke loose. Then I saw the limiter was engaged - and had been working pretty hard I expect. I shut it off and looked around to see if anyone had seen me being a such a wetheaded neophyte. Nope. :D
.
 
Personally, I don't really like limiting a PA much at all. When I do, I use the multiband limiters in my BSS Omnidrives. Sadly though, that is a pretty expensive way of limiting a PA. In the end, it is much better to know where your limits lie than just engage a limiter. Limiters often make people seem too portected and it is too esay to let stuff hit them constantly. If you are pushing into your limiter there is a good chance that you are damagin your system even more than not using one. By constantly hitting your limiter you may be putting too much pressure on your speakers by not giving them any sort of a breal with dynamics. A few peaks here and there should not hurt anything. It is also extremely important that you have your limiter set properly to your amps. If you set the limiter to activate too soon, than its really easy to keep your mix at the limiter which affects the way it sounds and how hard the speakers are working. If you set it too late, than you have a false sense of security. To me the most important thing is to watch how the amps are taking things, and secondly to listen to how the speakers are handling it all. Typically I run soundchecks extra loud. This gives me a chance to watch the amps, listen to the speakers in an empty house, and hopefully find the system headroom should the room fill up later and I need to push a little.
 
Good advice.

One of the things I do in sounding a room is get my graphs pretty set and then drop them all down so I have little if any boost, making up for it in the gain. The other thing is to do the sound check without the limiter and then engage it.

The challenge for me that I expect makes the limiter help so much is that the volume will change through the evening as more people get stoked and the place fills up. By the end of the evening we are really cranking and it still has to sound crisp and clear - and be in control. So the limiter starts working about halfway through the second set when I've got my hands full as it is. It keeps my stress down; at least the system is not going to start getting jumpy on me.

I do find that I change the relationship between channel levels, subs and mains a few times during the evening to keep everything under control as things heat up and as the setlist geats rowdier. I seem to be scanning every single control and adjustment all evening. Everything. Mr. Geek. :D
 
boingoman said:
Driving your system into a constant 3-6db of limiting could be as bad as not having any at all. It also means you probably don't have enough PA.
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The crux of the biscuit, Boingo!

If you are hitting the limiter constantly, you aint got enough 'tosterone in your PA.....
 
I agree, just the reason I was interested in limiting is because we smoked one of our monitor speakers at a gig a few weeks ago.... and I wasn't sure why until last night. Too hot a signal obviously, but I was especially careful on the night in setting the correct gain for each channel (using the PFL mix and peaking at or around '0' on the meters) and the master meters during the performance were also peaking at or around zero and nowhere near clipping.

But I just noticed on my mixer I also have a PFL button on the overall monitor faders, and these told my dreadful mistake! I've always stupidly assumed the monitor channel dials were calibrated in the same way as the master channel faders (i.e. 3/4's up on the master fader takes you to '0'... but 3/4's around on the monitor dials takes you to about +6db! :eek: so my monitors had little to no headroom, and I do remember seeing the monitor peak indicators flash a few times, but as I was playing as well I just errmm kinda ignored it :rolleyes: )

I've always felt in good control of the main mix and never felt I needed a limiter there, so hopefully now I can be in control of the monitor mix as well, and not 'need' a limiter... but as I've no constant light-bar metering of the monitor mix like the master mix (only a little 'peak' light which I could spot too late) it may be a good safeguard.

(This is a good place to chat, it's saved me a good few pounds on monitor speakers me thinks!)

Also in my search for compressors I've read nothing but glowing reviews for the Alto Cleo 8.0, eight channels with gating and brick wall limiting which appears to be a match for the Presonus ACP88 and more affordable
 
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:D Nice job frying the monitor. You haven't lived until flames come shooting out of one of your speakers. I'd still be careful, your speakers may still have blown unless you realized the limiter was working in time.

Side note- "Correct" gain structure is a matter of preference or situation, many times. Me, I set my faders at unity and set my initial mix with the gain controls.

Here's the logic:

I have a visual reference to use. If some dumbass moves a few faders, it's easy to tell by looking. Also helps if you have to make adjustments on the fly. You know where you started, and where you are.

If everything is at zero at the inputs, it's likely you will have to drop some faders to make the mix right. So you have boosted a signal only to cut it with the fader.

The mixer circuitry is running close to unity except for the preamps, which is hopefully the quietest and best-sounding it will be.

I can run my power amps wide open. This is about noise too. Most likely your amp is the noisiest thing you have. Running it with the inputs attenuated brings up the noise floor.

I have done it the way you do on occasion, when monitors run off the same board as FOH and I need more juice in my monitor signal. But that rarely happens, and usually just for a channel or two. And once or twice, I had to use a mixer that had so much noise I had to goose the inputs almost to clipping just to get above the hiss of the thing. These days the mixer is not likely to be the chief source of noise.

Anyway, good luck. :)
 
I've told everyone we had flames coming out of the speaker (just to sound more rock 'n roll lol) but to be honest there was just a serious amount of smoke! But we use all active speakers now instead of power amps, and knowing there was electricity being pumped into a speaker which was about to flame scared the **** out of me!

I managed to uplug it, but under pressure I was unable to stop the overall monitor peak lights from flashing red (I didn't want to touch the gains as I spent a long time getting the main mix right, and I didn't realise the unity gain position was half way on the monitor dials :rolleyes: ) so I unplugged the other monitor for safety reasons (this obviously meant we couldn't hear a thing we were playing and were dying on our ars*s !). Halfway through the set I turned one of the main FOH speakers around to face us, we were back in business :cool: and interestingly it become clear our vocals were being drowned out, I easily fixed that problem and we had a great 2nd half set.

So next time I may not run a monitor mix, just feed the main mix into the monitor speakers (minus the bass maybe as we've two subs) it was a great feeling knowing you're hearing what the audience is hearing. If you have a soundman who can manage both mixes then great, but when you're doing it all yourself and performing... it's very difficult.

We never had a limiter, I'm kinda glad now because I've learnt from my mistake... a limiter would have just papered over the cracks of my settings

Interesting comments on setting all your faders to unity, and then adjusting the gain to get the mix... I used to do that a lot but was discouraged by all the 'text book' manuals saying the PFL method was the best for the signal noise ratios. I may go back to doing it your way now as it does make sense.

Also you then say you're able to run your power amps "wide open"... I'm not sure what this means, the gain on my active speakers run from the usual minus infinity, to unity at half way, to about +9db fully clockwise... does wide open mean unity or fully clockwise! This clearly would have a big impact on the amount of individual gain required for each mixer channel. I currently set all my active speakers at unity.

Thanks for your comments!
 
Minion said:
You Might Try Hooking up your Compressor to your Mixers FX Send/Return and then you will be able to add Compression useing the FX Mix Dial on the Mixer, The Problem with that is you would be useing the Same Type of Compression on all Channels that you use Compression on.....

Cheers
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you wouldnt want to send compression to an aux. aux's are for effects. mixing in compression like that wouldn't do much, if anything, to the level of the signal.
 
Cazzbar said:
Interesting comments on setting all your faders to unity, and then adjusting the gain to get the mix... I used to do that a lot but was discouraged by all the 'text book' manuals saying the PFL method was the best for the signal noise ratios. I may go back to doing it your way now as it does make sense.
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Both ways have their benefits and drawbacks. And both strive to reduce noise to the minimum. That's the basic concern. If the amount of noise is acceptable, and these days gear is much quieter in general, I don't think it matters which method you prefer.

One problem you can run into with doing it the way I prefer is that if you run out of juice on a channel, you have no choice but to turn up the gain. If you also run monitors from FOH, you have to do this annoying dance of turning the monitor sends for that channel down while turning the FOH gain up. :mad:

ps- Rumor has it this method originated in theater work. True or not, many theater mixers work this way, as for them having a visual zero point to return to is critical.

Cazzbar said:
Also you then say you're able to run your power amps "wide open"... I'm not sure what this means, the gain on my active speakers run from the usual minus infinity, to unity at half way, to about +9db fully clockwise... does wide open mean unity or fully clockwise! This clearly would have a big impact on the amount of individual gain required for each mixer channel. I currently set all my active speakers at unity.
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For a traditional power amp, wide open would be the same as the unity setting on a powered speaker. So yes, the extra input gain could help you with a weaker signal from your board. You could just as easily turn up your monitor send from your board, though. It's all kind of a balancing act, choosing where to boost or cut signal to give you the least amount of noise while making the system easy to use for your situation and preferences.
 
Thanks boingoman, that's the first time I've seen in writing my long term confusion and frustration when setting up a mixer! expecially when running two mixes, it's like the uncertainty principle or something, the more control you have on one mix, the less control you have on the other.

Yep, if you set the gain as suggested by the text books then you have to start attenuating on the faders for the mix (and maybe even boosting a channel if you've spent ages getting everything else just right and you haven't the heart to start reducing everything) Or you set all the faders on unity, then mess up the monitor mix when you want more gain.

It's cool knowing it's a balancing act rather than always thinking I must be doing something wrong here, I will feel more confident the next time I have to run two mixes.

Cheers
 
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