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looking for some quick sound system validation

EBodious

EBodious

Aug 2, 2006
576
24
Iowa
#1
in one of my bands our lead singer owns a p.a. and likes to run the sound. we have gained more equipment over the last few years and the rest of us have a different view on the basics of level settings.

so, i am under the impression that the ideal way to run a p.a. is to have the individual channel gains up as high as possible without clipping, and then turn up the power amp main levels only as much as necessary to fill the room (or mix well with the drums and bass). the idea being to preserve headroom on the p.a.'s amps.

almost everyone i know agrees with this school of thought. except my lead singer. he feels the p.a. levels for mains and monitors should be run hot (66 - 75%) and the mic/keys/gtr levels should only turn up as much as needed.

it is not really a big deal, but i am curious if there is any reason for or benefit from his way of running the p.a.

thanks
 
#2
With every thing "PA" it depends. In my case:
I have always run power amps wide open.
Use the speaker processors to "tune" the PA.
Use the mixer as a mixer.
Gain structure is important, but I have found in most cases that using the mixer with the preamps running "cold", or at unity is the best way to go. YMMV.
 
#6
I PFL/solo each pre, setting them a little below unity since summing 12-16 channels. Then with the speakers unplugged, set all faders at zero and the master all the way up so the meters are just below peak/red which can be somewhere around +12 depending on the mixers max output before distortion. Then turn the amps up until the clip lights twinkle a little. Then bring all mixer faders and master fader down.
Plug speakers back in and go from there.

That way I know that the amps will clip at the same point as the mixer and know that the headroom in both are the same.

Then use the master fader to set volume for the room, not the power amps.

Ideally you want to know the headroom in each component and adjust/gain stage so that every component (Mixer, EQ, Crossover, all have the same headroom.

say the mixer has 10db above unity before clipping and going into an EQ that has 8 db headroom. I would set the EQ input level at -2db if it has input gain control, then say the crossover has 14db headroom so I would turn up the crossover input to +4db. Now every component before the amp has 10 db headroom. I run a stereo pink noise CD into 2 channels and PFL and set faders at 0. THEN I set the the master fader just under the clipping point and turn up the amps volumes to the clip point, turn it back down and plug the speakers back in, then put the volumes back up to where you determined the clip point.

I leave the hi/low freq outputs on crossover at 0. Then playing music I set volume on master fader, at lower volumes the low freq will be weak so I turn down HF crossover out to balance then bring up master fader a bit. (see fletcher-munson theory)
Every time I increase master fader volume I adjust high Freq crossover output to keep it balanced. I always cut the HF out instead of boosting LF out so i dont loose headroom as the Kick and bass need it most.
 
#7
uhdinator said:
I PFL/solo each pre, setting them a little below unity since summing 12-16 channels. Then with the speakers unplugged, set all faders at zero and the master all the way up so the meters are just below peak/red which can be somewhere around +12 depending on the mixers max output before distortion. Then turn the amps up until the clip lights twinkle a little. Then bring all mixer faders and master fader down.
Plug speakers back in and go from there.

That way I know that the amps will clip at the same point as the mixer and know that the headroom in both are the same.

Then use the master fader to set volume for the room, not the power amps.

Ideally you want to know the headroom in each component and adjust/gain stage so that every component (Mixer, EQ, Crossover, all have the same headroom.

say the mixer has 10db above unity before clipping and going into an EQ that has 8 db headroom. I would set the EQ input level at -2db if it has input gain control, then say the crossover has 14db headroom so I would turn up the crossover input to +4db. Now every component before the amp has 10 db headroom. I run a stereo pink noise CD into 2 channels and PFL and set faders at 0. THEN I set the the master fader just under the clipping point and turn up the amps volumes to the clip point, turn it back down and plug the speakers back in, then put the volumes back up to where you determined the clip point.

I leave the hi/low freq outputs on crossover at 0. Then playing music I set volume on master fader, at lower volumes the low freq will be weak so I turn down HF crossover out to balance then bring up master fader a bit. (see fletcher-munson theory)
Every time I increase master fader volume I adjust high Freq crossover output to keep it balanced. I always cut the HF out instead of boosting LF out so i dont loose headroom as the Kick and bass need it most.
Click to expand...

Pretty close to how I do it, as well. I also roll in limiters during the process. If you do it once and mark your settings, you'll be set for life....until you change out a component!

Riis
 
#9
TimmyP said:
If you run your amps full, no one can turn them up and make your limiters non-functional (unless your limiters are in your amp(s).
Click to expand...

Nobody touches my attenuators except for your's truly! I disengage the amp's built-in limiters (QSC RMX) while gain staging and re-engage once completed. I use the variable limiters on my speaker management system once I've identified the clip and sub-clip attenuator settings on the amps.

For a better understanding of the process, check out Appendix A / System Set-up and Gain Structure / pages 33-34 here:

ftp://ftp.dbxpro.com/pub/PDFs/Manuals/English/DriveRack_PA_Plus_Manual_18-0483V-B.pdf

It's geared towards dbx products but can be applied towards just about any pro audio project.

Riis
 

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