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Mixwiz setting question.

Stephen B

I run my Mixwiz through a couple mackie 1400i power amps. The manual suggests running the main LR faders at or near the 0 level. I have always run the power amps at around 80 to 90%. If I run the main faders up at 0 this would blast out any of the smaller venues we usually play. Should I turn down the level on the power amps or continue to run the faders at a much lower level? The only other option I see is to turn down the outputs on the crossover. My question is... where would be the best place to limit the volume on my setup?
February 8, 2012 @10:12pm
jpleong

Power amps is the industry standard. Using the mixer's master fader as the volume regulator 1) theoretically (and usually practically) increases the system noise and 2) makes your mains metering useless.
If I'm in a situation where sound check and performance are going to have big unknowns for volume, I'll give myself an extra 10dB of headroom on the fader (pull back the fader to -10dBU) so I don't have to walk over to the power amps to adjust. Otherwise, it's fader at unity and set power amps so that output comes between 85-90dB c-weighted.
JP
February 8, 2012 @10:48pm
Stephen B

Thanks, that was really the only answer that made sense to me. I know the term dB but I am unfamiliar with c-weighted.
February 9, 2012 @07:29pm
jpleong

Thanks, that was really the only answer that made sense to me. I know the term dB but I am unfamiliar with c-weighted.

When you measure dB SPL there are different ways to measure it due to the nature of how the ear perceives sounds at different volumes (Fletcher-Munson curve). C-Weighting is the "flat" way to measure dB and is most useful at the 75-100 dB range (for more: http://www.sweetwater.com/expert-center/glossary/t--C-weighting) which is the target range for most "produced" events. Movie theaters are universally calibrated for 83dB-SPL(c) as an example.
One other reason why faders should hang around unity gain is that they are, by nature, logarithmic and so are most linear near the top of their travel. If you were to use them near the bottom of the travel, a slight bump could double or triple the volume potentially causing damage to your speakers or to your ears.
JP
February 9, 2012 @08:50pm
eRoland

It dose not matter if the fader is at zero on the main out if yu did not start at unity with the gain/trim at each mic pre. The gain chain starts there. I always set the gain on each channel where some where around -5 to0 on the fader is as loud as it will be on mains. So set fadr to zero and mix with gain knob first then you will not spike the speaker with loud spots in program. Moving a fader from 0 to +5 can double db on out put.
February 9, 2012 @09:08pm
jpleong

So set fadr to zero and mix with gain knob first

I know it's not what you meant, eRoland, but just to clarify: gain knob is to establish the initial signal level into the mixer. Mixing is done with the faders after the gain has been set correctly.
JP
February 9, 2012 @09:13pm
eRoland

I was trying to say. set mic channel fader to zero when you are setting gain at the top of channel. Solo channel so you can use main meter to get level no more than zero at loudest peaks. Do same as you get all channels set up. the over all gain will not spike over zero on main to keep less signal going to amps. If you do not spike over zero to the input of the amp ( around -4 on lower level stuff) it will tame overall output. It will give you a ton of head room on amp for spikes to stand out and room to drop to lower overall levels for the bulk of the signal. You can set snare or kick alittle higher and have more punch or room for any other to have extra level to stand out.
The antennuaters of the amp with not need to be turned down much if any as long as they were not turned up all the way in the first place. Staying around zero at the loudest on signal chain all the way to the amp should tame the louder program material. If this is not low enough you may need less amp and lower output speakers but I bet it will work.
Hope this is clearer.
February 10, 2012 @03:51am
Dave Burris

I think it is much more important to get your gain early in the chain (at the preamp) rather than concern yourself with where the fader sits. Set your preamp gain such that the input peak lights flicker only occasionally. I usually back off slightly from this, although A&H peak meters come on well before actual clipping. Then if you want the channel faders at zero, lower the group and/or output faders to allow you to keep your gain close to unity through the signal path. You can lower the amp input attentuators to keep the groups and output close to zero.
What you do not want to do is mess up your gain stages by cutting channel gain then boost it again at the outputs. This will only serve to increase your noise floor. Bad gain stages within the mixer are much more likely to contribute to noise than lowering the input sensitivity to the power amp with the input attenuators as necessary.
Readers' Digest version: get your gain early then maintain it throughout the signal chain up to the amp inputs. Turn down the amps if you need to, or lower the output faders. Noise introduced this late in the signal chain will be minimal.
February 11, 2012 @04:12am
TimmyP1955

I prefer to have the amps wide open, and drop the output with the master or something that's between the mixer and the amps - no one can put the system in danger by cranking the amp controls. This is especially important if your system limiters are not in the amplifiers.
February 13, 2012 @02:31am
Dave Burris

I prefer to have the amps wide open, and drop the output with the master or something that's between the mixer and the amps - no one can put the system in danger by cranking the amp controls. This is especially important if your system limiters are not in the amplifiers.

Seems this assumes the other places to raise gain are better secured than your amp rack(s).
One could just as easily state that having your amp attenuators set such that full output from the board does not exceed the power you wish to be max output is safer.
In either case, the system needs to be secured to prevent people from "accidentally" increasing the gain.
February 13, 2012 @02:10pm
yeahforbes

Seems this assumes the other places to raise gain are better secured than your amp rack(s).

I think the more relevant difference is that unauthorized changes in "the other places" are rescued by amp rack limiters, whereas unauthorized changes at the amp attenuators are not subject to any rescuing... only full-power clipping (except in the case of post-attenuator limiters inside the amps).
February 17, 2012 @05:59pm
TimmyP1955

Turning the amp attenuators down does not make overdriving the system less likely - the operator just has to push the main fader farther.
February 20, 2012 @07:16am
Dave Burris

Turning the amp attenuators down does not make overdriving the system less likely - the operator just has to push the main fader farther.

Turn them down some more! ;)
February 20, 2012 @11:52am
TimmyP1955

Turn them down some more! ;)

At some point, you'll overdrive the input stage of the amp (that's ahead of the amp control), or you'll run out of headroom in the mixer or something between it an the amp. I like to insure that the only thing that can possibly clip is the output stage of the amp. A little amp clipping ain't too bad. If something else clips too, it's nasty.
February 26, 2012 @11:19pm