Amps too powerful (where to reduce without killing gain structure)

[adessmith]

I know this is often debated, but I'm still not certain what the different approaches are, and if one approach is more widely accepted than the others.

What we have is an inexpensive Behringer Eurodesk 32 channel unpowered mixer, which feeds to a QSC GX5 amp, and then a pair of yamaha 15" club speakers. There is no expensive signal processing or anything like that. Just these 3 components. We are not going for max volume. The system is capable of producing more power than we need in the space we are in, so where do you reduce the level?

Here are all the methods I've seen (in no particular order)
1) Run your amps wide open, and regulate overal level with the master fader on your console.
2) always run your console's master output at unity, and make a reduction on your amp.
3) Unity at the master fader, amps wide open, and regulate the overall level by bringing the channel faders down (and some say to keep the faders at unity and bring down the gain at all channels)

4) (this is the way I was taught to set it up)
I play some music (white or pink noise is better) through the mixer. I set the gain for that channel so that the meter is reading around 0db and set the fader to unity. Then I bring up the master fader to a level where the output buss just begins to clip and turn up the levels on the amp (with the speakers disconnected) until the clip light on the amp just begins to light. (this way the master output on the console clips at the same point the amp does)
Then I bring my master fader back down to unity and if the level is still too high, back it down below unity.

The logic that was used when I was taught to do this was that this "synchronizes" the output of the mixer and the amp, so that you can look at your meter and tell how hard you are pushing your amp. (because those knobs on your amp are not "volume knobs"... they control sensitivity) This gives you the most headroom out of your system. However, if your amp is overpowered for your space, you end up with your master fader pulled way down and I dont think this is good for gain structure. Also, I dont like looking at the meter barely flashing 1 or 2 bars. It seems like the meter should be going to 0db durring "normal" volumes.

I realize that this method is probably great for concerts (especially outdoors) where you are squeezing every drop of power out of your system, but it seems that in most church services you dont want that much SPL.

I am not taking any official stance on how what I feel is the "right way" but I want to know what other people are doing here, and why, so I can make my own decision.

[Arlin]

Overall, I think you have a very good knowledge of all the principles involved here.

In your situation, I would keep the channel faders and masters at unity and reduce the amp knobs.
This way, you keep your resolution at the console.
Signal to noise ratio will be better because any noise that is picked up between the console and amps will be attenuated by the reduction in signal level at the amps.

[waynehoskins]

Here's what I'd generally do:

Console running at unity
Open amps up to the maximum volume you'd ever want for any event ("eleven")
Reduce output gain on the system processor to achieve desired volume

With most DSPs, that allows recallability for different configurations: normal, concert, etc., so the console meters actually mean something.

[cmchamp]

Wayne - re-read - he doesn't have any system processing
Mixer => amp => speakers

[adessmith]

Yeah, I think Wayne was just answering the question about what "other people are doing", not necessarily what I should do.

I do like the idea of using some DSP between the console and amp. However, we have a lot of other things we might consider upgrading or adding first. We have no compressors, no effects units (except the horrible reverbs built into the eurodesk), Gem Sound amp for monitors (LMOL), Speakers are Yamaha club series (S115V) on stands (decent speakers, but we want to have something more permanent), etc... The whole system needs to be replaced with higher quality and/or more suitable, components.
Our Eurodesk (SX3242FX) seems to work just fine for now, but I'm hoping one day to replace it with something a little nicer. The QSC GX5 is a rather decent amp though (probably the nicest piece of equipment we have)...

But for now, trying to make the best of what we do have.

[waynehoskins]

Exactly. In your case, turn down the amps.

[daver2]

+1 for Arlin's solution.

Keep your desk meters and faders 'sensible' and tweak the amp to get the desired volume for the venue - perhaps plus a bit more for good measure (Wayne's 11?). You can then reduce the master fader by a little from unity but it is not right down at the bottom end where your classic set-up would have you sitting.

Dave

[Johnnycat]

Mixer @ 0

Master @ 0

Amps adjusted to regular listening level for your room... Ours are between 50% and 75%

[cmchamp]

Only addendum to the above - if any of your amps are in bridged mode, check the owners manual for adjusting the input volume via the controls. Some can, some can't.

[Brad Weber]

Just a reminder since it often gets misunderstood but the level controls on an amplifier are typically applying attenuation to the input signal and are not actually controlling the potential output of the amplifier. An X Watt amplifier is an X Watt amplifier regardless of where the level controls are set, all the level controls really do is vary the input signal level required to generate that rated output.