Gain control on 223xl when setting gain structure ...

miv0321

OK so I am setting the gain structure on my system which starts with a Stanton SMX 401 DJ mixer, then the dbx 223xl crossover, the 223 send highs to two Mackie SRM450 and lows to a QSC RMX 2450 amp that runs my two Mackie S410s subs in bridged mono mode.

My question is at what level do I set my gains on the dbx 223xl crossover? (for both input and out gains)

This is the only part of setting my gain structure that leaves me scratching my head. Now I did read to set all crossover levels to max, then after amp gain is set to set the gains on crossover using a SPL meter to reach the "maximum desired loudness level" usually 100-105 db SPL. I might be off here but this is how I understood it.

1st of all I do not have a SPL meter. And B. I think more than knowing the max level I need to balance the tops and bottoms. Which I guess can be done after knowing the "maximum desired loudness level".

What if I set the levels to zero on the 223 to set my amp gain? Then just back off of which ever gain (top or bottom) needs to be lowered to balance the tops and bottoms.

Honestly I if someone could tell me a step by step procedure in setting my whole system gain structure I would be a very happy camper. I know this is asking a bit much but I have several sets of instructions /procedure on setting gain structure in general and the more I think about it the more questions/uncertainty I have in setting it right. Anyhow TIA for your answers/responses.

Gadget

In any gain structure setup it's a procedure to get all the equipment talking the same language...(this means all working within the same voltage range...)
1. unplug the speakers with the amps and everything else on...
2. play either a good fullrange sound or pink noise (we offer a test CD for download here in the FAQ section) through the mixer... hopefully the PFL button routes the signal to the meters as well as the headphone output?... if so set the signal @ the channel so that you have a good strong signal averaging at least -0- vu
3. set the master output so the mixer is JUST clipping... you may need to add gain @ the input channel if necessary
4. here's the tough part with this analog crossover with no input clip indicator...with the crossover set up as desired, start @ unity-0-...and see where the amps end up... if you cannot get sufficient gain @ the amps you will need to add gain at this stage..again, the speakers are disconnected as described before...turn the amps channels up till they JUST clip (again, if you cannot get them to clip you will need to add gain at the crossover)

***remember here that the volume controls on the amps only set the input sensitivity of the amp allowing them to be used with a wide range of equipment manufacturers****

5.turn the amps down slightly so that they no longer clip
6. mark this point on the amps as the HIGHEST point the controls will ever go
7. turn down the master gains and re-plug in the speakers
8. as you suspected... balance the sound of the tops and subs by TURNING DOWN the loudest component at the amp attenuator.

Gadget

miv0321

Wow thanks for the step-by-step Gadget.

2. play either a good fullrange sound or pink noise (we offer a test CD for download here in the FAQ section) through the mixer... hopefully the PFL button routes the signal to the meters as well as the headphone output?... if so set the signal @ the channel so that you have a good strong signal averaging at least -0- vu

I need some clarification here. On my Stanton mixer each individual channel has a gain control and a LED meter. Then there is the master output level control with the master output level meter. BTW there is a cue section which includes PFL.

So my question I thought I should just use the individual channel meters and set the gain to where it is just green, maybe a little yellow flicker yellow but definitely not red (BTW there are no numbers on individual channel meters i.e. -10, 0, +10, etc). Then set the master level to just clipping. Is this the same as you prescribed in step 2?

Somewhat related, do you think it is safe to play pink noise through my active Mackie SRM450's since there is no way of cutting the sound to adjust the gain on active speakers? I normally have never gone past 12 noon on the speakers level control and don't expect that to be much different. I just figured might as well set the speakers levels in the whole gain structure equation also.

Thanks again!

Gadget

two Mackie SRM450

DAMN... sorry... too many threads going on at once... ya leave the 450's set @ 12 o'clock and try doing JUST the subs to begin with and see if you can get some kind of parity with the subs...

quote]do you think it is safe to play pink noise through my active Mackie SRM450's since there is no way of cutting the sound to adjust the gain on active speakers?[/quote]

Sure there is... the crossover gain for the Hi outs...

g

miv0321

Right, but I meant set the gain on the active speakers like I would set the gain on the amp that powers the passive subs. With the subs not connected to the amp ... no sound. 12 noon is where I will leave the 450's, and adjust the subs on the crossover.

Oh, was that a YES to my question about step 2 in your gain set-up scenario?

One LAST thing (I think ). How does the dbx 223XL INPUT gain play into all of this? I assume also start at 0, but then when and why would I adjust higher or lower? When the low out put gain is cranked up but still not clipping the amp when it is cranked also, for example? or vice versa maybe, the low output gain is barely up and clips the amp with barely any amp gain up. I think I answered my own question here. But confirm if you can.

Thanks!

Gadget

So my question I thought I should just use the individual channel meters and set the gain to where it is just green, maybe a little yellow flicker yellow but definitely not red (BTW there are no numbers on individual channel meters i.e. -10, 0, +10, etc). Then set the master level to just clipping. Is this the same as you prescribed in step 2?

Yes, with little else to go on that would work fine...

4. here's the tough part with this analog crossover with no input clip indicator...with the crossover set up as desired, start @ unity-0-...and see where the amps end up... if you cannot get sufficient gain @ the amps you will need to add gain at this stage.

Here I specified to start at -0- (12 o'clock) on the input gains on the crossover... this is considered the unity position and for the life of me I don't understand where a signal to noise can be "fixed" when there is so much difference in the outputs of todays equipment... but I guess it's a starting point...and as I said, if you CANNOT get the amps to clip then ADD gain there on the crossover.. however, if you are having to set the amp attenuators too low... then turn DOWN the gain controls on the xover... that is what they are there for...

Right, but I meant set the gain on the active speakers like I would set the gain on the amp that powers the passive subs.

This is going to be difficult since the 450's have a non defeatable compressor in the amp section....the compressor will start to squash the gain and you won't know when the amp ACTUALLY starts clipping...

Looks like you have the basics though...

Gadget