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gain structure with 2 mixers involved

ricosoundricosound Posts: 5
edited May 2017 in DriveRack PA2
Hi All,

I'm new to the forum and have been reading it for a while to learn how to use my DRPA2...

So far I'm quite happy with it and there results i've had , thanks also to the useful information of this forum and the people contributing.

I've been working on setting a proper gain structure for my sound system and I;ve been running into some doubts about the process. I hope someone can throw some comments on it.

How I'm running it :

Pioneer DJM600 ( with 2 Technics TT connected to it )
> output of this ( L & R XLR mains) goes into a Behringer EURORACK PRO RX1202FX line mixer ( Left from the DJM into a channel / R from DJM into another channel )
> main outs from the Behringer into the DRPA2---->then using only LEFT (mono) out from the DRPA2, low / mid / high freq are sent to :
LOW into CH1 of a QSC RMX 2450 at 4ohm/ MID into CH2 of the same amp ( 4 ohm ). This amp is powering on the LOW 2 x 15" 600W JBL 2226H---MID are 2 x 12" 450W 18Sound drivers
HIGH freq goes into a QSC MX1500a CH1 which feeds 2 x 1" 60 B&C comp drivers/horn.

Low and Mid drivers can take a bit more Watts than what the RMX2450 is able to give per channel at 4ohm but at the moment is what I have as equipment.

I am setting it up with the DJM mixer because of ease of use with turntables in the DJ station, the Behringer as a line signal mixer.

I've run the wizard set up on the DRPA2 and followed the instructions, the QSC RMX amp is in the preset list, the MX is not. None of the drivers are in the presets.
I've also run a gain structure procedure with pink noise. Did some sound testing and it seems like things are running fine. Speakers sounding loud and clear.

So..now at the gain structure doubt. On the DRPA instructions or the ones found in this forum about setting proper gain structure only one mixer is mentioned in the whole procedure.
This made me doubt of some of the steps I took to work it out. Basically I've run the pink noise signal through one of the Pioneer DJM mixer ( one the channel used for the turntables) .
Then I have used controls on the DJM ( channel gain knob , channel volume fader and master fader ) and on the Behringer ( gain, ch1 and ch2 volume faders and master fader ) to work out gain structure as per the instructions.

I've noticed that raising the gain knob or master fader pushing a signal over unity gain - 0 - on the DJM was sending a strongly clipped signal to the Behringer, which has a clip light for each channel and for the master.
Therefore the inputs meter on the DRPA were jumping into clipping. Also amps were clipping. Which make sense as the signal was too strong at that level with red lights on the mixer popping up.

At the end of this process I landed into having the Behringer line mixer fader at just about under unity gain-0- without clipping. Attenuator of the amps at about 3/4 turn clockwise.
On the DJM I can use the channel fader pretty much to the top without clipping, master fader at about 5 - 6 ( the scale printed on the fader is 0 to 10 ) which shows green lights on the meter.

I haven't tested this setting yet on a live gig , just tried at home and SPL sounded strong...actually maybe more than what I may be able to push in the Bar where I usually spin.
I will do a live test next week.

My main question on all this is , the fact that I have 2 mixers involved into setting the gain structure ...can this be as source of getting the gain level "wrong "?

I guess that as long as I am not sending a clipped signal from the DJM to the Behringer and ultimately to the DRPA2 and amps I should be running within a safe range for the speakers...?

I hope it has;t been a confusing explanation and that someone can give me some advice in case I'm doing something not right..

thanks a lot !


  • Options
    DraDra Posts: 3,777
    OK. I have been trying to understand all the information.

    I think this is what you need.

    Pioneer > Behr > PA2 > amps. Correct? I am not sue why you need the Behr mixer, but I guess that you have a reason.

    Any way.
    Bring the pioneer to just under clip.
    Bring connect to the Behr and set the channels and master to -0-.
    Set the Behr input gain to just below clipping on the Behr.
    Now, the ONLY volume adjustment, ever, is with the pioneer.

    Hope that helps, and that I was clear on you set-up.

  • Options
    ricosoundricosound Posts: 5
    Hi Dra,

    thanks for the reply...it confirmed what are my intentions on this set up.

    The connection chain you wrote is correct....

    the reason why I'musing the Bherry in the middle is as per you suggestion of having volume control ONLY on the Pioneer. As I usually have a guests selectors at the monthly night , I want them to control volume off the DJM only and set a "safe" wall at the Behringher line which they will not touch....so even if they for some reason raise value too high etc I'm not risking to send clipped signal to amps and speakers.
    hope this make sense..

    We've been running another small sound system with this set up for a few dates and it worked fine..as I was trying to work out a proper gain structure for the system I started to think about the 2 mixers situation.
  • Options
    DraDra Posts: 3,777
    So when you have the Pioneer at MAX clip, the B'ger (and down line) will not clip? That is the only way, but you loose clean signal before you reach max volume.

  • Options
    Your gear:

    # PIONEER DJM-600 (mixer)
    # BERHRINGER Eurorack Pro RX1202FX (mixer)
    # DBX Driverack PA2 (management system)
    # QSC RMX 2450 (amplifier - 2 x 750W @ 4 Ohms)
    # QSC MX1500a (amplifier - - 2 x 500W @ 4 Ohms)
    # 2 x 15� (Low – 600W each one)
    # 2 x 12� (Mid – 450W each one)
    # 2 x 1� (High)

    Initial Problems:

    1. You definitely want one more amplifier! No need to explain you the reasons…

    2. The power of the amplifier (RMX 2450) and of the woofers (2226H) is not fully utilized!

    -> Suggestion: Use channel A of RMX 2450 and set the amplifier to Mono Mix Mode (see manual p.13 & p.20). Then connect 2226H (one per channel).
    In previous case (your set-up) you got 750W total (375W per 2226H).
    In this case (my suggestion), you will get 1000W total (500W per 2226H)!

    If you follow my suggestion, than you will have to use QSC MX1500a:
    - Channel A for 2 x 12� (Mid)
    - Channel B for 2 x 1� (High)

    - Much better use of existing (amplifiers) power!
    - Much better low SPL!

    3. You use 2 mixers (pre-amplification) in-line! Completely wrong, because by interfering Berhringer (between Pioneer and Dbx) you downgrade the quality of audio signal – sound (change SNR, add noise, and many more problems).

    -> Suggestion: Completely abolished Berhringer! Then:
    - Use compressor and limiter of PA2, do necessary tests and make proper settings. I advise you to set every volume knobs (of each amplifier) to the max and then set up compressor and limiter. Thus, even if anyone set any fader (of DJM) “to the sky�, you ll be sure that any channel of your amplifiers will not clip!
    - Finally, use only volume knobs (of each amplifier) to control (0 - max) the final (desire) sound level.
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