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Properly Setting Gain on a Crossover


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More PA newb type questions from Howie. . .

 

I think I finally have my new PA ready to go. A&H Mix Wiz to a DBX 223xs. The highs will go into the QSC GX5, then onto my Yorkville NX35s. The lows will go directly to the powered Yorkville LS200Ps. My new EWI mixer case/rack will be here later this week. We'll be using it this weekend for the first time.

 

The user guide for the A&H Mixer has plenty of details about properly setting up the gain on each channel and the overall output. No worries there.

 

My question comes about how to properly set up the gain of the crossover, and then the gain settings on the GX5. There's not a lot of info in the manuals. Any advice on how to properly set this up?

 

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Howie22 wrote:

My question comes about how to properly set up the gain of the crossover, and then the gain settings on the GX5. There's not a lot of info in the manuals. Any advice on how to properly set this up?


Simple answer:

Set the GX5 and sub fully up. Set the high output of the 223 on "zero" and use your ears to set the low output to taste, probably somewhere between "zero" and full up.

I'm sure there will soon be more complex answers posted here to choose amongst if you are so inclined wink.gif.

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dboomer wrote:

 

You need to know how much gain the amp and the sub have before you can begin to answer the question. So how much?

 

 

 

Mixer puts out +4dBu set at a meter reading of -0-, with a total of +26dBu

 

Input level on the power amp is +24dBu max.  Input sensitivity is +4dBu (1.2 Vrms)

 

Input sensitivity on the sub is +4 when level is set at -0- (recommended level). 

 

Max input gain on the crossover is +21dBu

Max output gain on the crossover is +20dBu

SNR of the crossover is +4dBu

 

 From what the Rane site said, I should unplug the speakers, put a pink noise signal through the mixer until the meters read their max unclipped, turn the output on the crossover to max, and then set the power amp until it just begins to clip. 

 

It then describes using pink noise to set the crossover level until a max SPL for the room is reached. I don't have a meter, so I assume I will set to -0-, see how it sounds playing music, and adjust?

 

 

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As Andy said but with a twist.

Have the QSC amp input sen. knobs all the way up but have it turned off with the speakers unplugged and the crossovers HIgh out and Low out set all the way down.

Put your music on through the channel. Make sure the eq is set flat on that channel and on your house eq to start. Run the channels gain so -0- is showing on its channel strip input meter and put the channel fader to -0- as well. Run the master up so you get +4db on the master out. Have just the subs on with the subs input gain at +3. Crossovers inputs set as Andy stated to + 3 I believe. Now turn the crossovers Low Output up until the subs start to limit and leave it. Pull the channel fader down and turn on the QSC amp and plug the speakers in.  Turn the fader up some so the subs just start to work at a healthy but not too loud of a level. Now turn the HIGH OUT KNOB up on the crossover until the tops blend with the subs. Don't have too much sub "sound" at a lower level as they will tend to overpower the tops when you get cranking. Just have a solid bottom. Now go to the house eq ( if you have one ) and eq the system to sound the best. Last if needed eq the input channel.

Overall this will mean when your board is Around +4dbu on its output meters your subs will be close to maxed out and your tops will blend with them. Should the QSC amp limit before the subs then you may have to bring them down some but I don't see this as happening. I see your subs as the limiting factor to this system thats why I set unity with them first then added the tops.

Dookietwo

 

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crossover input set to 0, low out set to +3dB to account for the rough difference in sensitivity.

If either the subs or tops limit earlier when everything is eq's and fed proper program material, that just means that there's not enough rig for the gig in that section of the PA.

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