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[Alan Chavis]

Hello,

I play in a six piece pop/rock band and we are working with a relatively new PA system.  We generally play small restaurant venues.

I'm hoping to get some advice on configuring our system to use an aux-fed sub-woofer.

Here's our input list:

Kick
Snare
Drum Overhead 1
Drum Overhead 2
Bass Guitar
Keyboard
Acoustic Guitar
Electric Guitar 1
Electric Guitar 2
Vocals 1 - 5

PA Equipment:

Allen & Heath Qu-16 Mixer

JBL PRX-712 Tops (2)
FREQUENCY RESPONSE (±3 DB) 55.7 Hz – 18.2 kHz

JBL PRX-715LF Subwoofer (1)
FREQUENCY RESPONSE (±3 DB) 44 Hz – 91 Hz

All performers are using in-ear monitors, so there are no floor monitors.

My plan is to use Mix 9 as a sub-woofer mix.  I'm thinking I only need to send Kick, Bass Guitar, and possibly Keys to the sub.

Questions:

1.  Should I roll off the lows on the main mix to the PRX-712s using the Qu-16's GEQ?  The sub-woofer's internal crossover is at 90Hz.  The Qu-16's GEQ has bands at 31, 40, 63, 80, 100, etc.  What amounts (if any) should I have of these in the main mix?

2.  Will I still need some amount of kick in the main mix for the higher frequency attack sounds?

Any other suggestions on how to configure this setup would be greatly appreciated!

Thanks!

Alan

[John Penkala]

Questions:

1.  Should I roll off the lows on the main mix to the PRX-712s using the Qu-16's GEQ?  The sub-woofer's internal crossover is at 90Hz.  The Qu-16's GEQ has bands at 31, 40, 63, 80, 100, etc.  What amounts (if any) should I have of these in the main mix?

2.  Will I still need some amount of kick in the main mix for the higher frequency attack sounds?

Any other suggestions on how to configure this setup would be greatly appreciated!

Thanks!

Alan

#1   Not Necessarily. The speaker should already have a high pass crossover filter when used with a sub.
#2   Yes, you should send everything you want in the main mix to the main mix and use a post fader aux send to the subs.

FWIW, The QU16 probably has a good sweepable high pass filter on each channel. Therefore, I don't think the benefits of running the subs on an aux are going to be as great as if you had a fixed HPF at 80 or 100hz.  Use your ears.

[Alan Chavis]

#1   Not Necessarily. The speaker should already have a high pass crossover filter when used with a sub.

My understanding was that the crossover is in the sub on these.  The sub has a high pass / full range switch for the pass thru connections.

Normally I run the main output into the sub first, then connect the outputs of the sub to the tops.

Do these tops have a crossover in them?

[Debbie Dunkley]

JBL PRX have the crossovers in the subs.
You are best to utilize the crossovers in the subs and send everything else to the tops -ie NOT use aux subs. It is by far the easiest and most effective way to use your system and is how it was designed to be used.  Any use of aux subs in this particular senario would get more complicated as the tops have no crossovers and you would have to send full range to them - or use an external crossover.
However, if you are adding an extra powered sub - then aux fed would be simple as the tops have already been taken care of.
QSC k series for example have the crossovers in the tops and this would work better with aux subs.

[John Penkala]

My understanding was that the crossover is in the sub on these.  The sub has a high pass / full range switch for the pass thru connections.

Normally I run the main output into the sub first, then connect the outputs of the sub to the tops.

Do these tops have a crossover in them?

+1 on what Debbie said. Just run the signal from the subs to the tops. You have a very good sweepable HPF on each channel of the QU16. Because you have a good sweepable HPF, the benefit of aux fed subs would be minimal if any.

[Alan Chavis]

OK, thanks for the replies!  I'll skip the aux-fed for now and focus on dialing in all my HPF's.

[Mark Oakley]

Because you have a good sweepable HPF, the benefit of aux fed subs would be minimal if any.

I'm going to go against the grain here and totally disagree with this statement. Full-range systems with HPF's and Aux Subs are different things and achieve different results. In fact, I use HPF's and Aux Subs together on all 3 of my systems (powered mixer, wedding/corporate system, large 4-way trap rig).

Given the above mentioned gear I would:

1) Dedicate Aux 9 (post fade) to the subs.
2) Send the entire mix to the 712 tops, with a Hi-pass on the Main Mix Graphic EQ set around 90-
    100hz (125 if it's a loud show).
3) Dial in as much low end on Aux 9 as I wanted on low frequency instruments (kick, bass, floor tom, 
    DJ, maybe keys).
4) Set the HP Filters on the channels to whatever I needed them to be. On my iLive, I'll HPF vocals up
    to 160hz, guitar around 125Hz, etc.

For setting instrument levels, I'll first bring them up in the Mains to whatever level I need, then dial in as much sub as I need to add weight to the low frequency instruments. You can also set a LPF on Aux 9 to match the frequency of the HPF on the Mains.

-Mark

[Debbie Dunkley]

1) Dedicate Aux 9 (post fade) to the subs.
2) Send the entire mix to the 712 tops, with a Hi-pass on the Main Mix Parametric EQ set around 90-
    100hz (125 if it's a loud show).
3) Dial in as much low end on Aux 9 as I wanted on low frequency instruments (kick, bass, floor tom 
    (s), DJ, maybe keys).
4) Set the HP Filters on the channels to whatever I needed them to be. On my iLive, I'll HPF vocals up
    to 160hz, guitar around 125Hz, etc.

For setting instrument levels, I'll first bring them up in the Mains to whatever level I need, then dial in as much sub as I need to add weight to the low frequency instruments. You can also set a LPF on Aux 9 to match the frequency of the HPF on the Mains.

Or simply connect the subs to the tops and be done???

[Mark Oakley]

Or simply connect the subs to the tops and be done???

But then you'll loose any Aux control of the subs.

-Mark

[Debbie Dunkley]

But then you'll loose any Aux control of the subs.

-Mark

I know…I was just being facetious - forgive me.   
I am a bit of a stickler for keeping things simple if it works and my PRX rig has always sounded great doing things the 'conventional' way.   I do realize there is more controllability and flexibility with aux subs though.  Perhaps the OP could check things out both ways - your explanation of how to set up aux subs will be all he needs - and see which way he prefers to go.

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