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Author Topic: Subs Under Stage  (Read 2593 times)

A.J. McGlynn

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Subs Under Stage
« on: May 06, 2009, 03:14:14 pm »

So I have been wondering this for a while but never got around to asking about it.

My system was designed before I came on staff so I wasn't able to get to the bottom of this when it happened. I have 2 EAW Sb1000's under my stage. One on each side. The are built in to boxes under the stage. I have pictures attached to know what I am talking about. I have never seen this done before and am wondering if this would cause problems. I have never been happy with the lows in the room but part of it is room design as well. Let me know what you think.

index.php/fa/392/0/
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A.J. McGlynn, Technical Director
Grace Church
Erie, PA

A.J. McGlynn

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Re: Subs Under Stage
« Reply #1 on: May 06, 2009, 03:16:01 pm »

This is a pic from the front.

index.php/fa/393/0/
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A.J. McGlynn, Technical Director
Grace Church
Erie, PA

Matthias Heitzer

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Re: Subs Under Stage
« Reply #2 on: May 06, 2009, 04:07:50 pm »

Subs under the plattform have the pontantial to shake the whole stage. Rumbling and ugly resonances can be the result.
It can even cause feedback, if the vibrations are conveyed to the microphones.

Time alignement is another issue, but should not be such a big problem with modern processors.

Can you take one out and then A/B- test the your system?
If you hear no difference, everything is fine.
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I'm from Germany,so please excuse my bad english.

Robert Sims

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Re: Subs Under Stage
« Reply #3 on: May 06, 2009, 04:11:51 pm »

Looks ok to me, you'll pick up a little gain by doing it that way and keep some of the energy from spreading underneath the stage. Hope everything is screwed tight. I'd be more worried that the subs are on each side rather than in the center as that will create some lobe'ing issues depending on how far apart they are. What is it about the lows you don't like? There may be something else going on.
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Robert Sims
Technical Director/Engineer
Hope Baptist Church
Systems Engineer
CES Las Vegas

A.J. McGlynn

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Re: Subs Under Stage
« Reply #4 on: May 06, 2009, 04:37:00 pm »

I wish I could get them out to A/B but I dont think it would be very easy. They are in there pretty good. I also wish They were in the center. I really wish they were flown but thats a whole other debate. Vibrations haven't really been a problem that I know of.

The subs sound muddy and don't have a lot of punch. I know that is vague but thats all I got.

It's also weird because there is hardly any sub energy under the stage. I am able to mic a guitar cab under there with no problems. I would expect it to be way worse than it is.
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A.J. McGlynn, Technical Director
Grace Church
Erie, PA

Robert Sims

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Re: Subs Under Stage
« Reply #5 on: May 06, 2009, 06:29:29 pm »

A.J.
Hey remember that sound is movement of air. If those boxes are air tight, most of the energy is being directed forward. Vibration through the wood is where most energy under the stage would come from. Make sure you not only cross over the low to mids, but also take out energy on the low (20hz) side as well. The manufacture is recommending a 12db butterworth HP at 25hz. The speaker is rated to 28hz at (I assume) 3db down. Not sure what kind of music you have going on, but I'm pretty sure you don't need it that low.

I would move that up a little and see how it responds. Of course I assume that you are aligned to your mains. You have very large 18" drivers (2 per) that are hard to get moving and once they are moving are hard to stop because of all the mass. Anything you can do to minimize the travel might help them tighten up. The best way I know how to fix that is to limit the low end of the lows.

If you are not using Aux fed subs you might try that. Anything you can do to eliminate all material other than lows you want to hear will help.

If you have Smaart or something similar, an impulse measurement might reveal if there are room issues involved.

Is it muddy on everything or the peaks like a kick drum? I call it muddy when the bass player moves a note one step and I can't tell the different or hear the transition.  Smile  

Just curious, you ever have problems with video while the subs are playing??
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Robert Sims
Technical Director/Engineer
Hope Baptist Church
Systems Engineer
CES Las Vegas

Jeff Ekstrand

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Re: Subs Under Stage
« Reply #6 on: May 06, 2009, 08:49:12 pm »

I know plenty of great venues with subs under the stage. It is not an automatic recipe for disaster. On the other hand, even designs that have great reputations, when implemented improperly, can sound terrible.

The lack of punch could have a little to do with the design, or it could be system tuning. I know one church who had a similar implementation, and the system was tuned so that the subs just filled-in a little low end because they didn't want to blow-away the congregation that thought subwoofers were overkill. In fact, most members didn't even know the subs were there... and I could hardly tell most of the time. A bit of a waste of Meyer subs, if you ask me.
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Jeff Ekstrand

Technical Director, North Shore Campus
Willow Creek Community Church
Northfield, IL
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