Under stage sub-array

Tony "T" Tissot

Tony "T" Tissot

Freshman
Jan 31, 2011
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Northern California, United States
www.4dbsound.com
Under stage subs.



Anyone ever done a cardioid (or other) array <u>under</u> stage?



As they are no longer in conventional half or quarter space, would the predictions change radically?



Application would be (probably) 3 flush with the stage lip. Center reversed. Ported 1X18 or 2X18 - Not decided yet.



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Re: Under stage sub-array

Hey Tony,



It can change a lot. Part of the problem is the rear of the array is now firing into a ported chamber, which can affect the frequency response of the rear driver relative to the front, and vice versa. It's probably better than a conventional array since it will put less energy into that cavity. However, be aware that it will put nearly as much energy above it as a conventional array, where the stage is, so you may still have too much energy on stage where the performers are. Also, a three wide cardioid array puts its best cancellation in the horizontal plane, not the vertical.



Long story short, probably a cardioid ''type'' array is good, but I would not assume that the way you ''usually'' put it together will ''work'' as ''well''. If you have measurement software that will help a lot. Otherwise, be prepared to change your delay... I wouldn't even want to guess how much, and you may need some EQ as well.
 
Re: Under stage sub-array

I successfully did a cardioid array with 6 Nexo S2's under a hollow wood stage that was about 8'' taller than the subs laying on their sides. It works well down to about 38hz(measured), and then it goes to hell, but the LF on stage is a hell of a lot better than it was before. You can still feel the stage shake when you lay into the subs, but the audible LF is practically gone.



I had to play around with the delays and SMAART quite a bit to really get it working well.







Evan
 
Re: Under stage sub-array

Part of this excellent paper goes into some detail and computer modeling on the effect of the proximity of a stage in relation to a cardioid sub array:



http://www.aes.org/e-lib/browse.cfm?elib=15268



To summarize their findings on stage proximity effects:

''...it is evident that subwoofer placement directly underneath the stage can almost eliminate any advantages gained with cardioid polar patterns; the low-frequency SPL on the stage is virtually identical to that in the audience...Moving the subwoofers two meters forward so that they are not underneath the stage results in much lower SPL on stage while preserving the audience area response...''



 
Re: Under stage sub-array

So is there an array type that works well under a stage? It might be an interesting thing to write an article about, because often sight-lines and floor space issues can lead to less than optimal sub placement in this industry.
 
Re: Under stage sub-array

Are you talking about outdoors where the area to the rear is basically open, or an installed stage where the back and sides are inclosed?
 
Re: Under stage sub-array

Peter Etheredge wrote on Thu said:
Is that stage all wood I'm assuming?
Click to expand...



I had plans for a venus to build a large bass trap behind the subs..ended up not needing it but I now have another install with a lower stage and time will tell. If it sounds like I like out in front it is gonna be LOUD on the stage. We will see. Might want to do a ''regular'' setup and build a massive chamber for the subs at the front of the stag...if there is room. Hard to predict with a corner stage especially.



John
 
Re: Under stage sub-array

Peter Etheredge wrote on Thu said:
Is that stage all wood I'm assuming?
Click to expand...

Pretty much all wood.



I've put subs under stages before, and was never happy with the on-stage mess created.



Was hoping that there was an ''easy'' under-stage magic solution - ha!



The stage just becomes one big reflex box.



Conventional L/R looks to be the best bet. We want the floor space in front of the stage back. The picture doesn't show it, but we've been using some 18's center, on the floor..
 
Re: Under stage sub-array

What if you built a ''box'' under the stage to slide the subs into? Closed back, double walled with insullation all they way around.



I'm sure there will still be a certain amount of low end coming from the front, but would that help keep some of the lows from transfering through the stage floor?



 
Re: Under stage sub-array

Jamin Lynch wrote on Thu said:
What if you built a ''box'' under the stage to slide the subs into? Closed back, double walled with insullation all they way around.



I'm sure there will still be a certain amount of low end coming from the front, but would that help keep some of the lows from transfering through the stage floor?
Click to expand...



I believe some folks have built these using layers of cement board glued together with construction adhesive.

 
Re: Under stage sub-array

Jamin Lynch wrote on Thu said:
What if you built a ''box'' under the stage to slide the subs into? Closed back, double walled with insullation all they way around.



I'm sure there will still be a certain amount of low end coming from the front, but would that help keep some of the lows from transfering through the stage floor?
Click to expand...

That's one strategy, but I wouldn't get the cardioid sub-array behavior.
 
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