4 point stereo loudspeaker placement

Hi all,

I'm curious about a particular loudspeaker configuration. I have an outdoor gig and the city (hosting the event) has strict SPL limitations. I was thinking about a creating an arc or line of ground stacks (4 full range stacks with subs) spread out to cover more of the crowd while keeping SPL within the limits.

I'd love to get your feedback regarding the advantages and disadvantages with this configuration. Here are some potential deployments.

Thanks!
 

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eriksquires

Member
2013-05-10 4:11 pm
Well, it's a little hard to pull off, but I like the Meyer's approach. Instead of circling your audience, stagger speakers in the audience, with time delay and EQ to fill in the sound properly. You can keep the peak SPL down, while maintaining a more even coverage across the audience. Also produces less peaks and nulls when you have competing signals from different speakers.

But I know very little about pro sound these days. :) Consult a real pro.

Best,

Erik
 
Erik, what you describe are delay lines, pretty common on larger setups these days.

Its not without its faults (if you want subs in the delay lines, the subs need to be directional, meaning more cabs and more DSP), but definitely works. The other problem is you're putting speakers in the audience, which is to be avoided unless you have plenty of crowd barrier and fencing IMO.


Subduction, can you tell us a bit more about the setup? - approximate areas, and what the "full-range stacks" look like?

Something I'd like to see implemented for PA use is the Double Bass Array, used by some HT enthusiasts. The idea is that you have two lots of subwoofers, one lot at each end of the intended coverage area. Delay the rear subs by the distance between the two sets, and then invert phase. The front subs produce a wave, the rear subs effectively vacuum it up again once it reaches the far end.
In-room, it kills room modes etc because the front subs effectively see an infinitely long room.

Outdoors, it'd stop LF propagating in that direction, though behind stage would get weird comb filtering.
If you've got enough subs and DSP, a cardiod sub at the front and then a delayed/inverted sub somewhere behind the audience should keep the city people very happy.

Of the two you've suggested, I'd go for the 2nd one. Getting speakers closer to people means you can turn them down a little.

Chris
 

SUBduction

Member
2014-10-11 3:13 pm
Thanks Chris and Eric,

Tops: 4x EV Eliminator II

Subs: 2x JBL JRX 4719x (loaded with 18XL1600)
2x Cubo Sub (BR, BP, Tapped Hybrid loaded with 18XL1600)

Venue: City park with no stage/barricades, very simple ground setup. Tops will sit about 1 meter off the ground on top the subs. Processing and amp channels are limited so I was going to link the outer tops through the inner tops and run at 2 Ohms. The DJ booth is located near the entrance of the park and people funnel in and out so audience size can range from 40 - 400 or more depending on the DJ.

I do have 2 available outs on my Driverack 260 so if I find another 2 amp channels I can have discrete delay control (Although I'm not sure how to apply delay to a 4 point setup)

The city is pretty ridiculous with the SPL limit (80 dB A weight @ the DJ booth!!!!). The monitor uses an SPL app on their phone (believe me, I've talked to them about calibrated SPL meters and such, the crowd will generate 80 db+ just by talking). I have a CM130 that I will use as a better SPL reference.

I have the suspicion that we are the scapegoat stage they like to keep around when the "Big stage" with a Meyer line array on the other side of the park plays way louder. "Ya it's those damn kids and their techno music making all the noise" ;) ;)
 
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A-weighted SPL measurements roll off the bass a lot. Use this to your advantage ;)

That said, with people like that running the show, I'd consider running a fairly small rig to make setup/tear down easier. Just a thought. I know it's not what you want to hear.

With no crowd barrier, I'd be careful with option 2. If you're happy for your cabs to get beer (or worse) on them, it's probably acoustically the best one.

Chris