Bass/subwoofer beam steering using acoustics/buildings/surfaces/baffles

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I have been doing a few shows in an outdoor venue and they have had lots of noise complaints from the surrounding residents. They are thinking they may pull the pin on having any future shows there anymore.

I have been trying to find out if it is possible to use acoustics/buildings and surfaces to steer the bass from conventional subwoofers out into the bay and minimize the coverage to the sides to our neighbors.

The venue is outdoors and one side faces out over a cliff and into an empty bay/river system. The potential plan is to use the existing large building (with modification) to create an acoustic shield around the stage so that it directs the low-frequency sound energy to hopefully a 90deg pattern into the crowd, then out into the bay.

I was considering cardioid subwoofers or arrays but I'm not sure how well they fare when backed up against a big building and a better solution may be the building acoustics itself with concrete baffles or something.

If I can organize to create some concrete baffles to direct the reflected subwoofer energy how big would they need to be to reduce the effect of having the low energy sound waves bend around the edges? Or does this only work if all sides are closed off by acoustic barriers right down to the bay edge?

The mid/top frequency range should not be a problem if we move to something like Danley speakers with great pattern control. Its the low frequencies that I am not so sure about...

If anyone has any experience or knowledge can you help point me in the right direction, is this idea possible or am I better off just going cardioid or giving up?
 
I have been trying to find out if it is possible to use acoustics/buildings and surfaces to steer the bass from conventional subwoofers out into the bay and minimize the coverage to the sides to our neighbors.

Yes.. but you won't do it cost effectively with room treatments you want to use a cardioid subwoofer array.
The End Fire Cardioid Subwoofer Array Made Visible - ProSoundWeb
http://www.fohonline.com/current-issue/74-tech-feature/8711-subwoofer-arrays-in-the-real-world.html
 
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Sorry for the delay, things have been hectic and I also replied earlier but it did not post for some reason.

Here is a maps view with a bit of info. I roughly drew in the stage. from looking at things the far side guest rooms won't be as much of an issue so less directionality may be ok, its more just the rear of the stage that presents the biggest problem.

Mangrove aireial drawing.jpg - Google Drive

I am still keen on the idea of concrete FOH barn doors but I don't have much to back up this idea at the moment. I can't find much info on the web about this sort of thing.

My hesitation with cardioid arrays and subs is that it doesn't seem ideal for the broad range of low frequency I need (40-200hz evenly) and it does not seem to be that cost effective. this will be a permanent setup and system so building for directionality in mind may be the way to go.

Here is looking out from the stage area
20170719_135559.jpg - Google Drive

and looking into the stage area
20170719_135505.jpg - Google Drive

and the whole folder of images
Mangrove Hotel - Google Drive
 
My town is on the water has a large bike festival with some pretty serious SPL and had similar issues. They tried firing toward the water and it actually helped quite a bit. I doubt there cardoid arrays were employed. Worth a try at least. That said, noise complaints are not always about noise per se. It could be hours of operation and the event could be running later than residents want. Maybe move it up? I would take a look at local code about noise and find out your limits. Also, that venue seems rather small and I am not sure there is truly a need concert SPL. Honestly, that gig looks like solo acoustic and not dance club at all. If you are running stacks of 18's then I think that is overkill (my middle name). Alternately, providing some incentives to the offended can help. Gift cards/free entry/or cold hard cash. If you are trying to run a dance club in the middle of a retirement community there might be little you can do. How far away are the offended?

WRT barriers. In my area the DOT has added these along most highways and I suspect they would help. https://stonetreefence.com/sound-wall-noise-barriers.html In the end, you want MASS to absorb LF. Pick up Everest's Acoustics and learn. I would have to research but I think the simplest most cost effective way would be to build up the earth to a suitable height to create a barrier. Get the word out and I bet you could get it for free then the only cost would be to make it pretty. I would send a PM to Art Welter. No doubt he has some experience with this sort of thing.
 
Thanks, That's a good article and has helped me to make some plans.

I am an overkill man myself however they sound system will be completely controlled by the venue and therefore various rules and cutoffs will be in place and likely to be more extreme than any local codes. They would not require concert grade spl but they do have bands in on a regular basis. The small stage and FOH system I plan to be multipurpose and used for private functions and events from small to medium in size. The system can be connected to the venues normal speaker array throughout the outdoor area to provide additional coverage at low volumes or be independent.

The two biggest considerations to me seem to be subwoofer or low-frequency control and also stage spill from bands who want gobs of fold back.

I would love to go center/mono subs but building a barrier in the center of the stage is a no go for obvious reasons although I have not ruled out a single sub setup on one side it is a little awkward but may be the easiest option.

The best idea I have at the moment is to use concrete wall barriers for FOH subs and place the subs either against the wall or even built into it (purpose built hole). Then the stage can have a back concrete wall with treatment on the surface for bands. All the walls would be back filled with earth possibly even to the full height and be covered in plants which would poke over the top too.

The thing is that this kind of a setup is using a lot of different acoustic principals at the same time. The barrier walls are reflecting and absorbing but due to proximity would simulate wall/corner loading of the subs (like indoors). Then there is also diffraction which is even more important to determine the size of the barrier and its effectiveness.

If the walls can be built big enough to overcome the diffraction problem as well as being much more of a reflection surface than absorber would mean that less spl is required from the subs to achieve the same audience spl levels too. That's why designing this sub barrier/enclosure well to increase SPL and directivity is a great idea.

For reference, my current overkill idea of FOH would be two danley os80's and no more than two double 15"/18" subs or equivalent usable to 45-50hz. I would probably impose some serious limits on the output of this system in the dsp since I think for most events this would be overkill. Also, the staff would turn it down after 9:30 and shut it down probably by 11.

I am liking the idea of a single side mono grouped subs much more as it requires a lot less space and barriers which will be a limitation.
 
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Love Danley and did not know they had outdoor stuff but those appear to be a bit wide for you even though the 80 is narrowest of the line. You must have much larger budget than I suspect... I have a Keystone myself and it is a serious box and one is basically a dual 18. First thing I'd do is build a pair with those extensions. Directivity at 180deg is -7db @ 60hz and -14db @ 125hz.
 
Well now thats some neat info. I have a pair of th18s too.

Now I am thinking of V plating a pair of th18, also continuing the V as horn extension an extra few meters each side. Then possibly burry the whole thing a bit and use the top as the stage. The mouth would be as big as the stage almost.

Could be pretty compact and require a lot less concrete and earth works...
 
Not sure on the budget at all so far but I have a pair of sm80 and the directivity is pretty crazy untill 200hz. I can offset the cost by using an Inuke dsp amp and justify the weatherised outdoor version and directivety. FYI the os80 is significantly cheaper than the sm80 too.
 
Sounds like you have things to try. Sub/stage sounds is fine for DJ but live kick drum mic will probably be a feedback issue.

I got this now... :D I would definitely suggest a semi-permanent stage with subs under. Line interior of sub area with 2 layers of rock board or green board. Old local bar had subs under wood stage. Fire inspector says not code and must line inside with drywall. To our surprise it drastically reduced stage volume/you could hardly hear subs at all... Best money they ever spent. Make weather cover for face of stage during off hours. Then if you can, design it with a roof for foul weather gigs and that ends the monitor spill... Throw up some par cans inside.
 
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