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Venue remodel: Sub bunkers?

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Ivan Beaver:

--- Quote from: dave briar on June 21, 2021, 04:35:18 PM ---Google says the density of drywall is 724kg/m3 whereas concrete is 2,400kg/m3 but no question Sheetrock would be easier to build and modify.  If it were me the Sheetrock option seems much more workable (I’ve never been enthralled with working concrete) but if the owner wants to indulge in some creative bunker construction that will work too.



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If you use sheetrock, it is advisable to use them double thick with alternating seams, glued and screwed.

That gets a lot closer to concrete density.

But hey, if he wants concrete, then just do that, but he must understand that he is pretty much stuck with the size for future sub choices.

Dave Garoutte:
You could do the MDF/sheetrock with a gap filled with sand.  The sand should be very absorbative due to the fact that it can move.

dave briar:

--- Quote from: Helge A Bentsen on June 22, 2021, 02:59:37 AM ---MDF forms the outer layers of the sandwich, so people are  performing on top of a solid surface. It's 1" MDF top/bottom with two layers of 3/4" drywall in-between, feels very solid to walk and perform on. Certainly  more  solid than most regular stage decks.  The sandwich floor is on top of 2x4" beams/legs not  connected to the sub bunkers. We used industrial carpet on top for less HF reflections from the floor and vacuum the  stage regularly.
I have no data on how effective this solution is, it was conceived as a cost effective solution using available materials and for ease of installation.
I've had several performers comment on how little sub there is up on stage after we did this compared to past experiences in the same room.

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Very interesting.  An alternative I have considered is adding a layer or two of 1/2” “cement-backer-board” (normally used behind ceramic tile in showers) between the two layers of HDF.  The cement board pencils out at ~1,200kg/m3 but drywall would no doubt be less expensive. Also planning on framing the stage on 12” centers — but that’s likely a discussion for a different thread.   Thanks for the details.

dave briar:

--- Quote from: Ivan Beaver on June 22, 2021, 08:19:13 AM ---…
But hey, if he wants concrete, then just do that, but he must understand that he is pretty much stuck with the size for future sub choices.

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True that for sure but worse case would be bringing the fork lift, lifting the bunker out (it will not be attached to the floor — except by gravity), carrying it to the dump trailer, and building new ones. Modifying a sandwich construction bunker would certainly be more feasible if we need it smaller but making it larger would likely be easier to just build over as well.  But wise council nonetheless. Thanks.

Ivan Beaver:

--- Quote from: dave briar on June 23, 2021, 10:14:56 AM ---True that for sure but worse case would be bringing the fork lift, lifting the bunker out (it will not be attached to the floor — except by gravity), carrying it to the dump trailer, and building new ones. Modifying a sandwich construction bunker would certainly be more feasible if we need it smaller but making it larger would likely be easier to just build over as well.  But wise council nonetheless. Thanks.

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Most people don't have the luxury of being able to bring a fork lift into the venue.

How would you get it out from under the stage?  Remember that the bunker needs to be airtight (or pretty close) in order to prevent leakage from getting under the stage.  That usually means attached to the stage itself, with a good seal against the floor, and the front of the stage. 

Were you also planning on removing the stage and front in order to get the bunker out?

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