Two Channel Listening Room in a Bomb Shelter

[Davetheoilguy]

Hey all. My name is Dave, and I'm an alco . . . an audiophile.

I finally have a house suitable for a proper listening room, albeit one that doesn't quite fit in the standard dimensions or building materials, which is what brought me here.

It's literally a former bunk room in a bomb shelter. The room is precisely 1000sf of 1960s Cold War, Cuban Missile Crisis, awesomeness, 15 feet below a pool and pool house behind my house. All in, the facility is about 2500sf. About a quarter is now a giant storage room, another quarter a wine cellar, and then this room is primarily just a listening room, albeit one that is 50 foot wide and 20 foot deep with solid steel double doors on each end.

Hardened concrete walls, that (before I decided to make it a listening room) are now framed and spray foam insulated. The inside walls are a drywall-looking substance designed to get wet and drain if water gets behind it. It's basically a giant box and you'd never know you were underground, but for the eerie silence.

For good and for bad, the walls don't seem to resonate like drywall. It's like little plastic beads held together by fibers and some mysterious substance, almost like acoustically transparent rockwall, but not crumbly. My measurements, so far, have shown it not behaving according to most of the simplistic models that assume drywall. (This could be because of the foam that filled the void. Or maybe the slanted ceiling. Or maybe the giant I-beams and super-hard concrete behind the false wall. Regardless, here we are.)

To complicate things, for various logistical reasons (literal double thick steel blast doors at each end) I had to set the listening area across the short (20 foot) distance. Ceiling is high and has a fair slant to it, starting at 120 inches, then dropping a foot to the back wall at 108. So, yes, the ceiling is slanted the wrong way from ideal.

Anyway, complicated space. I'm listening and taking measurements, changing or adding one thing, then taking measurements and so on.

And, most importantly, throwing myself on the mercy, intelligence, and experience of the veterans of this forum.

 

[Todd Anderson]

Hey Dave -

Thanks so much for joining the community!

WOW wow WOW! That room reads like something out of a mystery novel! Your description makes it come alive... I wish I could see it. Hopefully you'll post some pictures of all of it... from the entry way/steps, to blast doors, to the room. If anything, you have one of the most unique hangouts on the forum!

If I'm reading it correctly, you have constructed a room within the room?

 

[Davetheoilguy]

Kind of a room within a room. I put in framing (2X4s on the walls and 2x12 on the ceiling -- due to thickness of I-beams) on the concrete, ran electric wires, sprayed in foam, and then put on this sheetrock-like material before the foam expanded.

The really cool part are things like the lightning arrestor, massive surge protectors and multi-fuel generators. And a water well -- inside. All designed to stop/survive EMP. It's basically a giant Faraday cage.

You walk 10 steps down and your cell phone stops.

 

[Sonnie]

Definitely has some cool factor to it (probably a pun)... perhaps a good idea.

 

[Davetheoilguy]

Yeah, I'm not a survivalist at all; we just liked the house. This ended up as a bonus.

Noise floor, BTW, is basically zero. So if I can figure out all the amazingly nasty, super low, standing waves and whatnot, I'll be in good shape.

 

[Todd Anderson]

I hope you call it the audio bunker!

 

[Sonnie]

I want one!

 

[Todd Anderson]

How is it heated and cooled?

 

[Sonnie]

It wouldn't need cooling... probably 60 degrees year-round. Not sure how it would be heated. Our storm shelter underneath our house stays very comfortable year-round. A bunker that deep though, probably a bit cooler and would need some sort of heating. Curious what you have as well.

 

[NBPK402]

What a score!

 

[Davetheoilguy]

This is the desert so it’s dry. I prepared for water because it’s under the pool.

Re: temperature it maintains about 62 by itself but will heat up quickly with people or amps but it has both an oil heating system (using waste heat from the generator if on or electric coils if on the grid). And what is called a “high volume low pressure” air system (which would trap fallout). It can run passively with wind but obviously works more consistently with the grid.

Because the air is not particularly forced along it is quiet when in operation, which is nice.

But one of the audio issues (not yet discussed) is the giant round steel duct (haven’t measure but probably an 18 inch radius) that runs under the ceiling and abruptly stops in the middle of the room. (It can’t go inside because metal I-beams are in the way.)

Pictures will come, but they are disappointing. It looks like a giant light beige room at the moment. I do have some of the original furniture, though, which I am fairly certain were cast offs from Mad Men and Austin Powers production sets. Maybe BeWitched.

 

[Todd Anderson]

This is all so fantastically cool. Love it!

 

[firedog]

I'd add some kind of acoustic panels in front of or actually on the steel doors and reorient the room along the long walls.
I'd also think about adding some panels elsewhere - at least corner bass traps.
These can dramtically improve your results, especially in that kind of room.

Some manufacturers of panels (GIK and others) will give you free advice about how to deploy panels - at a price level that you set.

After that, measure and setup a convolution file to further improve the results.

 

[ddude003]

I would consider creating a false wall in the front and back making the enclosing space a more reasonable acoustic space... Yes, there can be doors in them... There are many formulas and rules of thumb as to what the "golden" size(s) are suppose to be... Google is your frenemy... Use https://amcoustics.com/tools/amroc?l=35&w=20&h=9.5&ft=true&r60=0.6 for a glimpse at what room modes would look like... The false forward and rearward walls can be treated with bass and wide band absorbers as well as the left and right walls, floor and ceiling... This Argen web site has a lot of great information http://arqen.com/bass-traps-101/placement-guide/ and you may find a copy of the Master Handbook of Acoustics by F. Alton Everest and Ken C. Pohlmann is a handy reference...

 

[Davetheoilguy]

Love the ideas about partitioning the room, but they are a no-go due to logistics of getting materials down to the space and no desire to try to figure out mechanics of ventilation. Getting 21 foot long 2x12s for the ceiling joists almost caused me to murder someone.

Sticking with tried and true strategies of acoustic absorption and dispersion. And having two giant subs, 400W Classe monoblocks, and B&W 800s for speakers to fill the space.

 

[steve138]

Hey all. My name is Dave, and I'm an alco . . . an audiophile.

I finally have a house suitable for a proper listening room, albeit one that doesn't quite fit in the standard dimensions or building materials, which is what brought me here.

It's literally a former bunk room in a bomb shelter. The room is precisely 1000sf of 1960s Cold War, Cuban Missile Crisis, awesomeness, 15 feet below a pool and pool house behind my house. All in, the facility is about 2500sf. About a quarter is now a giant storage room, another quarter a wine cellar, and then this room is primarily just a listening room, albeit one that is 50 foot wide and 20 foot deep with solid steel double doors on each end.

Hardened concrete walls, that (before I decided to make it a listening room) are now framed and spray foam insulated. The inside walls are a drywall-looking substance designed to get wet and drain if water gets behind it. It's basically a giant box and you'd never know you were underground, but for the eerie silence.

For good and for bad, the walls don't seem to resonate like drywall. It's like little plastic beads held together by fibers and some mysterious substance, almost like acoustically transparent rockwall, but not crumbly. My measurements, so far, have shown it not behaving according to most of the simplistic models that assume drywall. (This could be because of the foam that filled the void. Or maybe the slanted ceiling. Or maybe the giant I-beams and super-hard concrete behind the false wall. Regardless, here we are.)

To complicate things, for various logistical reasons (literal double thick steel blast doors at each end) I had to set the listening area across the short (20 foot) distance. Ceiling is high and has a fair slant to it, starting at 120 inches, then dropping a foot to the back wall at 108. So, yes, the ceiling is slanted the wrong way from ideal.

Anyway, complicated space. I'm listening and taking measurements, changing or adding one thing, then taking measurements and so on.

And, most importantly, throwing myself on the mercy, intelligence, and experience of the veterans of this forum.

I would recommend watching all the webinars by Anthony Grimani on Audioholics and AVProEdge about room acoustics and treatments. I’ll be treating my rather smaller Home cinema room according to those principles. I would definitely make your space into a Home Theater and listening room. With a front partition wall with front LCR speakers firing through an acoustically transparent projection screen and all the ATMOS. Surround and height speakers and subs behind stretch fabric. Best is to have four subs in the four corners or even better apparently is four ceiling mounted 25% in from each corner. Good luck and do keep us posted of course a good surround processor will be needed too. I got the ANTHEM AVM-90.