Yeah, I’ve got the system there already, although I have a new turntable I need to assemble. And missing a shelf from my rack.
I’ll post pictures after I get it looking reasonable.
Acoustically Treating a Bomb Shelter
Seriously. My house came with a 1960s era bomb shelter. It's a total of 2,200 square feet of Cold War Era awesomeness, basically divided into two 51X21 long rectangular rooms.
It's under a pool and pool house, easily 15 feet down. Hard concrete walls. Huge metal out swing doors that could keep out Bob Dylan looking for a string bean.
We turned one big room into a giant pantry, wine cellar, and storage room.
The other I softened with hardwood floors, sheet rock (with foam insulation) on walls and ceiling, in that it could make an excellent apartment, being 1000 sf by itself, not counting the kitchen and bath. And has two entrances, one at each end. Very airy with good ventilation (and expensive filters).
It's this (now) 50 X 20 room iswhere my listening area is. Ceilings are 14 foot sloping down (the short way on the rectangle) to 12 feet.
I've divided it into three areas of roughly equal area. One end has a power rack and tons of free weights and whatnot. On top of the hardwood is a protective layer, hardwood, and then rubber horse stall mats. Kitchen and bath beyond that.
The other end is an emergency bedroom, with flip down Murphy beds, etc. Area rug where the wife does yoga. At its end are double metal doors, then stairs, then another metal door.
The middle third is my listening area. Speakers and subs on the higher-ceiling side, although I could flip it. Set up in the classic 60 degree triangle with a leather couch facing the speakers. Chairs to the side, and a table I use as a desk behind the couch. Area rug. Decor: think Andy Warhol meets Austin Powers.
My thought is I don't get a lot of reflection from either the right or left side, due to the width of the room, and the stuff in each room. I suspect I mainly get reverb off the back wall. And perhaps the ceiling, although it is sloped up to the speakers.
I'm thinking all I need is some absorption on the back wall, immediately behind the couch/table (so facing the speakers), as I sit closer to the back wall than the speakers. Perhaps something on the ceiling about 2/3 of the way across the room.
Thoughts? I'd like to be informed a tad before I get involved with GIK or one of those groups.
Showing 15 responses by davetheoilguy
Just to update: talked with a number of audio room advisors who offer consulting services. Most are just pushing their particular products. One, in particular, who I'll call "Dennis" was particularly abhorrent example of the acoustic field. He may or may not know his stuff (probably is extremely smart), but he was talking fast, pushing hard, and coming to conclusions to sell his product clearly based on simple computer room analysis and not taking into account the odd nature of the walls and actual measurements. Specifically, because we are deep underground, the "drywall" is not drywall, but a product designed to allow water to pass through, made with little beads and glued together (in the unlikely event of a water event). Underneath that is six inches of a dense expanding foam. Basically, the top sheet is very close to being acoustically transparent. Not sure what is going on, but from multiple measurements with several different tools now, the walls do not really reflect much (nor produce their own sound) but are mildly absorbent of very low frequency sounds. Long way of saying, computer room analysis is a great tool, but no substitute for direct measurements. With that in mind, after talking with the rare consultant who actually listened to measurements, I've decided to go with about 20% bass absorption and 20% dispersion. Mounted 4" combined bass traps/dispersion immediately behind the speakers/subs (about 1.5 inches from the wall). (The gap increases the depth of sound absorbed, while decreasing the effect on higher frequencies.) This made an immediate improvement. Going to do about 108 sf of combine bass trap and dispersion on the back wall, and a fair bit on the ceiling, depending on results of back wall. Nothing but a simple thin carpet on the floor. My problems are low frequencies, and it would take building a pit to have something thick enough. (A carpet with pad will just absorb high/mid frequencies.) If I need more, I'll double up on the ceiling. The only other covering I'm doing is on two metal blast doors (on the far right) that have a huge tendency to vibrate with bass and give a solid echo. Not a fan of acoustic curtains, since like carpet, they mainly just absorb higher frequencies. I've decided to use three layers of curtains -- one a heavy acoustic curtain, one that is pretty and acoustically transparent ---- AND HIDDEN IN THE MIDDLE GODAWFUL BEADS AND COINS. Why the faux "gypsy" (er, Romani? If I was Romani, I wouldn't claim it. It's from Spencers.) -looking garbage? Dispersion. I bought twice as much as needed, and they will hang all "bunched up" and hard, facing random directions, thereby taming down that 10'x7' metal reflector of a blast door. Even better would be to have hanging wood slats, but I couldn't seem to find any. Will see what happens. Cost total of the awful beads and "coins" = $39. If that doesn't work, I have enough space in the door frame (also a giant slab of steel) to mount 6" base traps directly to the doors. |
I do have REW software, a mic, and a mic stand, but in process of figuring out the software. Yes, the space is heated and cooled, but really maintains a pretty constant temperature without help at 67F, very dry. The ventilation system can be passive (assuming lack of electricity or desire not to have it on) or active. The venting tubes and machinery are all on the other side of the wall, except a large exposed suspended tube that is on the far left that may or may not have resonance issues It's called a "high volume low pressure" system and is quite literally designed to filter out fallout. As relevant here, it's completely silent. |
Yes, it actually has a lot of dedicated power outlets, already. With a lightning arrestor, whole facility surge protector (not the same as a lightning arrestor), and filter. It was originally designed to protect against EMP. I've replaced the elements due to age, but the amount of copper used was amazing, as is the grounding. I run my whole rig off a dedicated 20 amp circuit, going through a commercial Furman. Wifi was futile, outside of one room at a time. I had to run ethernet cable. |
Plus, it's not like loud music would bother anyone. In seriousness, it's a just a very giant empty room. Not dark or damp or whatever. Excepting the fact you walk down a flight of stairs and through a mud room (er, "decontamination room" made to look like a mud room), you'd never know you're in a bomb shelter. Zero noise from anything. And while we haven't had to shelter from bombs, during a couple of tornado warnings, we have made our way down. |
The underlying walls and ceiling are concrete, but I put in a vapor barrier and 1 inch insulation, then 2x4 (2x10s in the ceiling to space for steel I beams) and then 5/8 drywall on top, The void is expandable foam insulation. Looks like firm yellow shaving cream. All of that is not structural. Just insulating and gave me a place to run conduit and make it look like a normal room. The main issues I have a acoustically are: 1. It’s a big room. Right at 1000 sf. 2. It’s almost a hallway, being 50 feet long and 20 deep. And I’m setting up across the short side of the rectangle. So reflections from L and R are quite distant. 3. ceiling has a fair slant to it from 14 to 12 feet, which presumably reflects sound back to the speakers, but probably somewhere between the speakers and couch. 4. I’ve got it set up where I listen closer to back wall, which is why I suspect that is my point of unwanted reverb.
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We have a home theater already in the house proper. It’s very typical McMansion stuff put in by the owner of the home between us and the survivalist builder, straight out of the mid-2000s, albeit with a new QLED. I suspect they walked into Magnolia and just picked the most expensive stuff they sold. It’s certainly nice enough in a cheesy way. Made watching Into the Spiderverse awesome. But that is for the kids and currently has a PS5 strewn across the carpet. This is for me. |
It's 2.5 feet of hard concrete and steel under ~15 feet of dirt under a swimming pool or deck. Pretty sure it's a giant Faraday cage, too. Cell phones go completely dead, something I very much enjoy. So, I think we're OK with radiation. ;-) On the serious point, my playing with Dirac Live on the Arcam/laptop and a brief online consultation told me the same thing. Nothing is needed on the left or right side, due to the length of the room. All that is needed is either diffusion or absorbtion on the back wall, immediately behind the listening area, together with a bit directly above the sofa on the slanted ceiling. Also pulling out the speakers about two feet from the forward wall (which I had already done). I have a large (5' x 5') oil painting on the back wall. I'll see if acoustic foam hidden underneath in the void works. The slanted ceiling is apparently ideal and a bit of a mini-ampitheater.
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@kennyc I can tell if you are joking or just utterly failed to read the thread. |
1. Am Israel Chi! Go do whatever is necessary, please! Ignore the media. 2. For clarity, I live in West Texas. This house was built by an extremely wealthy oil man back in the 1960s during the height of the Cold War. Very rural. If I ever have to shelter from bombs it’s because China Russia and the USA have decided to have a massive nuclear exchange. All in, the shelter is as large as most people’s houses. 3. Yes, we have plenty of food. And about 2000 bottles of French, Californian, and even Israeli wine. All set for the apocalypse. Also a rather large library. 4. We are fortunate enough here to not be preparing for said apocalypse, but rather finding something useful to do with a massive room with wonderful filtered electricity and completely silent, if oddly shaped.
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It’s the SVS PB16 ultras. It’s a big room and they move a lot of air and just add the required depth to the bottom end. Very noticeable without overpowering. Takes some of the burden off the monoblocks. Set crossover (coming out of the preamp) at 50ish and slope at 24 by ear, which, turns out is exactly what SVS recommends for the 800. |
Thanks for the advice. As noted, the side walls are too far away to be of concern, but I do have a pretty pronounced standing wave. I’ve bought multiple 4 inch thick panels for the back wall and behind the speakers/subs.. Also a bit just behind the turntable (dead center). Moving the subs inside the primary speakers also helped immediately, as did widening the distance between the primary speakers from the classic 60/60/60 triangle by about 4 feet. The Bowers 800s have plenty of “umph” with the big subs and Classe amps to handle being offset. Really helped with separation. Because of the canted ceiling, I’ve got 3 hanging baffles (pretty thick) staggered behind the listening position that I’m going to hang this week. The back panels placed in the center back also incorporate some dispersion elements.
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Well, according to the two detectors, no radon! Re: the poster freaked out about this being a cave. My wife is, too. The second owner added a Huvco fibreoptic daylighting system to this, but didn't finish. He put in the collectors and bought fake windows, but didn't finish the system. I'm going to run the cables down through the internal wall and stick in the "windows" to decrease the cave effect. |