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post #1 of 12 Old 09-20-2017, 10:11 AM - Thread Starter
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Question New Construction / Dedicated HT Build... some questions

Greetings!
My wife and I are building what is hopefully our forever home now that the kids have left the nest... well most of them. The area under the garage is being utilized as a dedicated home theater and storage area... so all four walls are concrete as is the ceiling. It currently sounds like a crypt in there, but I don't think I'm going to have to worry about containing the sound too awfully much.

My main concern is taming the echo in the room. It will be furred out with 2x4s all around, with either a suspended or finished ceiling, haven't decided which. I'm just not certain how to finish the walls, and hopefully you all can give me some direction. Will traditional drywall backed by fiberglass batting and covered in traditional sound absorbing panels be sufficient or will I need to use something else?

I'll be asking lots more questions about wiring and such, but right now the echo removal is at the top of my list

Thanks in advance for any assistance!
Eric
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post #2 of 12 Old 09-20-2017, 11:03 AM
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Concrete has lots of mass and will help very significantly with sound isolation. The heavier something is, the harder it is to vibrate, and therefore transmit sound. However, do take note that once solid materials are vibrated, they actually conduct sound better than air. Think about the old trick of putting your ear on railroad tracks to hear the train coming long before you can hear it through the air. The trick is to add isolation, so that you don't vibrate the walls and ceiling in the first place. Since you will be building walls with 2x4s inside the concrete shell, go the extra step to isolate them from the structure with iB3 clips or similar, so that they don't touch the rest of the structure. The ceiling should be suspended from the structure with clips and channel, or you can build it with floating joists that sit on top of the walls and don't touch the concrete structure above.

Read more about the four elements of soundproofing here. http://www.soundproofingcompany.com/...soundproofing/

Keep in mind that a despite being referred to as "acoustical ceilings", traditional suspended ceilings have almost no acoustical properties. Sound will literally go right through them like they are not there. They may help somewhat with high frequency reflections, but that's about it. You are much better off with a finished drywall ceiling.

A concrete wall will have terrible acoustical properties, as will a room with just a drywall shell. (Just try listening to any of the drywall finishing videos on YouTube, they sound terrible!) Carpet and furniture will help a lot. You can add additional room treatments beyond that. This is an excellent source for more information.
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post #3 of 12 Old 09-21-2017, 07:36 AM - Thread Starter
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Thanks for the response Dave! I browsed the info at the link you gave and found it helpful. It seems I need to decouple the framing from my poured concrete walls, but I'm not sure the best way to accomplish this. Given that the concrete walls are 6"+ thick, do you there will be a vibration concern if I attach the framing directly to the concrete and then decouple the sheetrock from the framing? If so, what should I use to decouple the framing from the concrete?


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post #4 of 12 Old 09-21-2017, 08:01 AM
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I would build the wall 1 and 3/4" shorter than the height. Then stand it up. Then put another 2x4,(1 1/2") under it. Now u have a quarter inch gap to the floor joists above. Shim it and nail there. Now u have no holes in your concrete. That being said u can use some scrap blocks to keep it off the wall. That way no one can push the wall in. And obviously no one can pull it out since u won't be back there. That being said this only works for walls around foundation/perimeter
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post #5 of 12 Old 09-21-2017, 11:57 AM - Thread Starter
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Thanks AJ... so you are suggesting that the walls be stood up leaving a gap between them and the concrete foundation walls? In this case, all four walls of the room are foundation wall, and the ceiling is concrete slabs (literally a bunker as another member referred to theirs), so I would essentially build a room inside a room and then use some decoupling clip to mount the ceiling joists to the walls?
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post #6 of 12 Old 09-21-2017, 12:46 PM
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Everyone on here has a way of doing things, but that's how I would. I never like poking holes in my concrete slab. Period. That's exactly how I'd do it. My dad did it that way 27 years ago and the walls are perfect. He made em two foot off so he could walk around behind the walls if need be. As for the most acoustically best situation, that you would have to ask an expert because that definitely is not my cup of tea.
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post #7 of 12 Old 09-21-2017, 12:52 PM
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And you don't need any fancy clips. Literally a shim at top of wall and against your floor joists above will create enough pressure to keep wall from moving. Throw a nail or two up there. That's it. Wall won't move towards foundation cause you will have scrap 2x4s along bottom, and nailed at top. Wall can't come in cause no one is inside pushing that way. Also, if you ever had too, for some unforeseen emergency(say something wrong with a drain tile, or a leak in the wall, but let's pray not) you pop the nails put up top, and can literally move the wall. If it was nailed into the concrete, it would be much much harder.
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post #8 of 12 Old 09-23-2017, 05:42 AM - Thread Starter
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Quote:
Originally Posted by AppleJack123 View Post
And you don't need any fancy clips. Literally a shim at top of wall and against your floor joists above will create enough pressure to keep wall from moving. Throw a nail or two up there. That's it. Wall won't move towards foundation cause you will have scrap 2x4s along bottom, and nailed at top. Wall can't come in cause no one is inside pushing that way. Also, if you ever had too, for some unforeseen emergency(say something wrong with a drain tile, or a leak in the wall, but let's pray not) you pop the nails put up top, and can literally move the wall. If it was nailed into the concrete, it would be much much harder.
There's the rub, there are no joists at the top... the current ceiling is a suspended concrete garage floor at a height of 11', so I'll also have to install ceiling joists as well. In thinking about it, would installing the joists using these (http://www.soundproofingcompany.com/.../ib-3-bracket/) as decouplers work, or am I thinking about this all wrong?
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post #9 of 12 Old 09-23-2017, 06:37 AM
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Perfect clean slate. I wouldn't use any clips for the ceiling joists.
Run them on top of your walls. Make sure to do a double top plate because your walls will be bearing now. You could use clips to secure your walls to the concrete walls.
Make sure you leave a 1 inch gap on all framing from concrete.

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post #10 of 12 Old 09-23-2017, 06:49 AM
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What are the dimensions of the room?

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post #11 of 12 Old 09-23-2017, 10:22 AM - Thread Starter
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Quote:
Originally Posted by Medi0gre View Post
What are the dimensions of the room?
So the dimensions are 16' wide x 25.6' long (prior to framing)... and I'd like to keep as much of the width as possible. I've linked to my cursory floor plan for the room, all comments are welcome...

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post #12 of 12 Old 09-23-2017, 01:19 PM
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With an 11' ceiling you could literally build a room within a room with the floor being the only thing common to both.
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