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post #1 of 18 Old 06-13-2012, 07:41 PM - Thread Starter
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The underlying question behind the question is "Do I need/should I build a room within a room"?

The reason for the question is simple....money.

The walls will be treated with acoustic material/fabric. There will be double drywall with green glue.

I'll try to ask several questions that are my way of getting at the answer to the underlying question.

For those of you who have listened to an acoustically treated room WITH decoupled walls/ceilings and a room WITHOUT decoupled walls/ceiling, did you notice much of a difference ? (likely an apples to oranges comparison since no two rooms are alike but general impressions are OK)

For those of you who did NOT build a room within a room, do you have any regrets, concerns, complaints ? Did you ever wish you spent the extra time/money to do it or are you content with your current build ? (are we ever "content" with home theater !)

Is the room within a room all about keeping outside noise out and inside noise in ?

I understand that I can always upgrade projectors, speakers, chairs, etc but not the shell unless I start over again. I'd love to hear feedback from folks that went down this road. In the end, I know it's my decision, it's personal, it's about my tastes and preferences, etc but I enjoy learning from the perspective that others can give.
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post #2 of 18 Old 06-13-2012, 08:03 PM
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I've built them for clients both ways. Without any scientific measurement I can honestly tell you that if I ever build another personal theater it will use clips and channel. The sound isolation is superior both ways in and out. In the scheme of things if you are already using double layers and Green Glue using clips and channel is a small expense. You can install them on the walls and ceiling in less than a day.

Most people enjoying this hobby tend to upgrade. When you reach the point of debating whether you should have more than 4 sub-woofers (yes there is such a thread) you will be glad you isolated the room.
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post #3 of 18 Old 06-13-2012, 08:13 PM - Thread Starter
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I had to ask because I know that it is a best practice but I'd like to know too if good is good enough or will only great do. It's like my desktop PC. I know more RAM is better, bigger hard drive and faster processor are better but does that mean it will be better for me if I do casual web surfing and a few applications. There is a point of diminishing returns in all things and I was trying to get a sense of whether or not this building technique was a leap in performance or a small jump.

Thanks for responding. Especially since you've built several theaters.
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post #4 of 18 Old 06-13-2012, 08:20 PM
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It is a small step but in an area of critical importance to me, containing the rumble.
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post #5 of 18 Old 06-13-2012, 08:44 PM
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Whether or not its important would also depend on whats on the other side of the theater walls - infant's bedroom, or vacant garage, or attached neighbors.
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post #6 of 18 Old 06-13-2012, 09:04 PM
 
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Brad raised the critical question!

How much isolation, sound transmission is required.

You need to quantify this, as from that number there are various objective design topologies that can be examined to determine just what construction can be used to achieve just what you need - as there is no point to over-designing with the large associated costs involved.

You can measure the amount of isolation required by generating broadband pink noise signal in the room at a given gain (ideally the loudest you will anticipate playing program material) measured at the boundary surface.

Then go into the adjoining spaces of interest and measure near, but not touching the wall surface in those spaces as well.

The difference provides the amount of existing isolation.

From there you can determine what the desired/needed maximum level that can be tolerated in the adjoining spaces and from that determine the amount of additional/total isolation needed relative to what you have.

You can then examine any number of industry certified documents of proven construction techniques certified to achieve the required amount of gain reduction.

In this way you can plan and build for real needs and you will reduce the costs associated with overbuilding as well as using guesswork in determining the construction strategy necessary to achieve your goal.

If you need a list of such reference documents, PM me and I will send a copy.
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post #7 of 18 Old 06-14-2012, 06:27 AM
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There are multiple approaches to "how much is enough". One published "Best Practices" metric is you don't want to raise the ambient noise floor in an adjacent occupied room by more than 3dB (using an NR, NC, NCB curve). That, of course, doesn't account for preference or a specific need. In general playback spaces, you'd generate full bandwidth pink noise at -20dBFS in the playback space and then measure the noise floor in adjacent spaces comparing that to your previous ambient measurement. Achieving NR20 within your playback space is not easy; but, achieving that suggested level of isolation from adjacent spaces in the structure is considerably more difficult. For in room audio quality, you do want to get to NR20 inside the room. The level of noise attenuation outside the room gets very much into what you want to achieve, what your budget will tolerate, and, in many respects, your perception of the result.

There are no "certified" construction methods. There are however lab tested construction methods and materials which can provide guidance with respect to methods and materials. Note, however, that controlled NVLAP lab test conditions are entirely different than what is achieved under field conditions. When reviewing materials/construction methods, ignore STC ratings. Search out the original lab test results showing the TL (Transmission Loss) values by frequency band. Also, do not be tempted to mix, match and add the values together between two different materials or constructs. It doesn't work that way...the properties of a given barrier are very unique to that specific barrier (construction and materials).

There is certainly a "diminishing" returns component ... the last 10% of improvement can easily be 70% to 80% of the cost.

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post #8 of 18 Old 06-14-2012, 07:11 AM
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Bitten: you asked about whether using isolation methods to build a room withing a room is worth the effort you need to keep in mind that all of the effort that goes into a clip and channel room is wasted if you don't pay attention to the other details.

Plan a design that minimizes penetrations in the drywall bunker, locate switches, outlets and light fixtures inside the room using columns, stage and riser as locations for electrical boxes. If you must install an electrical gang box or recessed lighting, plan for backer boxes or putty pads to avoid turning your room into swiss cheese. Bring all your wiring into the theater through small holes and caulk around the holes and wires.

Think about your HVAC. Plan duct work that doesn't transfer sound to the rest of the house. Plan to address the holes you cut into the room to bring the ductwork into the theater. If you can run your duct work and plenums inside soffits running longitudinally and separated from the entrance points you can reduce the sound escaping. Line the soffits with acoustically absorbent material. Plan enough HVAC, you will need to cool the theater in the winter. Be aware that air flow through the ducts and vent grills can be very noisy in an otherwise quiet theater room You need to oversize your ductwork and plenums to avoid this problem.

Frame and drywall a basic box first. Build the stage, riser, soffits and columns inside the drywall bunker

Fill the stage with sand and leave a gap between the framing and the finished walls.

Buy a 1 3/4 thick solid core door on a custom jam to accommodate your extra thick walls. Plan for perimeter door seals and an automatic door bottom. See Ted. For even better isolation use two doors or a specially designed door See Dennis.

Other things, Use a 4x4 ft (or bigger) piece of 5/8 plywood as the first ceiling layer in the area where the projector will be hung. Put an outlet in the plywood with an old work box and back butter it with a putty pad just before you lift the plywood into place. Run a 1 1/2 to 2 inch electrical conduit from the equipment location to the projector area. Cut a hole in the plywood for the conduit.
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post #9 of 18 Old 06-14-2012, 07:38 AM
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Regarding the assertion that we first need to determine isolation needs, etc, etc, most people understand that their room will make a bunch of noise, especially bass, and they build based on best practices and arm for bear.

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post #10 of 18 Old 06-14-2012, 08:33 AM
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I'm a little biased as I intend to isolate my space, but it is a decision you have to make based on your goals. IIRC, Tony123 built a room with no isolation, and his only complaint is his DTS-10's can cause his walls to rattle. I don't want to put (anymore) words in his mouth, so you might try to message him and see if he can give you some feedback from the other side of the coin.

All that said, sound isolation is one of those things you can't go back and fix. So think long and hard about it before you decide one way or the other wink.gif

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post #11 of 18 Old 06-14-2012, 10:00 AM
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Quote:
Originally Posted by Ted White View Post

...most people understand that their room will make a bunch of noise, especially bass, and they build based on best practices and arm for bear.
I'm with Ted here. I've been trying to get my head around all these sorts of things lately too, and there just is no way to predict the details of what is enough and what will meet your expectations. For instance, in my case, I have always planned on fully isolated wall and ceiling structures, double drywall, and green glue, but now having considered the big picture I'm considering adding clips and channel. Why would I want to regret a decision like that? It would haunt me every time I heard rumbling from outside the theater or the hum of the attic air handler while I watch a movie. You've got to draw a line somewhere, but I won't draw it before sound isolation.
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post #12 of 18 Old 06-14-2012, 11:19 AM
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On the various recording studio forums, it's common for the local form folks to ask "how much sound isolation do you need?" Inevitably the answer is "as much as I can." Not sure why the question even gets asked.

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post #13 of 18 Old 06-14-2012, 12:15 PM
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From what I've read (and I've read a lot) it seems like an all or nothing sort of deal. If you do some, sure, you'll see some improvement. But I would personally always regret not going the whole nine yards.

So, if you are truly not concerned with soundproofing, and that means both sound getting in so that you have to turn up the movies or sound getting out and keeping the kids awake, you might be happy spending the money elsewhere. However, if you are planning DD+GG anyway, it doesn't seem like it would a significant amount to build a room within a room using conventional lumber.

Also, have you compared the cost of clips+channel to a lumber room within-room implementation? If you are trying to cut costs, maybe one of the cheaper clips could be used rather than the top of the line whisper clips?

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post #14 of 18 Old 06-14-2012, 12:33 PM
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Let me start off by saying that I do not have a sound isolated HT. It is just my wife and I so we were not as concerned about waking a baby in the next room. The room sounds great and I am extremely happy with the audio performance of my set up and there are no rattles in the walls that was mentioned in an earlier post.

I have been in a very high end HT that has isolated walls and the owner says that sound still escapes.

There have been a few occasions were my wife was down stairs and she could really hear the noise coming through the walls from our HT.

So here is my two cents on room isoluation. If I were to do it all over again I would isolate the room. One reason is every once in a while I wonder how much noise is going outside and do my neighbors hear it when walking by... Also the less sound that comes into a HT the more of the sound track you can hear. How much you really notice can be address by others here. However if you do not isolate the room you can still achieve outstanding audio performance IMHO. If not then everyone would do it. Take a look at how much you are going to put into this, $$$$ wise. If it is getting up there isolation becomes a smaller $ amount in the over all project cost.

Also take Big's experience and advise into account. He is a wealth of valuable information!biggrin.gif

Best of luck,

Jim
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post #15 of 18 Old 06-14-2012, 12:39 PM
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Quote:
Originally Posted by J_P_A View Post

If you are trying to cut costs, maybe one of the cheaper clips could be used rather than the top of the line whisper clips?

We sell FAR more of the lower-priced clips than the expensive ones. Probably 8 to 1

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post #16 of 18 Old 06-14-2012, 02:43 PM
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I have been in a very high end HT that has isolated walls and the owner says that sound still escapes.
Of course it does, for any number of reasons, not the least of which "sound proof" on planet earth is massively expensive to obtain. Now, on the space station, not so hard.

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post #17 of 18 Old 06-14-2012, 03:24 PM
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I was in an "IMAX" (Regal's fake IMAX) theater yesterday waiting on Prometheus to start. The booth crew had forgotten to turn on the sound for the digital preview ads (thankfully), so it was very quiet in there. You could hear bass from other houses. My point is total sound containment is not achievable, but every little bit helps. And, the last remaining problem will be bass.
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post #18 of 18 Old 06-16-2012, 11:46 AM
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As someone who recently finished my theater, I'll add my opinion.

I love every part of my room; the big screen, big sound, lighting, absolutely everything about it is awesome. But, what really sets it apart and makes it special when compared to every other "movie room" that I've been in is the sound isolation. Closing the door and having everything go silent is a strange feeling. It's like you've stepped out of the house and into your own little world.

My sister had a birthday party yesterday and I had no idea they were even there. Then I watched a movie late last night when the rest of the family was asleep at near reference levels and got no complaints the next morning. Being able to use the room to its full potential at any time without distracting others or being distracted yourself is easily the coolest part of the theater.

I say build it right the first time and do either room within a room or clips and channel. You won't regret it.

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