Should I use decoupling? - AVS Forum
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post #1 of 10 Old 01-03-2012, 01:23 AM - Thread Starter
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I'm going through the planning (well almost starting the build phase) and have stumbled across this forum again.

Why does everyone seem to use 'decoupling' in their theatre builds? My basic understanding is that it is used to reduce energy transfer into other area's of the house. Is this correct? I have double and single brick walls on the 4 sides of my theatre room, and a foot of concrete above and below. The noise reducing requirement is not a concern for me and I would prefer not to spend the money on the required materials, should I still be pursuing this course?

Here's a plan layout of the room if anyone is interested.

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post #2 of 10 Old 01-03-2012, 01:28 AM
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I'd still use clips and channel - makes the impedance the same (acoustic benefit)

I'd also change those doors to a single door - otherwise all the soundproofing in the world in the walls wont save you

Clips and channel will go over those windows too - another problem solved

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post #3 of 10 Old 01-03-2012, 01:41 AM - Thread Starter
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Thanks Elill, I was reading your build thread earlier. It looks very well planned and thought out. Paul Spencer from the SNA forums was giving me some good idea's with respect to bass traps earlier in the year. It's nice to see us Aussies looking after each other!

The area with the double doors is going to be the screen wall. I have most of the timber and was planning to start laying in the framing over the next few weeks. I wanted to leave the doors in situ, in case we want to use the room for something else in the future. Unlikely, but WAF unfortunately has played a part in this decision.

I'm still at a bit of a loss as to why you would still clip this room? By doing so, it would be a significant investment in time and money to do so, the bulkhead was already installed as part of the house build and would need to be removed and rebuilt as well. Blanking the rear windows is a good idea however.

I was saving all this for a build thread, but wanted to actually have somethign to post first. Here's a few pictures of the room as it stands, the rack has been moved under the stairs. Its not a big room, at 4.7m x 3.7m I would be trying to maximise the space as much as I can. +2.4m ceiling should help a little.



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post #4 of 10 Old 01-03-2012, 02:50 AM
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Bugger about the ceiling/drywall......I'd not want to take it down either....but.......

Have you got a good sub you can put in there to test out isolation?

I'd put the screen on the window wall

Your room is a little smaller than mine (only slightly), what layout are you thinking? Ideally you're talking 2 seats only......you can try a second row but you're compromising somewhere, especially with the door in that position

What'd I be doing? Paying Dennis to give me a layout/treatment plan and not stressing about getting it wrong.....this is what I'll do in a couple of years time when we have coin to blow on it.....

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post #5 of 10 Old 01-03-2012, 07:15 PM - Thread Starter
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Quote:
Originally Posted by Elill View Post

Bugger about the ceiling/drywall......I'd not want to take it down either....but.......

Have you got a good sub you can put in there to test out isolation?

Yes, I have a custom Fi sub based around the Adire Audio Sadhara that I built that sounds nice. I also have a calibrated Behringer ECM8000 mic and USB Mixer so I can measure the room response. I'm still curious (learning) about how measuring is important BEFORE I start construction. My parents house has similar construction to mine so I intend to go there and see how much noise is transferred into their house before I make a decision.

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I'd put the screen on the window wall

Your room is a little smaller than mine (only slightly), what layout are you thinking? Ideally you're talking 2 seats only......you can try a second row but you're compromising somewhere, especially with the door in that position

What'd I be doing? Paying Dennis to give me a layout/treatment planand not stressing about getting it wrong.....this is what I'll do in a couple of years time when we have coin to blow on it.....

These are the layouts I have been considering.


If I put the screen on the window wall, I would not be able to install a bass trap on the front LHS.

The seats that I have shown in the basic markups are 3 and 4 seat models. I put 2 rows in the long layout so you could see how cramped that would become. I would probably stick with only one row. The wide layout would be able to handle a 4 seater comfortably.

As this is my first theatre, I understand that I am going to make a few mistakes, and understand that I will need to make a few compromises as well. This is our first home so I'm trying to be realistic with budget and expectations, so perhaps later in life I might be able to go with a more 'no holds barred' approach that is more common on these forums.
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post #6 of 10 Old 01-03-2012, 08:17 PM
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The idea of putting the sub in there now is just to see how good the current isolation is - put it in, run a low, loud test tone, shut the door and go for a walk around the house. if you're not happy get some advice on how to fix.

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Originally Posted by Gonadman2 View Post

If I put the screen on the window wall, I would not be able to install a bass trap on the front LHS.

There are other ways of bass trapping than stacking stuff in corners, that are neither complex or expensive, you 'just' need to know how to build them/where to put then. This avoids putting "stuff" in corners

What I have observed over my years here is that rooms that are well designed and laid out get used often. Those that aren't dont. Then 2-3 years later we see people ripping it out and starting again.

Best of luck with the project.

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post #7 of 10 Old 01-03-2012, 08:24 PM - Thread Starter
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Quote:
Originally Posted by Elill View Post

What I have observed over my years here is that rooms that are well designed and laid out get used often. Those that aren't dont. Then 2-3 years later we see people ripping it out and starting again.

Best of luck with the project.

Great advice. I really like your suggestion re: Installing the front end on the window wall. This was my original plan for this room. I was talked out of it because of the lack of modal control. I think I'll revisit it.

Thankyou for your advice. Its nice to throw idea's around with a level head.
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post #8 of 10 Old 01-10-2012, 06:37 PM - Thread Starter
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Quote:
Originally Posted by Elill View Post

I'd still use clips and channel - makes the impedance the same (acoustic benefit)

I'd also change those doors to a single door - otherwise all the soundproofing in the world in the walls wont save you

Clips and channel will go over those windows too - another problem solved

Ok, so I've done bucketloads of reading on the subject and this Harman Paper has convinced me that I will need Decoupling to reduce ringing in my very solid room.

So I have an couple of simple questions regarding my particular application:
Almost every thread that I have read about that has a 'room within a room' installation uses stud walls with insulation in them. As I don't have stud walls, I am thinking that I attach the isolation clips directly to the brick/concrete? This would not leave much room for fibreglass insulation. Is this ideal?

When Butting the drywall to the floor, is it desirable to use a layer of closed cell foam to ensure that there is no mechanical coupling, or do you guys just cut the dry wall a little shorter? Basically, how important is the seal at the floor?

Thanks in advance
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post #9 of 10 Old 01-10-2012, 07:30 PM
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I'd go clips straight onto block wall if I did mine again. Probably dont need insulation in there?

No point in doing the walls if you dont do the ceiling.......

Fire rated or acoustic sealant is what you use for the joins.

How particular do you want to get with the floor? ideally do what PeterM is doing - angelstep from acoustica and then two layers of sheeting with GG in between.

You doing GG/DD? You can buy it cheaper from the US and ship here.....if you want to buy locally call Ultrafonic and ask advice/buy from them

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post #10 of 10 Old 01-10-2012, 08:18 PM - Thread Starter
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Quote:
Originally Posted by Elill View Post

I'd go clips straight onto block wall if I did mine again. Probably dont need insulation in there?

No point in doing the walls if you dont do the ceiling.......

Fire rated or acoustic sealant is what you use for the joins.

How particular do you want to get with the floor? ideally do what PeterM is doing - angelstep from acoustica and then two layers of sheeting with GG in between.

You doing GG/DD? You can buy it cheaper from the US and ship here.....if you want to buy locally call Ultrafonic and ask advice/buy from them

From what I have read the insulation forms an absorption layer in the cavity between the isolated surface and wall. The only downside is that I would lose 180mm across the walls, and it would increase cost. I could still split some batts and install them in the depth of the Furring channel + clips.

I will be using the Green glue in between the layers of Gyprock (I think they call it drywall on here), and I will definitely be doing the ceiling as well. The ceiling currently has a gyprock layer screwed into timber battens cast flush into the first floor slab. I was hoping to be able to screw the isolating clips straight into the battens.

You are saying I need fire rated acoustic sealant for the joins - what joins are you referring to here? I'm guessing these are the corners where the gyprock comes together so there is no losses through the gaps?

For the floor I was just going to carpet it. There is going to be a stage at the back and front, so only a small area will actually be carpet on concrete.

Here's a little model I did up. It is a constantly evolving work, in progress at the moment, and I'm still trying to get my head around the bob golds calculator and room modes. Still tossing up whether to go with one or 2 rows at the moment. I was going to lay everything out this weekend and see how it works in the room. The first row would be 3m from the screen which is just about perfect for the ~115" or so I will have available. The second row is not in an ideal position but it would be very nice to include.



Perhaps I should move this to a build thread?
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